Therapeutic Potential of Centhaquine Citrate, a Selective Alpha-2B Adrenoceptor Agonist, in the Management of Circulatory Shock

Abstract

Shock is a life-threatening condition marked by inadequate tissue perfusion and organ dysfunction with high morbidity and mortality. Activation of the sympatho-adrenergic system is pivotal in response to all four major categories (i.e., hypovolemic, distributive, cardiogenic, and obstructive). In addition, exogenous vasopressors are often used to maintain organ perfusion pressure and decrease the size of the intravascular compartment. These agents preferentially constrict the arterial system but may lead to microcirculatory failure, especially at higher doses. This review outlines the sympatho-adrenergic system response after shock, discusses various vasopressors currently used as resuscitative agents, and reports the rationale for using a predominant venous vasopressor in shock. We also discuss the preliminary evidence for and ongoing research into a novel venous vasopressor, centhaquine citrate.

Key Points

Traditional resuscitation of shock often involves a strategy of perfusion pressure management with exogenous vasopressors, all of which are primarily afterload-increasing agents or arterial constrictors.

Excessive increase of arterial afterload may lead to microcirculatory failure.

The novel agent centhaquine citrate acts via a predominantly venous vasoconstriction pathway that may allow for increased venous return and cardiac output while preserving microcirculation.

Background

Shock is a state of circulatory failure leading to a severe decrease in tissue perfusion associated with impaired oxygen utilization and, ultimately, multiorgan failure [1–4]. Tissue hypoperfusion may lead to ischemia/hypoxia and impaired cellular function, inhibiting enzyme activity and disrupting normal physiological cellular processes [5]. Among factors contributing to shock, decreased vascular tone is a common feature of distributive shock but may also develop in hypovolemic and cardiogenic shock.

Prolonged arterial constriction as part of an endogenous response or exogenous vasopressor support can lead to inadequate flow and microcirculatory failure, thereby negating any benefit of increased arterial pressure and an increased risk of downstream organ system injury [6].

This narrative review discusses various available vasopressor-based resuscitative agents for managing shock and the rationale for using venous vasopressors, along with preliminary data on centhaquine citrate, a novel α2 adrenoceptor (AR) agonist.

The Role of the Inter-territory Vascular Distribution of Catecholamine Receptors

The distribution of different types of ARs in various organs and tissues is highly distinct. Briefly, α1-ARs are predominantly found in vascular smooth muscle cells (SMCs), endothelial cells, cardiomyocytes, prostate SMCs, and the brain. α2-ARs are present in the autonomic ganglia, sympathetic neurons, central nervous system, platelets, kidney tubular epithelium, pancreas, vascular SMCs, and gastrointestinal SMCs. β1-ARs are expressed in cardiomyocytes, kidney SMCs, and adipocytes, and β2-ARs are found in vascular SMCs, endothelial cells, cardiomyocytes, gastrointestinal SMCs, adipocytes, pancreas, eyes (ciliary epithelium), liver, skeletal muscle, and SMCs present in the lungs, uterus, and bladder. Additionally, β3-ARs are present in cardiomyocytes, adipocytes, endothelial cells, bladder SMCs, gallbladder, retina, and epithelial cells [7, 8].

The arrangement of α1 and α2 subtypes (α2A, α2B, and α2C) in the sympathetic nervous system and target tissues is important for the regulation of the constriction/relaxation of the blood vessels. The α1 subtype is post-synaptic, whereas the α2A and α2C subtypes are situated mostly pre-synaptically, and the α2B subtype is situated extra-synaptically (blood vessel wall) [9–13]. Moreover, the distribution of α2A-ARs and α2B-ARs within the vasculature varies significantly according to the specific vascular bed and vessel size [14, 15]. Large arteries (e.g., the aorta, pulmonary artery, mesenteric artery, etc.) have a substantial presence of α1-ARs, which is regulated by α2A/C presynaptic ARs, and control arterial contractility, vascular resistance, and blood pressure [16, 17]. On the other hand, α2-ARs (α2A, α2B, and α2C) are notably abundant in peripheral veins and comparatively less present in large arteries [18, 19]. As the majority of extrasynaptic α2 are α2B subtypes, the presence of α2B receptors in veins highlights their predominant involvement in the constriction of veins essential for venous return and maintenance of adequate cardiac preload and cardiac output (CO) [8, 13, 20]. A deeper understanding of the distribution and signaling of α2B receptors would help in the development of more efficient resuscitative agents with better capacity to increase the cardiac preload and CO in shock.

Organ Distribution

α2B-ARs are widely distributed across various tissues in the human body. They are primarily found in the brain, ciliary body, retina, vascular smooth muscle, and peripheral organs such as the adrenal glands, liver, kidneys, and spinal cord. In the central nervous system, they are expressed in the cortex, cerebellum, pons–medulla, and hypothalamus, with notable concentrations in the thalamus, hippocampus, and cerebellar Purkinje cell layer. In the eye, they are present in the ciliary body and retina. In the ciliary body, they are reported to be in the nonpigmented epithelium and ciliary muscle, whereas in the retina they are found in neurons and glial cells, with expression in the dendrites, axons, and cell membranes [21–23].

Downstream Signaling

The α2B-AR is a G protein-coupled receptor primarily coupled to Gi/Go proteins. Upon activation, it undergoes a conformational change and facilitates Gi/Go protein recruitment, leading to GDP–GTP exchange on the Gαi subunit, which then dissociates from the Gβγ complex. The Gαi subunit inhibits adenylyl cyclase, reducing cyclic adenosine monophosphate levels and limiting protein kinase A activation (limiting protein kinase A downstream signaling, including glycogenolysis). In contrast, Gβγ subunits modulate mitogen-activated protein kinase signaling and ion channel activity. Gαi activation in vascular SMCs triggers RhoA activation. RhoA activates Rho-associated protein kinase, leading to myosin light chain phosphorylation and vasoconstriction, increasing vascular resistance. On the other hand, Gβγ subunits activate Src family kinases, triggering the Ras-Raf-MEK-ERK cascade, where ERK1/2 translocates to the nucleus, promoting cell survival and proliferation. This pathway contributes to vascular smooth muscle growth and hypertension. The α2B-AR signaling also activates phosphoinositide 3-kinase via βγ-subunits or receptor tyrosine kinases. Phosphoinositide 3-kinase converts PIP2 to PIP3, activating protein kinase B, which regulates cell survival, glucose metabolism, and endothelial function. The α2B-AR is also known to undergo short-term desensitization through G protein-coupled receptor kinase-mediated phosphorylation, leading to β-arrestin recruitment and receptor internalization via clathrin-coated pits, ensuring receptor recycling or degradation. These signaling pathways could be modulated using agonists (e.g., centhaquine, (−)-dibromophakellin) [24] and antagonists (e.g., ARC-239, imiloxan) for α2B-AR.

Traditional AR Agonists

Commonly used vasopressors are categorized into adrenergic and non-adrenergic types. They affect both arteries and veins [25], and their use may be associated with a risk of cardiac arrhythmias, organ ischemia, and cellular metabolic imbalance [26]. Inopressors (epinephrine, norepinephrine), dopamine, and phenylephrine act on α-ARs and/or β-ARs [27, 28]. A list of commonly used vasopressors as resuscitative agents is provided in Table 1.

Table 1.

Details of commonly used vasopressors as resuscitative agents in shock

Vasopressors	Dose and administration	Half-life	Mechanism of action
			Receptors	Vascular effects	Cardiac preload and afterload	Other effects [29–35]
Norepinephrine	0.01–0.5 µg/kg/min	2–2.5 min	α1, α2, β1	Venous constriction: ↑ stressed volume, ↑ venous return; arterial constriction	↑ Preload, ↑ afterload	↑ Myocardial contractility, ↑ HR
Epinephrine	0.01–0.5 µg/kg/min	< 5 min	β (0.01–0.1 µg/kg/min); α (> 0.1 µg/kg/min)	Venous constriction, arterial constriction	↑ Preload	↑↑↑ HR, ↑↑ myocardial contractility; deleterious effects on tissue perfusion at higher doses
Dopamine	0.5–2 µg/kg/min (low dose); 2–10 µg/kg/min (medium dose); 10–20 µg/kg/min (high dose)	2 min	D1 D2 (1–5 µg/kg/min); β (5–10 µg/kg/min); α1 (10–15 µg/kg/min)	Low dose: acts on visceral vasculature and produces vasodilation. Medium dose: stimulates contractility and electrical conductivity in the heart, leading to increased CO. High dose: causes vasoconstriction and increases BP via the α1, β1, and β2 ARs	↓ Afterload (LV)	↑↑ HR, ↑ myocardial contractility and electrical conductivity
Phenylephrine	0.4–4 µg/kg/min IV bolus or continuous infusion	2–3 h	α1	↑ SVR, ↑ BP	↑ Afterload	↓ CO in preload independent heart, ↑ CO in preload-dependent heart
Angiotensin II	5–200 ng/kg/min IV administration through central venous line	< 1 min	AT1, AT2	Venous constriction, arterial constriction	↑ Afterload	↑ Myocardial contractility [36]; ↑ myocardial blood flow [37]; ↑ BP and CO [38, 39]
Vasopressin	0.01–0.07 (avoid higher doses up to 0.07 units/min)	5–15 min	V1a, V1b, V2	Venous constriction, arterial constriction	↑ Afterload	Platelet aggregation, ↓ NO; potentiation of endogenous vasoconstrictors
Centhaquine	0.01 mg/kg in 100 mL saline 0.9% over 1 h IV infusion	0.71–1.62 h	Peripheral α2B, central α2A	Venous constriction: ↑ stressed volume, ↑ venous return, arterial dilation	↑ Preload, ↓ afterload	↑ CO, ↑ MAP; renal protection by HIF activation

AR adrenoceptor; AT_1/2 angiotensin II receptor type 1/2, BP blood pressure, CO cardiac output, h hour(s), HIF hypoxia-inducible factor, HR heart rate, IV intravenous, LV left ventricular, MAP mean arterial pressure, min minute(s), NO nitric oxide, SVR systemic vascular resistance, V1a/b Vasopressin receptor V1a and V1b, V2 Vasopressin Receptor V2; ↑ indicates increase, ↓ indicates decrease↑↑ and ↑↑↑ indicate relatively more increase than ↑

Inopressors (epinephrine, norepinephrine) act primarily on the α-ARs and β1-ARs and increase both arterial constriction and heart rate. However, excessive arteriolar constriction (particularly in the splanchnic region) could have detrimental ischemic adverse effects (AEs) [26, 29, 40, 41]. Activation of cardiac β1-ARs by inopressors and other vasopressors is known to cause cardiac arrhythmia or atrial fibrillation.

In-depth molecular signaling studies have shown that norepinephrine has a better affinity to α2-ARs than to α1-ARs or β-ARs [42, 43]. Its vasoconstrictive regulatory function was abrogated in α2A knockout mice but not in α2B or α2C knockouts [44]. Moreover, the use of pharmacological antagonists demonstrated the role of α2A in regulating the release of norepinephrine from presynaptic sympathetic neurons as part of a feedback loop [9]. Mice lacking α2A showed severely impaired presynaptic feedback loop regulation [10, 11], and α2C was recognized as an additional presynaptic regulator in all examined central and peripheral nervous tissues [10–12, 45]. Overall, the arrangement of α-ARs in presynaptic, post-synaptic, and extrasynaptic regions seems to be α2A/α2C pre-synaptically, α1 post-synaptically, and α2B extrasynaptically. The binding of agonist to α2B induces constriction in the blood vessels as a sympathetic response, whereas binding of the same agonist to α2A/α2C regulates the release of neurotransmitters (e.g., norepinephrine, serotonin, etc.) to post-synaptic α1, and together they modulate constriction in arteries to maintain homeostasis and/or meet physiological demands. Nonetheless, activation of presynaptic α2A/α2C starts a negative feedback loop and inhibits the secretion of neurotransmitters required to activate post-synaptic α1; thus, it curtails the sympathetic response and reduces arterial constriction, which could lead to a biphasic effect on blood pressure with initial α2B-mediated hypertension and later an α2A/α2C-mediated hypotension phase [11, 14, 44]. Hence, the selective activation of extrasynaptic α2B appears to be independent of this negative feedback loop and could serve as a target for developing more effective resuscitative agents for various types of shock involving episodes of hypotension.

Rationale for Selective α2B-AR Agonists

Veins act as capacitance vessels and store 70% of the total blood volume [46, 47], which consists of stressed and unstressed types [48]. Stressed volume is hemodynamically active and influences venous return and cardiac preload, whereas unstressed volume serves as a physiological inert reservoir [49–52]. The venous tone is mainly regulated by the sympatho-adrenergic system, which induces venoconstriction, converting unstressed to stressed blood volume, leading to increased venous return, cardiac preload, and CO [47, 49, 50, 52]. Cutaneous and splanchnic veins actively contribute to blood reservoirs. The cutaneous venous tone responds to temperature and stress, whereas splanchnic veins are triggered by changes in arterial blood parameters and blood pressure [49]. Although catecholamines modulate venous tone, most of this effect is in the cutaneous and splanchnic beds rich in α1-ARs [53, 54]. As described, the entire venous system is rich with α2B-ARs, and targeting them to induce venoconstriction would decrease compliance in most of the venous system, increasing systemic venular resistance and consequently increasing venous return and CO while not impairing the forward flow or the microcirculation that is a typical effect of arterial constrictors. This mechanism would be potentially beneficial in both hypovolemic/hemorrhagic and septic shock where the predominant resuscitation strategies are based on volume (hypovolemic shock) and volume plus arterial constrictors (septic shock). Use in the setting of significant hypotension and vasodilatory states such as septic shock may need a background of low-dose arterial vasoconstrictors and centhaquine citrate (2-[2-[4-(3-Methylphenyl)-1-piperazinyl]ethyl] quinoline citrate; hereafter “centhaquine”) as an adjuvant.

Preliminary Data on Centhaquine, a New α2B-AR Agonist

Centhaquine is a novel α2B-AR agonist being investigated for the treatment and management of shock (Fig. 1). Preliminary reports have shown promising results regarding its safety and efficacy in both animal and human studies [30, 55–65] (Table 2). It has demonstrated good tolerability and minimal AEs, indicating a high safety profile and making it an attractive candidate for various other types of shock management. Following successful early-phase clinical trials in India [30, 55], the US Food and Drug Administration has recently approved a phase III trial of centhaquine (marketed as Lyfaquin^® in India [30, 55]) in patients with hypovolemic and/or hemorrhagic shock.

Fig. 1.

Mechanism of action of centhaquine citrate involved in patient resuscitation after shock. Centhaquine activates adrenergic α2B signaling (lower left panel) and induces venous constriction, increasing venous return to the heart and enhancing cardiac output in patients with shock. Centhaquine may also interact with central α2A receptors (upper right panel) and reduce the central sympatho-adrenergic action by decreasing norepinephrine secretion, leading to increased tissue perfusion.

Table 2.

List of important centhaquine studies

Sl. #	Study, year	Species (n)	Aim of the study	Brief study details and main findings	Proposed mechanism of action
1	Bhatnagar et al., [66] 1985	Rabbit	Effect of centhaquine on spontaneous and evoked norepinephrine release from isolated perfused heart	Centhaquine affects NE release from the rabbit heart. Centhaquine 0.1, 1.0, and 10.0 µg/mL initially increased then inhibited spontaneous NE output. It significantly suppressed NE release evoked by KCl, DMPP, and acetylcholine but did not affect NE release induced by tyramine or amphetamine. Findings suggest that centhaquine primarily inhibits neuronal NE release	The biphasic effect of centhaquine on NE concentration (initial increase and later decrease) could be because centhaquine predominantly inhibits the neuronal NE release but does not affect NE release from peripheral nerves
2	Srimal et al., [88] 1990	Rat (55) and cat (no. of exp. 169)	Pharmacological studies on 2-(2-(4-(3-methylphenyl)-1-piperazinyl)ethyl) quinoline (centhaquin). I. Hypotensive activity	Centhaquine lowered BP and reduced HR in a dose-dependent manner (0.01–1.0 mg/kg IV or 1.0–2.5 mg/kg intraduodenally) in cats. The hypotensive effect was insignificant in spinal transected cats but more marked in deafferented and vagotomized animals. Localization of centhaquine to brain by intravertebral arterial injection (5–10 µg) or by topical application to the exposed ventral surface of the medulla or floor of the fourth ventricle caused hypotension and bradycardia and reduced the excitability of the vasomotor loci. It was also effective in rats after single and multiple dosing	Centhaquine seems to act centrally to reduce BP
3	Gulati et al., [67] 1991	Rat (10)	Effect of repeated administration of centhaquine, a centrally acting hypotensive drug, on adrenergic, cholinergic (muscarinic), dopaminergic, and serotonergic receptors in brain regions of rat	Oral administration of centhaquine 0.1 mg/kg for 2 mo in rats led to changes in central α-adrenergic, dopaminergic, and 5-HT1 receptors and a significant decrease in mean BP. Centhaquine had no effect on Bmax or Kd values of 3H-dihydroergocryptine binding in the cerebral cortex and corpus striatum, it significantly increased Bmax in the hypothalamus (52%) and medulla (86%) without altering Kd values. Centhaquine did not affect β-adrenergic, muscarinic cholinergic, or 5-HT2 receptor binding in any brain region. However, it reduced the Bmax of 3H-spiroperidol binding to dopaminergic receptors in the cortex (25%) but had no effect in other regions. Similarly, centhaquine had no impact on 5-HT1 receptor binding in most regions but increased Bmax by 41% in the medulla without altering Kd values	Centhaquine influences central neurotransmitter receptor systems, particularly in the medulla and hypothalamus, which may contribute to its hypotensive effects
4	Gulati et al., [68] 1993	Rat (24)	Central serotonergic uptake mechanisms in hypertensive rats: effects of clonidine and centhaquine	The study examined the binding of [3H]paroxetine, a ligand for 5-HT-uptake sites, in different brain regions of normotensive WKY rats and SHR. SHR exhibited a significant 27.16% reduction in [3H]paroxetine Bmax in the midbrain compared with WKY; Kd remained unchanged. No significant differences in Bmax or Kd in other brain regions. Study also assessed the effects of the hypotensive agents clonidine and centhaquine on [3H]paroxetine binding. Clonidine had no effect; centhaquine displaced [3H]paroxetine binding in a concentration-dependent manner, similar to imipramine, a known 5-HT uptake inhibitor. Centhaquine was more potent than imipramine in displacing paroxetine, with an IC50 value 10 times lower in the cerebral cortex and 4 times lower in the brainstem	By inhibiting 5-HT uptake, centhaquine may enhance serotonergic signaling, which could play a role in its hypotensive effects through central modulation of sympathetic activity
5	Gulati et al. , [69] 2011	Rat (50)	Effect of Centhaquin on norepinephrine requirement for maintaining blood pressure and improving survival in hemorrhage rats	The study evaluated the effect of centhaquine on NE requirements for maintaining a MAP of 70 mmHg in severely hemorrhaged rats. Blood lactate was significantly lower with centhaquine (1.65 ± 0.23 mmol/L) than with NS (4.10 ± 1.02 mmol/L, p = 0.041) at 60 min after resuscitation. The NE required to maintain MAP was substantially lower with centhaquine (17.5 µg) than with NS (175 µg) during the first 60 min, indicating centhaquine's potential to improve resuscitation efficiency	Centhaquine decreases the requirement of NE in hemorrhaged rats, possibly due to improved vascular responsiveness
6	Andurkar et al., [70] 2011	Mouse (32)	Assessment of the analgesic effect of centhaquine in mouse tail flick and hot-plate tests	Centhaquine was evaluated for its analgesic and hypothermic effects in mice and its potential to enhance morphine analgesia. In tail flick and hot-plate tests, centhaquine demonstrated dose-dependent analgesia, partially blocked by yohimbine, idazoxan, and naloxone, indicating involvement of α(2)-adrenergic, imidazoline, and opioid receptors, while endothelin ETA antagonists BQ123 and sulfisoxazole had no effect. Centhaquine did not potentiate morphine analgesia. Additionally, centhaquine induced mild hypothermia, which was unaffected by any antagonists. This study provides the first evidence of centhaquine’s analgesic properties, mediated by adrenergic, imidazoline, and opioid receptors, with no role for endothelin ETA receptors	The possible mechanism underlying centhaquine’s analgesic effects involves its interaction with α(2)-adrenergic, imidazoline, and opioid receptors
7	Briyal et al., [71] 2012	Pregnant rats (16) and neonatal rats (48)	Effect of repeated administration of centhaquine in pregnant rats on postnatal development and expression of endothelin receptors in the brain, heart or kidney of  rat pups	The study examined the effects of centhaquine on pregnant and postnatal rats. Pregnant rats in both vehicle and centhaquine groups showed steady weight gain, and centhaquine had no impact on ETA receptor expression in the heart and kidney but significantly increased its expression in the brain of postpartum rats. ETB receptor expression remained unchanged. In postnatal rats, body and organ weights (brain, kidney, heart) increased proportionally with age and were unaffected by centhaquine. ETA receptor expression was similar between groups; ETB receptor expression significantly decreased (p <0.001) by day 28 in both groups	Effect of centhaquine on ETA receptor expression in the brain of postpartum rats may indicate its potential role in neuroadaptive response in the postpartum phase; however, no effects on ETA and ETB expressions in rat pups may spare their postnatal development
8	Gulati et al. [57], 2012	Rat (36)	Study of the resuscitative effect of Centhaquine  with hypertonic saline in hemorrhaged rats	HS reduced blood lactate levels and improved CO in hemorrhaged rats. When combined with centhaquine, it led to a greater reduction in blood lactate and a more significant increase in MAP and CO. At 250 min after resuscitation, survival was 0 in the HS group but 0.8 in the centhaquine group, highlighting its superior efficacy	The enhanced efficacy of centhaquine combined with HS may be attributed to its synergistic effects on CV function and tissue perfusion, ultimately contributing to higher survival rates in hemorrhaged rats
9	Gulati et al. [72], 2012	Rat	Role of alpha-adrenoceptor in hemorrhaged rats after resuscitative with  centhaquine	This study investigated the mechanism of action of centhaquine, hypothesizing that its resuscitative effects are mediated through α2-ARs. Using pressure–volume loop analysis and blood gas measurements, centhaquine 0.05 mg/kg reduced blood lactate levels, improved CO, and stabilized BP. The resuscitative effects were significantly antagonized by α2-AR blockers, yohimbine and atipamezole, confirming the involvement of α2 receptors in centhaquine’s mechanism of action	The resuscitative effect of centhaquine may be attributed to its action on α2-ARs, which play a key role in cardiovascular regulation
10	Gulati et al. [56], 2013	Rat (12)	Efficacy of centhaquine as a small volume resuscitative agent in severely hemorrhaged rats	Centhaquine significantly reduced blood lactate levels and improved CO and MAP in hemorrhaged rats compared with HS. MAP dropped to 35 mmHg within 55 ± 6 min in HS-treated rats and within 161 ± 14 min in centhaquine-treated rats. Survival time after fresh blood administration was 79 ± 7 min in the vehicle-treated group and 105 ± 9 min with centhaquine. Overall survival time was 134 ± 12 min with HS and 266 ± 16 min with centhaquine, indicating improved survival with centhaquine	Centhaquine mediated improved CO, better MAP stability, and reduced lactate levels compared with HS; could be pivotal for better resuscitative effects of centhaquine in hemorrhaged rats
11	Lavhale et al. [59], 2013	Rat (32)	Resuscitative effect of centhaquine after hemorrhagic shock in rats	Centhaquine 0.017 and 0.05 mg/kg led to a marked improvement in survival time (291 ± 57 and 387 ± 39 min, respectively) compared with LR-100 (78 ± 10 min) in hemorrhaged rats. It also significantly reduced blood lactate levels and increased mean MAP by 55% and 59%; LR-100 led to a 29% decrease. Centhaquine increased CO by 260% and 180% and decreased SVR more effectively than LR-100. Compared with LR-300, centhaquine 0.05 mg/kg demonstrated superior efficacy in improving survival, increasing CO, and resuscitating hemorrhaged rats, highlighting its potential as an effective resuscitative agent for hemorrhagic shock	Centhaquine 0.05 mg/kg mediated significant improvement in CO and MAP and decreased SVR in hemorrhaged rats; this could explain its better resuscitative effects over LR-100 or LR-300
12	Bhalla et al. [73], 2013	Mouse	Study of signaling pathways for centhaquine-mediated antinociception in mice	This study investigated the role of α2-AR subtypes in centhaquine-induced antinociception. Antinociceptive effects were blocked by BRL-44408 (α2A-AR antagonist) and imiloxan (α2B-AR antagonist) but remained unaffected by JP-1302 (α2C-AR antagonist). These findings indicate that centhaquine mediates its antinociceptive effects through α2A-AR and α2B-AR, but not α2C-AR, marking the first report of this specific receptor involvement	α2-agonism of centhaquine may be mediated through α2A-AR and α2B-AR but not by α2C-AR
13	Kachanov et al. [74], 2014	Rat (16)	Role of centhaquine in resuscitation of endotoxic (septic) shock in rats	Centhaquine 0.05 mg/kg was evaluated for its effects on survival and hemodynamic performance in a rat model of septic shock induced by IV LPS 20 mg/kg. Centhaquine significantly increased HR (26 +/− 4% vs 14 +/− 3%, p = 0.016) and CO (70 +/− 15% vs 27 +/− 13%, p =  0.03) compared to control treatment. Also, a trend toward increased SV in centhaquine group compared to the control group was seen; however, it did not improve survival time (161 ± 16 vs. 152 ± 20 min, p > 0.05), significantly. Thus, centhaquine could be supportive with ement of cardiac performance; centhaquine did not significantly affect mortality in this septic shock model	The possible mechanism by which centhaquine 0.05 mg/kg temporarily enhances cardiac performance in septic shock may involve its role in modulating vascular tone and cardiac function. Centhaquine could provide hemodynamic support in septic shock
14	Goyal et al. [75], 2015	Human (24)	Safety and efficacy of centhaquine as a novel resuscitative agent for hypovolemic shock	This was a single-center, randomized, DB, PC phase I trial to evaluate the safety of PMZ-2010 (centhaquine) (NCT02408731) in healthy male subjects in 6 cohorts of 4 subjects each: 3 received the active drug, 1 received placebo. The SAD cohorts began with an initial dose of 0.005 mg/kg of PMZ-2010 via IV infusion, and doses were escalated based on safety and tolerability up to 0.10 mg/kg, which was determined as the MTD. In the MAD cohorts, the initial dose was 0.10 mg/kg/day (3 × 0.033 mg/kg/day) for 2 days, escalating to 2 times the MTD (0.20 mg/kg) for 2 days. The study concluded that the MTD of PMZ-2010 in humans is 0.10 mg/kg and can be safely used for resuscitative purposes	The observed safety profile and established MTD of 0.10 mg/kg suggest that centhaquine can be used as a resuscitative agent with a favorable therapeutic window
15	Reniguntala et al. [64], 2015	Rat (30)	Synthesis and characterization of centhaquine and its citrate salt and a comparative evaluation of their cardiovascular actions	Centhaquine causes hypotension and bradycardia at higher doses and acts as a resuscitative agent at lower doses. However, its water insolubility limits IV use. To address this, the citrate salt of centhaquine was synthesized and evaluated for CV efficacy compared with centhaquine. Centhaquine citrate was 99.8% pure and water soluble. In anesthetized male SD rats, centhaquine citrate produced a significantly greater decrease in MAP, PP, HR, CO, SV, and SW compared with centhaquine at equivalent doses (0.05, 0.15, and 0.45 mg/kg). At 0.45 mg/kg, centhaquine citrate reduced CO by 42.1% (p < 0.001) compared with a 20.9% reduction with centhaquine (p < 0.01). These findings indicate that centhaquine citrate has greater CV activity than centhaquine	The better CV effects of centhaquine citrate could be because of its better solubility, dissolution rate, and absorption in the body than centhaquine
16	O'Donnell et al. [61], 2016	Rat (16)	Pharmacokinetics of centhaquine citrate in a rat model	A two-compartment model was used to best fit the pharmacokinetic data for centhaquine citrate. The median (IQR) values for the Ke, V, and Kcp, Kpc were 8.8 (5.2–12.8) h⁻1, 6.4 (2.8–10.4) L, 11.9 (4.6–15.0) h⁻1, and 3.7 (2.3–9.1) h⁻1, respectively. Centhaquine citrate has a short half-life and a large V, suggesting rapid clearance from the plasma and widespread tissue distribution	Pharmacokinetic profile of centhaquine citrate in rats with a combination of rapid clearance and extensive tissue distribution may contribute to its effectiveness in modulating vascular tone and tissue perfusion, particularly in hemorrhagic conditions
17	Gulati et al. , [76] 2016	Human (24)	Human pharmacokinetics of centhaquine citrate, a novel resuscitative agent	This study aimed to determine the pharmacokinetics of PMZ-2010 (centhaquine citrate) in healthy human volunteers through a randomized, DB, PC phase I trial. Subjects received IV PMZ-2010 0.005–0.10 mg/kg, and plasma concentrations were measured at various time points up to 8 h after administration. The pharmacokinetic data were best described by a two-compartment model, with Bayesian predictions showing high accuracy (R2 = 0.94). Key pharmacokinetic parameters included a Ke of 4.1 h⁻1, V of 29.5 L, and Kcp and Kpc of 10.4 h⁻1 and 2.1 h⁻1, respectively. Results indicated that PMZ-2010 has rapid plasma elimination, and the pharmacokinetic profile aligns with previous studies in rats and dogs	The rapid clearance and distribution observed in humans may contribute to its effectiveness in clinical resuscitation protocols, where timely and efficient tissue perfusion is essential
18	O'Donnell et al. [62], 2016	Dog (4)	Pharmacokinetics of centhaquine citrate in a dog model	The pharmacokinetic parameters of centhaquine citrate were best described using a two-compartment model. The median (IQR) values for the Ke, Vc, Vp, Kcp, and Kpc were 4.9 (4.4–5.2) h⁻1, 328.4 (304.0–331.9) L, 1000.6 (912.3–1042.4) L, 10.6 (10.3–11.1) h⁻1, and 3.2 (2.9–3.7) h⁻1, respectively. These show that centhaquine citrate has a large V and rapid elimination, which is consistent with previous pharmacokinetic studies in rats, indicating efficient tissue distribution and fast clearance from the body	The pharmacokinetic profile of centhaquine citrate in dogs with a combination of rapid clearance and extensive tissue distribution may contribute to its effectiveness in modulating vascular tone and tissue perfusion, particularly in hemorrhagic conditions
19	Papapanagiotou et al. [63], 2016	Pig (20)	Resuscitative effect of Centhaquine in a swine model of hemorrhagic shock	Centhaquine 0.015 mg/kg was evaluated in a swine hemorrhagic shock model to assess its impact on 24-h survival, fluid requirements, and resuscitation time. 20 female pigs were subjected to controlled hemorrhagic shock and randomized into a centhaquine-treated group or a control group receiving only LR solution. Centhaquine significantly reduced the time to reach target MAP (7.10 ± 0.97 vs. 36.88 ± 3.26 min, p < 0.001) and required a lower total fluid volume for resuscitation. Survival at 24 h was 100% with centhaquine and 30% in the control group (p = 0.003). These results suggest that centhaquine enhances survival, accelerates resuscitation, and reduces fluid requirements, making it a promising adjunct for managing hemorrhagic shock	The rapid and efficient increase in MAP with enhanced survivability in the centhaquine-treated hemorrhaged pigs may be attributed to its action as an effective vasopressor, which could enhance tissue perfusion in a condition of lower fluid requirement than control
20	Kontouli et al. [58], 2019	Pig (20)	Resuscitative effect of centhaquine and 6% hydroxyethyl starch 130/0.4  survival in a swine model of hemorrhagic shock	20 Landrace large white pigs were subjected to hemorrhagic shock (MAP decreased to 40–45 mmHg) and randomly assigned to two groups: control (n = 10) and centhaquine group (n = 10). Both groups were given HES 130/0.4 solution for resuscitation until MAP reached 90% of baseline values. During the hemorrhagic phase, the centhaquine group showed a significantly lower HR than controls (97.6 ± 4.4 vs. 128.4 ± 3.6 bpm, p = 0.038). Time to reach target MAP was significantly shorter with centhaquine than in the control group (13.7 ± 0.4 vs. 19.6 ± 0.84 min, p = 0.012). During the resuscitation phase, MAP was significantly higher with centhaquine (89.8 ± 2.1 vs. 75.2 ± 1.6 mmHg, p = 0.02). In the observation phase, significant differences were observed in SVR and CO between the groups (SVR: 1109 ± 32.65 vs. 774.6 ± 21.82 dyn·s/cm5, p = 0.039; CO: 5.82 ± 0.31 vs. 6.9 ± 0.78 L/min, p = 0.027). Survival after 24 h was higher with centhaquine (7/10) than in the control group (2/10, p = 0.008). The centhaquine group also showed significantly lower microvascular capillary permeability and a lower wet/dry weight ratio than the control group (3.08 ± 0.6 vs. 4.8 ± 1.6, p < 0.001). Centhaquine treatment significantly improved hemodynamic parameters, reduced microvascular leakage, and enhanced survival compared with controls, suggesting its effectiveness in hemorrhagic shock resuscitation	The reduced mortality and better resuscitative outcomes in pigs with hemorrhagic shock could be because of improved hemodynamic stability, reduced microvascular leakage, and better CV support after centhaquine administration
21	Ranjan et al. [77], 2021	Rat (15)	Effect of Centhaquine on renal blood flow and tissue protection after hemorrhagic shock and renal ischemia	A rat model of hemorrhagic shock and AKI was used to assess the effects of centhaquine on renal function. After AKI was induced through renal artery clamping and hemorrhage, rats were resuscitated with centhaquine (0.02 mg/kg) for 10 min. Centhaquine significantly improved renal blood flow (p<0.003) compared with the vehicle, despite similar MAP and HR in both groups. Blood lactate levels were lower with centhaquine (p = 0.0064) at 120 min after resuscitation. Histopathological analysis showed reduced renal damage with centhaquine. Western blot analysis revealed higher HIF-1α (p = 0.0152) and lower NGAL (p = 0.01626) levels with centhaquine; immunofluorescence showed increased HIF-1α (p < 0.045) and decreased Bax (p < 0.044) expression. Centhaquine also elevated PHD-3 expression (p < 0.0001) and reduced cytochrome C (p = 0.01429) in the renal cortex. These findings suggest that centhaquine (Lyfaquin®) enhances renal blood flow, promotes hypoxia adaptation, and reduces tissue damage and apoptosis, making it a promising candidate for AKI prevention and treatment	Centhaquine appears to protect kidneys by enhancing perfusion, reducing metabolic distress, and modulating hypoxia and apoptotic pathways after hemorrhage and AKI
22	Gulati et al. [55], 2021	Human (45)	A multicentric, randomized, controlled phase II study to assess the resuscitative effect of centhaquine (Lyfaquin®) in hypovolemic shock patients	50 pts were included; 45 completed the trial: control (n = 22), centhaquine (n = 23). No centhaquine-related AEs during the 28-day observation period. Baseline scores and blood parameters were similar in both groups; however, 91% of the centhaquine group and 68% of the control group required major surgery (p = 0.0526). The 28-day all-cause mortality was 0% with centhaquine and 9% in controls. The centhaquine group spent less time in the ICU and on ventilator support. The total vasopressor requirement in the first 48 h was significantly lower in the centhaquine group (3.12 ± 2.18 vs. 9.39 ± 4.28 mg), and results showed greater increases in SBP and DBP and reduced blood lactate by 1.75 ± 1.07 mmol/l on day 3. Improvements in base deficit, MODS, and ARDS were more pronounced in the centhaquine group. Centhaquine is a safe, well-tolerated, and effective resuscitative agent and improves clinical outcomes in pts with hypovolemic shock	The reduced mortality and improved clinical outcomes in pts with hypovolemic shock could be because of improved hemodynamic stability, reduced vasopressor requirements, and better CV support after centhaquine treatment
23	Gulati et al. [30], 2021	Human (105)	A multicentric, randomized, controlled phase III study to assess the resuscitative effect of centhaquine (Lyfaquin®) in hypovolemic shock patients	This study compared the effects of centhaquine vs. standard care in pts with hypovolemic shock. Both groups received similar amounts of fluids and blood products during the first 48 h of resuscitation, but the centhaquine group required fewer vasopressors. Significant improvements were observed in SBP and PP; centhaquine led to a higher increase in these parameters than in controls, indicating improved SV. The SI was lower in the centhaquine group after 1–4 h of resuscitation. Centhaquine also led to a higher proportion of pts with improved blood lactate and base deficit levels. ARDS and MODS improved, and the centhaquine group had an 8.8% absolute reduction in 28-day all-cause mortality	The reduced mortality and better resuscitative outcomes in pts with hypovolemic shock could be because of improved hemodynamic stability, reduced vasopressor requirements, and better CV support after centhaquine treatment
24	Khanna et al. [78], 2024	Human (12)	Effect of Centhaquine treatment on cardiac output in hypovolemic shock patients	Centhaquine, a resuscitative agent acting on α2B-ARs, was evaluated for its effect on CO in 12 pts with hypovolemic shock. The pilot study found that centhaquine significantly increased SV at 60, 120, and 300 min, and CO was significantly improved at 120 and 300 min despite decreased HR. Increased IVC diameter and LVOT-VTI at these time points indicated enhanced venous return. LVEF and LVFS did not change; MAP rose after 120 and 300 min. Positive correlations between IVC diameter and SV and between IVC diameter and MAP highlighted the role of venous return in improving hemodynamic parameters	Centhaquine’s ability to increase venous return, leading to enhanced SV, CO, and MAP, which are vital for combating circulatory failure and improving outcomes in pts with hypovolemic shock, could be pivotal for its resuscitative effects
25	Chalkias et al. [79], 2024	Rat (27) and Rabbit (59)	Effect of centhaquine on the coagulation cascade using thromboelastography (Teg)	The study evaluated the effects of centhaquine on blood coagulation in both normal and uncontrolled hemorrhage conditions using ex vivo and in vivo experiments. In normal rat blood, centhaquine did not affect TEG parameters or alter the anticoagulant effects of ASA and heparin. In uncontrolled hemorrhage in New Zealand white rabbits, three resuscitation groups were studied: Sal-MAP 45, Centh-MAP 45 (centhaquine + saline), and Sal-MAP 60. Centhaquine increased MA significantly in the Centh-MAP 45 group vs. Sal-MAP 45, without altering other TEG parameters. The Sal-MAP 60 group showed changes indicating impaired coagulation	Overall, centhaquine did not impair coagulation and facilitated hemostatic resuscitation, suggesting its potential benefit in hemorrhage management
26	Gulati et al., 2025	Human (45)	Subgroup analysis of hypovolemic shock patients with significant sepsis	Subgroup analyses of data from phase II (NCT04056065), phase III (NCT04045327), and phase IV (NCT05956418) clinical trials. Efficacy and safety of centhaquine citrate as a resuscitative agent for pts with hypovolemic shock and significant sepsis were assessed. Results demonstrated that centhaquine as an adjuvant to standard of care is safe, well-tolerated, and effective in pts with hypovolemic shock and significant sepsis. Pts treated with centhaquine showed statistically significant improvements in various shock-related endpoints, including reduced vasopressor requirements, better changes in SOFA scores, SBP and DBP, lactate levels, and base deficit than those receiving NS. The centhaquine group also exhibited significant improvements in SOFA score, a key prognostic indicator for sepsis, and required less vasopressor treatment. These findings suggest that centhaquine has the potential to be developed as a new resuscitative agent for septic shock	Centhaquine's beneficial effects in hypovolemic shock with sepsis can be attributed to the improved circulatory stability, reduced requirement for vasopressors, and improvements in SOFA scores

AE adverse event, AKI acute kidney injury, AR adrenoceptor , ARDS acute respiratory distress syndrome, ASA acetylsalicylic acid (aspirin), B_max binding density, BP blood pressure, bpm beats per minute, CO cardiac output, CV cardiovascular, DB double-blind, DBP diastolic blood pressure, DMPP dimethyl phenyl piperazinium iodide, ET_A endothelin A, ET_B endothelin B, h hour(s), HES hydroxyethyl starch, HIF hypoxia-inducible factor, HR heart rate, HS hypertonic saline, IC₅₀ half-maximal inhibitory concentration, ICU intensive care unit, IQR interquartile range, IV intravenous, IVC inferior vena cava, KCl potassium chloride, Kcp intercompartmental transfer rate, Kd binding affinity, Ke elimination coefficient, Kpc reverse intercompartmental transfer rate, LPS lipopolysaccharide, LR lactated ringer’s, LVEF left ventricular ejection fraction, LVFS left ventricular fractional shortening, LVOT-VTI left ventricular outflow tract velocity-time integral, MA maximum amplitude, MAD multiple ascending dose, MAP mean arterial pressure, min minutes, mo months, MODS multiple organ dysfunction syndrome, MTD maximum tolerated dose, n number, NE norepinephrine, NGAL neutrophil gelatinase-associated lipocalin, NS normal saline, PC placebo-controlled, PHD-3 prolyl hydroxylase-3, PP pulse pressure, pts patient(s), SAD single ascending dose, SBP systolic blood pressure, SD Sprague–Dawley, SHR spontaneously hypertensive rats, SI Shock Index, SOFA Sequential Organ Failure Assessment, SV stroke volume, SVR systemic vascular resistance, SW stroke work, TEG thromboelastography, V volume of distribution, Vc central volume of distribution, Vp peripheral volume of distribution, WKY Wistar–Kyoto, 5-HT serotonin.

Hypovolemic Shock: Preclinical Studies

The resuscitative effects of centhaquine have been assessed in various animal models of hemorrhagic and/or hypovolemic shock. Centhaquine dissolved in hypertonic saline augmented resuscitation and increased CO, reduced blood lactate, and increased survival in hemorrhaged rats compared with two control groups receiving saline 0.9% or hypertonic saline [57]. Centhaquine resuscitation also reduced the dependency on norepinephrine to maintain a target mean arterial pressure (MAP) and reduced blood lactate levels (1.65 vs. 4.10 mmol/L) at 1 h after resuscitation in these rats [57]. In another study, rats with hemorrhagic shock dosed with centhaquine had 44% lower blood lactate levels and greater survival rates than control rats [56]. Preclinical testing of centhaquine was also performed in rabbit and pig models of hemorrhagic shock. Results showed that rabbits in the control group needed 207.82 ± 9.08 mL of fluid to maintain the target MAP, whereas rabbits treated with centhaquine needed only 133.60 ± 11.91 mL [80]. Similarly, pigs treated with centhaquine achieved target MAP faster (7.1 vs. 36.9 min), needed lower levels of fluid to maintain target MAP, and had better survival rates (10/10 in the centhaquine group vs. 3/10 in the control group) 24 h after resuscitation than control pigs [63].

The rat model of hemorrhagic shock was also used to explore the signaling pathways involved after resuscitation with centhaquine. Treatment with yohimbine and atipamezole (α2 adrenergic antagonists) significantly reduced the resuscitative effect of centhaquine, indicating that α2-ARs are involved [72]. The involvement of subtypes of α2-ARs was further explored by assessing the antinociceptive activity of centhaquine. All three subtypes of α2-ARs (α2A-, α2B-, and α2C-ARs) are involved in the regulation of nociception [81, 82]. Swiss–Webster mice treated with centhaquine alone or in combination with an antagonist of α2A-ARs (BRL-44408; 2-[(4,5-dihydro-1H-imidazol-2-yl)methyl]-2,3-dihydro-1-methyl-1H-isoindole maleate), α2B-ARs (imiloxan), or α2C-ARs (JP-1302; N-[4-(4-Methyl-1-piperazinyl)phenyl]-9-acridinamine dihydrochloride) were used, and both tail-flick and hot-plate latencies (antinociception) were determined. A significant level of antinociception was produced in mice treated with centhaquine (p < 0.05), which remained unaffected by JP-1302 (p > 0.05) but was antagonized by BRL-44408 (50% decrease in tail-flick test, p < 0.05; 49% decrease in hot-plate test, p < 0.05) and imiloxan (47% decrease in latency in tail-flick test, p < 0.05; 46% decrease in latency in hot-plate test, p < 0.05) [73]. These findings indicate that centhaquine interacts with α2A-ARs and α2B-ARs but not α2C-ARs.

Importantly, studies in animal models of hemorrhagic and/or hypovolemic shock indicated that the mechanism of action of centhaquine involves its predominant interaction with the α2B-ARs and induction of venous constriction, which results in an increased venous return to the heart [73]. By enhancing venous return, it promotes enhancement of CO [57–65]. Centhaquine also acts on the central activation of α2A-AR (Fig. 1) [57–65, 73], which reduces norepinephrine production at nerve endings and hence decreases norepinephrine and α1-AR-mediated arterial constriction, which may improve perfusion at the microcirculatory level by decreasing precapillary arterial tone [83]. Notably, the impact of centhaquine on α2B-ARs, located extrasynaptically, would allow their activation even when α1-AR signaling is diminished after the compensatory phase.

Nevertheless, stimulation of α2-AR and β2-AR by catecholamines has been shown to have prothrombotic effects [84], which may negatively affect hemostatic resuscitation in patients with shock. Both ex vivo and in vivo experiments have been conducted to study the effect of centhaquine on blood coagulation in rats and rabbits in normal and/or uncontrolled hemorrhagic states [79]. Compared with saline, centhaquine did not change the clotting initiation time (R), clotting duration to reach a specific level of firmness (K), speed of fibrin build-up and cross-linking (α), and the strength and firmness of the clot (maximum amplitude [MA]) in blood collected from healthy rats. Centhaquine also did not alter the antithrombotic effects of acetylsalicylic acid (aspirin) and heparin. In the rabbit (in vivo) model of hemorrhagic shock, centhaquine resuscitation to achieve a MAP of 45 mmHg (Centh-MAP 45 group) did not change R, K, and α compared with saline. However, it significantly increased MA [79]. These findings indicate that centhaquine exerts no AEs on blood coagulation under normal and severe hemorrhagic conditions but does increase clot strength during hemorrhage compared with saline, which could be favorable for reducing blood loss after hemorrhage.

Acute kidney injury (AKI) secondary to lack of perfusion and flow is a common consequence of shock. Centhaquine significantly increased renal blood flow, decreased apoptosis, and decreased blood lactate compared with controls [77]. Hypoxia-inducible factor (HIF)-1α plays a crucial role in cellular protection and survival after ischemic/hypoxic injury, whereas an increase in tissue perfusion is known to reduce hypoxia. In this case, kidneys in control rats had less tissue perfusion than centhaquine-treated rats; hence, HIF-1α should have been higher in the kidneys of control rats than in those receiving centhaquine [77]. Surprisingly, HIF-1α was significantly higher in the kidneys of centhaquine-treated rats. Additionally, the expression of prolyl hydroxylase-3 protein, which is regulated by HIF-1α, was higher, indicating an active hypoxia-responsive system and higher oxygenation in the kidneys of centhaquine-treated rats than in control rats [77]. This seemingly paradoxical situation suggests the active and pivotal involvement of mitochondria, lactate clearance, and hypoxia-responsive HIF-1α expression in the presence of centhaquine.

Mitochondrial biogenesis was assessed using in situ polymerase chain reaction with mitochondria-specific gene, MT-ATP8-specific TaqMan probe/primers, and confocal fluorescence microscopy [77]. Mitochondrial biogenesis was higher in the kidneys of centhaquine-treated rats than in controls. Mitochondrial biogenesis is associated with higher mitochondrial function. These findings align with previous research demonstrating the importance of mitochondrial activity in inducing HIF-1α expression in cells exposed to chronic hypoxia [85]. Studies have also highlighted that HIF-1α expression depends not exclusively on oxygen but on factors such as lactate levels, reactive oxygen species, succinate, fumarate, and hydroxyglutarate, indicating the active involvement of mitochondria in the regulation of hypoxia-responsive survival factors [86].

Hypovolemic Shock: Clinical Studies

Phase I was conducted in 25 healthy male volunteers to determine the safety, tolerability, pharmacokinetics, and exploratory pharmacodynamics of centhaquine after a single ascending dose (SAD) and multiple ascending doses (MADs) (Table 3) [65].

Table 3.

Study group treatment details for phase I trials of centhaquine

Study groups	Treatment
Single ascending dose
Cohort I	Centhaquine 0.005 mg/kg (n = 3) or placebo (n = 1)
Cohort II	Centhaquine 0.01 mg/kg (n = 3) or placebo (n = 1)
Cohort III	Centhaquine 0.05 mg/kg (n = 3) or placebo (n = 1)
Cohort IVa	Centhaquine 0.1 mg/kg (n = 3) or placebo (n = 1)
Multiple ascending dose
Cohort V	Centhaquine 0.033 mg/kg (n = 3) or placebo (n = 1) every 8 h for 2 days
Cohort VI	Centhaquine 0.067 mg/kg (n = 3) or placebo (n = 1) every 8 h for 2 days

h hours

^aAn intermediate dose of centhaquine 0.10 mg/kg (n = 3) was used after noticing an adverse event at 0.15 mg/kg (n = 1)

Phases II and III were multicentric, randomized, double-blind, placebo-controlled studies to determine the efficacy and safety of centhaquine in patients with hypovolemic shock [30, 55]. The primary objective of the phase II study was assessment of drug-related AEs for a total period of 28 days; the primary objective of the phase III study was to determine changes (mean through 48 h) in systolic blood pressure (SBP), diastolic blood pressure (DBP), blood lactate levels, and base deficit. The major secondary objectives in both studies included the amount of fluids, blood products, and vasopressors administered in the first 48 h, duration of hospital stay, time in intensive care units, time on ventilator support, change in acute respiratory distress syndrome (ARDS), multiple organ dysfunction syndrome (MODS), and the proportion of patients with 28-day all-cause mortality. In total, 50 patients from seven hospitals in phase II and 105 patients from 14 hospitals in phase III were randomized to centhaquine or control groups [55]. In phase II, patients aged 18–70 years with hypovolemic shock due to blood loss, SBP ≤ 90 mmHg at presentation, and receiving standard care for shock were included [55]. In phase III, patients aged ≥ 18 years, with SBP ≤ 90 mmHg, blood lactate ≥ 2 mmol/L, and receiving standard care for shock were included [30]. The centhaquine group received 0.01 mg/kg in 100 mL saline 0.9% as an intravenous infusion over 1 h, and the control group received an equal volume of saline 0.9% similarly. If SBP dropped below 90 mmHg, a second and/or third dose was administered after 4 h of the previous dose and continued for 2 days after randomization if needed. No more than three doses were administered per day. All patients received standard care for hypovolemic shock, including fluids, blood products, and/or vasopressors [30, 55].

Of 50 patients, 22 and 23 from the control and centhaquine groups, respectively, completed the phase II study, and five patients were excluded [55]. The investigator withdrew three patients after a terminal/systemic illness that was part of the exclusion criteria was detected, and two patients withdrew consent during the study. The average number of doses administered per patient in 48 h was 1.36 ± 0.17 and 1.22 ± 0.11 in the control and centhaquine groups, respectively. At 12 h after resuscitation, SBP increased from baseline in the centhaquine group with a mean difference of 29 mmHg (p < 0.0001). The mean difference in controls was 15 mmHg (p = 0.02) [55]. At 24 h after resuscitation, SBP increased from baseline in the centhaquine group with a mean difference of 33.7 mmHg (p < 0.0001); in the control group, the mean difference was 15.2 mmHg (p = 0.021) [55]. At 48 h after resuscitation, SBP increased in the centhaquine group with a mean difference of 34.1 mmHg from baseline compared with a mean difference of 18.4 mmHg in controls [55]. The centhaquine group required approximately 10.3% less resuscitative fluid doses (saline with or without centhaquine) than the control group in the first 48 h of randomization. A total of 30 doses of saline 0.9% in 22 patients in the control group (1.36 ± 0.17 doses per patient), whereas 28 doses of centhaquine in 23 patients in the centhaquine group (1.22 ± 0.11 doses per patient) were required. Blood lactate was significantly lower in the centhaquine group (p = 0.001) than in the control group (p = 0.44) at day 3. Additionally, the base deficit decreased more in the centhaquine group (− 5.78 ± 1.22 at baseline to 1.33 ± 0.76; p < 0.0001) than in the control group (− 7.40 ± 1.42 at baseline to − 2.58 ± 1.49; p = 0.024) at day 3 [55].

The centhaquine group had a lower MODS score (1.2 ± 0.27) than the control group (3.68 ± 1.45) on day 3. MODS reduced through day 28 in both groups and was lower in the centhaquine group than in the control group [55]. ARDS was assessed using the Murray Score for Acute Lung Injury, which is based on radiological findings, oxygenation status, and ventilation status. A score of 0 indicates no lung injury, and a score > 2.5 indicates ARDS. The centhaquine group had lower ARDS scores than controls on day 2, which continued during the 7-day hospitalization. The ARDS scores improved in both groups through day 28 [55]. The 28-day all-cause mortality was 0% with centhaquine and 9.1% for the control group [55]. All patients in both groups received standard care (fluid + vasopressors + blood products + concomitant therapy) for hypovolemic shock. Fewer patients in the centhaquine group (26.09%) required vasopressors than in the control group (40.91%), and lower volumes of fluid were infused in the centhaquine group (4.26 ± 0.23 L) than in the control group (4.59 ± 0.41 L) [55]. Approximately 86% of patients in both groups received blood products [55].

Of 105 patients, 68 and 34 from the centhaquine and control groups, respectively, completed the phase III study. One patient withdrew consent after enrollment. The investigator withdrew two patients after detecting fulminant tuberculosis in one patient and refractory septic shock in the other after enrollment, so they no longer met the eligibility criteria. Key results are summarized in Table 4 [30].

Table 4.

Results of phase III efficacy endpoints of centhaquine studies

Efficacy endpoints	Time	Percent (number) of patients	p-value
SBP > 90 mmHg	12 h	Centhaquine: 96.9 (63)	0.07
		Control: 87.5 (28)
SBP ≥ 110 mmHg	24 h	Centhaquine: 79.7 (51)	0.04
		Control: 60.6 (20)
SBP ≥ 120 mmHg	48 h	Centhaquine: 56.2 (36)	0.39
		Control: 46.9 (15)
DBP > 65 mmHg	12 h	Centhaquine: 72.3 (47)	0.24
		Control: 60.6 (20)
DBP ≥ 70 mmHg	24 h	Centhaquine: 76.6 (49)	0.01
		Control: 51.5 (17)
DBP ≥ 80 mmHg	48 h	Centhaquine: 50.0 (32)	0.08
		Control: 31.2 (10)
Blood lactate ≤ 1.5 mmol/L	3 d	Centhaquine: 69.3 (43)	0.03
		Control: 46.9 (15)
Base deficit < − 2.0 mmol/L	3 d	Centhaquine: 69.8 (44)	0.01
		Control: 43.7 (14)
Mortality	28 d	Centhaquine: 2.9 (2)	0.07
		Control: 11.8 (4)

d days, DBP diastolic blood pressure, h hours, SBP systolic blood pressure

The shock index, a measure of hemodynamic stability [87], was lower with centhaquine than in the control group at 1 h (p = 0.03) and 4 h of resuscitation (p = 0.05) [30]. Additionally, the Murray Score was reduced in the centhaquine group (p = 0.045) compared with the control group (p = 0.22) at day 3 of resuscitation. MODS from day 3 to day 7 showed a trend toward improvement in the centhaquine group (MODS 1.37 to 0.82, p = 0.11) and toward deterioration in the control group (MODS 1.14 to 1.73) [30].

Although similar amounts of blood products were administered in both groups during 48 h of resuscitation (p = 0.74), the total cumulative dose of vasopressors administered and total volume of fluids infused was lower with centhaquine than in controls: vasopressors: 2.76 ± 1.28 mg, 4.40 ± 2.41 mg, p = 0.55; fluids: 4.61 ± 0.30 L, 4.65 ± 0.37 L, p = 0.92, respectively [30].

Recently, a pilot study [78] was conducted within an ongoing open-label phase IV clinical study (NCT05956418) to evaluate the effect of centhaquine on CO in 12 patients with hypovolemic shock. Patients received intravenous centhaquine 0.01 mg/kg, along with usual resuscitation (e.g., fluids, airway maintenance, and blood products and vasopressors if needed) for hypovolemic shock. None of the patients enrolled in this pilot study needed vasopressors (e.g., inopressors, vasopressin, etc.). Various echocardiography parameters were assessed to determine CO, and blood pressure measurements were carried out at baseline (0 min) and after centhaquine treatment (60 min, 120 min, and 300 min). CO and MAP were increased after centhaquine treatment despite reduced heart rate and unchanged total peripheral/systemic vascular resistance, indicating the effect of centhaquine on increased circulation and blood pressure [78]. Since improved CO is known to promote tissue perfusion, the factors associated with tissue perfusion were assessed, such as the partial pressure of oxygen in arterial blood (PaO₂)/fraction of inspired oxygen (FiO₂) ratio (P/F ratio), blood lactate level, and urine output. A significant increase from baseline to 24 h in P/F ratio (376.7 ± 6.3 to 405.5 ± 1.7; p = 0.0002) and decrease in blood lactate level (2.5 ± 0.06 to 2.0 ± 0.03 mmol/L; p < 0.0001) were observed (Fig. 2A, B). A correlation (R² = 0.49; p = 0.011) between increased CO and the P/F ratio was observed (Fig. 2C), but a correlation between CO and decreased lactate level was not (R² = 0.03; p = 0.011) (Fig. 2D). No significant change in urine output was seen [78].

Fig. 2.

Effect of centhaquine on tissue perfusion. The tissue perfusion indicators A partial pressure of oxygen in arterial blood (PaO₂)/fraction of inspired oxygen (FiO₂) ratio (P/F ratio) and B blood lactate are significantly improved in patients after 1 day of centhaquine treatment. The P/F ratio was correlated with an increase in C cardiac output, whereas D lactate level was not significantly correlated with CO, measured at 300 min after centhaquine treatment [86].

After centhaquine treatment, the increased P/F ratio in patients and its correlation with increased CO may reflect better tissue perfusion due to increased CO. In addition, since no patients needed vasopressor administration, the reduced blood lactate level was probably mechanistically related to increased tissue perfusion and lack of microcirculatory compromise after centhaquine treatment. However, further studies are required to provide direct evidence for better tissue perfusion after centhaquine treatment in patients with shock.

Septic Shock Studies

The effect of centhaquine 0.05 mg/kg on survival and hemodynamic performance was evaluated in a rat model of septic shock induced by intravenous lipopolysaccharide 20 mg/kg [74]. Although centhaquine significantly increased heart rate and CO and showed a trend toward increased stroke volume compared with in the control group, it did not improve survival time. Its temporary enhancement of cardiac performance may be attributed to the modulation of vascular tone and adrenergic signaling, but it might not mitigate the systemic inflammatory response or multiorgan dysfunction of severe sepsis. However, recent subgroup analyses of data from phase II (NCT04056065), phase III (NCT04045327), and phase IV (NCT05956418) clinical trials in patients with hypovolemic shock and significant sepsis indicated that centhaquine, when used as an adjuvant to standard care, is safe, well-tolerated, and effective in patients with hypovolemic shock and sepsis. It significantly improved shock-related endpoints, including reduced vasopressor requirements, better Sequential Organ Failure Assessment scores, and improved hemodynamic parameters (in-house unpublished data, Gulati et al., 2025). These findings suggest that centhaquine has potential as a novel resuscitative agent for septic shock; however, further preclinical and clinical septic shock studies are required.

Pharmacokinetics

The pharmacokinetics of centhaquine were evaluated preclinically in rat and dog models and in healthy human volunteers in the phase I study. Animal studies indicated a short half-life and large volume of distribution [61, 62]. An intravenous bolus dose of 0.45 mg/kg was administered in rats and 1.0 mg/kg in dogs. Pharmacokinetic parameters are given in Table 5.

Table 5.

Pharmacokinetic properties of centhaquine in rats and dogs [61, 62]

Pharmacokinetic parameters	Rat	Dog
AUC (ng/mL/h)	3.0 (1.6–4.1)	8.7 (8.6–9.1)
AUC0–inf (ng/mL/h)	3.0 (1.6–4.1)	8.7 (8.6–9.1)
Cmax (ng/mL)	14.8 (6.8–27.8)	34.3 (31.6–38.0)
tmax (h)	0.017 (0.017–0.017)	0.017 (0.017–0.017)
Cl (L/h)	35.2 (26.2–68.7)	1542 (1392–1662)
Vdss (L)	17.6 (13.0–31.0)	1414 (1331–1484)
t½ (h)	0.55 (0.26–0.94)	0.81 (0.79–0.82)

Data are presented as median (interquartile range)

AUC area under the plasma concentration-time curve, Cl clearance, C_max maximum plasma drug concentration, t_max time to C_max, t_½ elimination half-life, Vdss volume of distribution at steady state

Pharmacokinetics were analyzed in phase I for SAD and MAD cohorts. For SAD, the maximum plasma concentration (C_max) was approximately 0.6–30.6 ng/mL, the time to reach C_max was 5–10 min, the elimination half-life was 43–97 min, and the elimination rate constant was approximately 1–0.4 [65]. For a MAD of 0.03 mg/kg, a C_max of approximately 9 and 8 ng/mL was achieved within 5 min of the first and last dose, respectively. For a MAD of 0.07 mg/kg, a C_max of 10.5 and 13 ng/mL were achieved within 5 min of the first and last dose, respectively [65].

In the pilot study conducted in 12 patients with hypovolemic shock, centhaquine treatment normalized the heart rate, respiratory rate, and body temperature, decreased the levels of blood lactate and base deficit, and increased the P/F ratio. Patient outcomes were improved, with decreased MODS and stabilized hematologic, biochemical, and serum electrolyte levels. No AEs were reported in any patients, and all patients recovered and were discharged at 3.1 ± 0.07 days. Thus, the efficacy and safety of centhaquine in patients with hypovolemic shock patients was promising [78].

Safety Data

In phase I, five non-serious AEs in two subjects were mild and reversible and resolved quickly without sequelae/intervention: hypotension and lactic acidosis in one subject (0.15 mg/kg) and decreased respiratory rate, dry mouth, and drowsiness in another subject (0.10 mg/kg) [65]. Safety analysis found centhaquine to be well-tolerated and safe when administered as a SAD and with MADs. The maximum tolerated dose was 0.1 mg/kg, ten-fold higher than the therapeutic dose [75].

Two AEs were reported in centhaquine-treated patients during phase II, including diarrhea and AKI, which were moderate in severity, resolved with treatment, and unrelated to centhaquine [55]. In phase III, five AEs were reported in five patients receiving centhaquine, including increased serum creatinine levels (moderate severity) in two patients and vomiting (mild severity) in one patient. The other two patients died. All AEs were determined to be completely associated with disease progression and not related to the study drug.

Limitations of Current Evidence

Although centhaquine has demonstrated promising resuscitative effects in patients with hypovolemic shock, with increased patient outcomes and survival rates in clinical trials, further larger and long-term trials are required to ensure the efficacy, safety, and overall suitability of the drug for clinical use. The completed trials involved small sample sizes (n = 50 and n = 105 in the phase II and III studies, respectively). Further confirmation of its efficacy and robust statistical evidence are required in more extensive and well-powered trials. All completed trials were conducted in Indian patients with hypovolemic shock, the efficacy of the drug must be validated in different demographic groups and clinical settings. New trials in various countries are imperative to ensure that the findings apply globally and not just to specific regions with specific healthcare systems. Global trials will also standardize treatment across different trial sites, reduce variability, and improve the generalizability of the outcomes. The observation periods in the trials were short (maximum 28 days), so the long-term safety and chronic effects of centhaquine are yet to be determined. Ultimately, real-world evidence will provide insights into how centhaquine performs in everyday clinical practice.

Conclusions

Selective α2B-AR agonists that promote venous return and enhance tissue perfusion may mitigate shock-induced organ damage and possibly mortality. However, further research into the precise mechanisms of action and the clinical implications is crucial for a comprehensive understanding of the therapeutic potential in various types of shock and other hypoxia-related conditions.

Declarations

Funding

Open access funding provided by the Carolinas Consortium.

Conflict of interest

AR is employed by and SR was previously employed by Pharmazz Inc., Willowbrook, IL, USA, the manufacturer of centhaquine citrate. AG is employed by Pharmazz, Inc. and has issued and pending patents related to the studies described in this review. AKK consults for Pharmazz Inc., Medtronic, Edwards Life Sciences, Trevenna Pharmaceuticals, Philips Research North America, GE Healthcare, Potrero Medical, Retia Medical, and Caretaker Medical and has previously consulted for La Jolla Pharmaceuticals; his previous institution received grant funding from La Jolla Pharmaceuticals for the Angiotensin II in High Output Shock Trial. DB consults for Pharmazz Inc., Viatris, AOP Pharma, Edwards Life Sciences, and Philips. MO has received research funding from Baxter and bioMérieux. ML is supported by grant R01-GM151494-01 and R01DK139484-01 from the National Institutes of Health. All other authors have declared "No Conflict of Interest". 

Ethics approval

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Code availability

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Availability of data and materials

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Author contributions

Conceptualization and design: ML, AKK, AG, DB, MO, JV, AR, and SR. Visualization: ML. Writing – original draft: AKR, ML, SR, and DB. Writing – review and editing: AR, ML, DB, AG, MO, JV, SR, and AKK. All authors have read, agreed, and approved the final manuscript.