Herb drug interaction: effect of Manix® on pharmacokinetic parameters of pefloxacin in rat model

Abstract

Objective

To evaluate the effect of Manix®, the commonly used polyherbal formulation on pefloxacin pharmacokinetic parameters.

Methods

Microbiological assay was employed using clinical isolate of Escherichia coli samples from hospitalized patients.

Results

Manix® altered the bioavailability parameters of pefloxacin as thus, maximal concentration (C_max) of pefloxacin (0.91±0.31) µg/mL occurred at time to reach maximal concentration (t_max) 4.0 h while in the group that received Manix® alongside pefloxacin C_max was (0.22±0.08) µg/mL at t_max 1.0 h respectively. The area under curve of pefloxacin alone was (7.83±5.14) µg/h/mL while with Manix® was (2.60±0.08) µg/h/mL. There was a significant difference between C_max, t_max and area under curve between pefloxacin alone and pefloxacin after Manix® pre-treatment (P<0.05).

Conclusions

The concurrent use of Manix® and pefloxacin has been found to compromise the therapeutic effectiveness of pefloxacin which could lead to poor clinical outcomes in patients.

1. Introduction

Infertility is a medical problem that affects more than 80 million people worldwide and it is one of the indicators of poor reproductive health. It affects about 15% of global young adults' population. It is a threat to humans continued survival on earth[1]. In sub-Saharan Africa, the male factor infertility is on the increase. In easthern and southern parts of Nigeria, the oligospermia and azoospermia have been identified as the common causes of male factor infertility, which are attributable partly to bacterial infections[2]. Seminal fluid infection has been implicated to contribute tremendously in the reduction of sperm density and cause abnormal sperm morphology. According to WHO, infection should be suspected in sperm pH changes and Nwakyoma et al. in their study stated that pH changes affect most of the seminal fluid parameters and that these contribute to the problem of infertility[3]. Meanwhile, Staphylococcus aureus, Streptococcus and Escherichia coli (E. coli) are among other causative microbes named both in Nigeria and other parts of the globe[2]. The presence of DNA from sexually transmitted disease pathogens detected in semen of asymptomatic men seeking an infertility investigation is a further proof of microbes' involvement in male factor infertility[1]. In reality, infertility is a multifactorial condition with more than one factor contributing to elicit the disease. The factors include psychological, emotional disorders, alcohol and drugs addiction that cause infertility in form of loss of libido, rapid ejaculation or erectile dysfunction. Some lifestyle and organic diseases such as smoking, obesity, diabetes, hypertension, cardiovascular and neurological disorders have been implicated to cause male infertility that manifest in form of oligospermia or azoospermia[4].

Male factor infertility due to infections is often reversible. Most people who had acute epididymitis experienced temporary impairment of spermatogenesis that can be reversed with potent antibiotic therapy to normalcy[2]. Pefloxacin is a synthetic antimicrobial agent. It is the third generation of fluoroquinolones with a broad spectrum of activity against most Gram-negative and Gram-positive bacteria. Fluoroquinolones including ciprofloxacin and nalidixic acids can be used successfully in a variety of specific infections like urinary tract infections (UTIs)[5],[6]. Pefloxacin has a good absorption with high bioavailability, a long half-life, excellent tissue and body fluid penetration[5],[7].

Infertility in males manifests as poor libido, low sperm count or poor sperm quality that necessitates the use of polyherbal formulation like Manix®[8]. This polyherbal formulation is commonly prescribed for Nigerian males with low sperm count and poor sperm quality by physicians. It has been established that Manix® reverses the age related decrease in testosterone levels in males to as much as 85% when taken for 90 d. It also increases by 41% and improves sperm motility by 124%, and increases the sperm count four times in 90 d[8],[9]. Each Manix® capsule contains extract (Manix® Product leaflet) of Asparagus racemosus, Tribulus terrestris, Tinospora cordifolia, Semecarpus anacardium, Pueraria tuberose, Plumbago zeylanica, Cinnamomum zeylanicum, Elettaria cardamomum, Cinnamomum tamala, Dioscorea bulbifera and Sesamum indicum.

Manix® is commonly prescribed for Nigerian males with low sperm count by physicians and in some cases with pefloxacin especially when there is UTI comorbidity. This research was designed to investigate the effect of this polyherbal formulation, Manix®, on the pharmacokinetic parameters of pefloxacin.

2. Materials and methods

2.1. Drugs

Pure sample of pefloxacin (Evans Ltd., Nigeria), MacConky agar (Zayo-Sigma Ltd., Nigeria), Nutrient agar (Zayo-Sigma-Aldrich), pefloxacin tablets branded Peflacine® having label strength of 400 mg and Manix® were purchased from a registered retail pharmacy in Nsukka, Enugu State, Nigeria.

2.2. Animals

Ten rats of both sexes, with a mean body weight of (135.4±9.0) g, were used in this study after being left in two cages (same sex to one cage) for seven days to make them acclimatize to the laboratory environment. The rats had access to food and water ad libitum. The rats' serum samples were collected prior to the experiment and tested for the presence of antimicrobial agent using microbiological assay method to rule out pre-clinical antimicrobial effects of the animals' feed.

2.3. Study design

After an overnight fasting period of 8 h on the eighth day, the rats were randomly devided into two groups of five rats per group. A group was administered pefloxacin (5.7 mg/kg) alone, while the other group was treated with Manix® for ten days and on Day 11 was dosed with pefloxacin (5.7mg/kg) orally.

2.4. Sample collection

Blood samples (about 5 mL per rat per time) were collected from tail veins of the rats at 0 h, 0.5 h, 1 h, 4 h, 8 h and 24 h, after pefloxacin administration in both groups in heparinized containers, and being centrifuged at 3 000 r/min for 10 min. The serums collected were used for microbiological assay.

2.5. Drug analysis

Microbiological assay was employed using clinically isolated E. coli samples from hospitalized patients to determine the serum concentrations of pefloxacin[5]. The nutrient agar was supplemented with 0.1% KH₂PO₄, then cooled to 50 °C and inoculated with 24-h incubated E. coli culture (0.1 mL/100 mL agar). After the solidification holes of 10 mm were punched out of the agar. Subsequently the punch-holes were filled with 100 µL of serum in duplicate for calibrators and samples. After the incubation at 37 °C (about 18 h), the inhibition zones were measured and the concentrations were calculated.

2.6. Pharmacokinetic analysis

Selected pharmacokinetic parameters of pefloxacin alone and pefloxacin with Manix® were determined using WiNonlin noncompartmental programme as follows: half-life (t_1/2), apparent volume of distribution (V_d), area under the serum concentration-time curve (AUC_0-24h), mean residence time (MRT) and clearance body (Cl), peak serum concentration (C_max), time to reach C_max (t_max). The relative bioavailability of pefloxacin after co-administration with Manix® was calculated by dividing the AUC after being combined administration by the AUC after single administration. Statistical analysis was performed using nonparametric (Mann-Whitney) two sample tests.

3. Results

The pharmacokinetic parameters of pefloxacin when being administered alone and following Manix® pretreatment are shown in Table 1 and the concentration-time graph are shown in Figure 1. In the presence of Manix® the bioavailability parameters of pefloxacin were as follows: C_max of pefloxacin (0.91±0.31) µg/mL occurred at t_max 4.0 h while in the group that received Manix® alongside pefloxacin C_max was (0.22±0.08) µg/mL at t_max 1.0 h respectively. The AUC of pefloxacin alone was (7.83±5.14) µg/h/mL while with Manix® was (2.60±0.08) µg/h/mL.

Table 1. The pharmacokinetic parameters of pefloxacin on co-administration with polyherbal formulation (Manix®) using microbiological assay.

Parameter	Pef alone	Pef+Manix® (E. coli)
Tmax (h)	4.0	1.0*
Cmax (µg/mL)	0.91±0.31	0.22±0.09*
Clast (µg/mL)	0.11±0.03	0.06±0.01
AUC (µg/h/mL)	7.83±5.14	2.60±0.08*
t1/2 (h)	10.79±1.81	13.86±4.86*
Vd (mL)	1.10±0.01	3.51±0.80*
Cl (mL/kg/hr)	0.07±0.01	0.18±0.02*
AUMC (µg/mL/h2)	57.65±8.89	22.67±5.04
MRT (h)	7.36±2.35	8.70±0.00

*: Significance difference between pefloxacin alone and pefloxacin after Manix® pretreatment at P<0.05.

Pef: Pefloxacin; T_max: Time taken for drugs to attain maximal plasma concentration; C_max: Maximal drug plasma concentration; Clast: Last measurable drug plasma concentration; AUC: Area under curve from the time of dosing to the time of the last observation; AUMC: Area under moment curve from the time of dosing to the time of last measurable concentration; MRT: Means residence time; t_1/2: Terminal half-life: V_d: Volume of distribution based on the terminal phase; Cl: Total body clearance.

Figure 1. Effect of Manix® on plasma concentration of pefloxacin (Pef).

This difference in C_max, t_max and AUC between pefloxacin alone and pefloxacin after Manix® pre-treatment were significant (P<0.05). In the same way, the area under first moment curve (AUMC) in pefloxacin alone and after Manix® pretreatment were (57.65±8.89) µg/mL/h² and (22.67±5.04) µg/mL/h² respectively.

While the pharmacokinetic parameters of pefloxacin were as follows: half-life for pefloxacin alone and pefloxacin after Manix® pretreatment were (10.79±1.81) h and (13.86±4.86) h respectively (P<0.05), the V_d of pefloxacin treated animal was (1.10±0.01) mL while in animals pretreated with Manix® the pefloxacin V_d was (3.51±0.80) mL (P<0.05). The total body clearance of pefoxacin alone and pefloxacin after Manix® pretreatment were (0.07±0.01) mL/kg/h and (0.18±0.02) mL/kg/h respectively.

4. Discussion

Pefloxacin has good antimicrobial spectrum against Gram positive and Gram negative microorganisms and has been successfully used in the treatment of both human and animal diseases. Pefloxacin is partially metabolized in the liver to norfloxacin, which is a potent antimicrobial agent[7]. Due to its favourable pharmacokinetic properties such as good bioavailability, better volume of distribution and minimal chances of resistance, it is one of the favoured antibacterial agents for treatment of bacterial infectious diseases particularly in reproductive health.

Bioavailability is the measurement of the rate and extent of systemic availability of a drug. Therefore, the AUC, the C_max that indicates the amount of drug reaching the systemic circulation (extent) and time to reach maximal concentration (T_max) that indicates time taken to reach the systemic circulation (rate) are used as measures for assessing bioavailability[10]. Manix® significantly decreased both the AUC and C_max of perfloxacin and also decreased the time to attain C_max of perfloxacin in the Manix® pre-treated group. The decreased AUC and C_max were indicative of fewer drug reaching systemic circulation in the Manix® treated group hence reduced availability of perfloxacin. This significant decrease in AUC and C_max may lead to a decrease in effective concentration of perfloxacin in the plasma which may lead to subtherapeutic level of the drug with its resultant treatment failure and the risk of development of microbial resistance.

Most herbs have poorly absorbable hydrocolloidal carbohydrates that readily bind to drugs when consumed in their natural powdered form[11]; Manix®, which has many natural product constituents, is a candidate herbal product likely rich in these class of carbohydrates hence was able to cause significant decrease in AUC and C_max of pefloxacin when co-administered.

However, the decreased AUC and C_max may also be due to enhanced tissue penetration of pefloxacin in the presence of manix® which may limit its concentration at the plasma at the moment of blood withdrawal. Fluoroquinones have been shown to have rapid and extensive tissue distribution due to their hydrophilic nature and they attain high intracellular concentrations in macrophages and neutrophils and their intracellular concentrations are also shown to be 4-10 times greater than plasma concentrations[12]. The possible better intracellular concentration of the drug in the presence of manix® is further indicated by the significant higher volume of distribution value obtained in the pre-treated group which is also indicative of a better penetration of the drug into various body tissues[13].

The reduced bioavailability of perfloxacin in the manix® pre-treated group may be due to activation of drug transport mechanism by one or more of the manix® constituents thus decreasing absorption and/or due to induction of drug metabolising enzymes leading to enhanced perfloxacin metabolism and subsequently decreased systemic availability. Perfloxacin has been shown to be metabolised in the liver and also bio-transformed through cytochrome P450 1A2 enzymes and therefore, enzyme induction by Manix® will lead to enhanced drug metabolism and also possibly enhanced the biotransformation of perfloxacin. These will likely result in decrease in plasma perfloxacin concentration in the manix® pre-treated group.

Meanwhile, there was significant increase in half life, mean resident time and clearance of perfloxacin in the Manix® pre-treated group which is not in line with the suggested possible induction of metabolising enzymes by Manix®. This observation may be due to the fact that perfloxacin is actively transformed with its principal metabolite being norfloxacin which is also very active metabolite[14]. Since microbiological assay method was used in this study, the effect of the norfloxacin may be involved in the prolongation of t_1/2, Cl and MRT.

Furthermore, the result showed a significant increase in the volume of perfloxacin distribution in the Manix® pretreated group. This may probably be due to enhanced effect of Manix® on the protein binding capacity of the drug. Pefloxacin is only 20% to 30% (<50%) protein bound[12]. A decrease in plasma protein binding will result in an increase in the volume of distribution and thus, a prolongation of the elimination half life and mean resident time. Finally, the increased clearance may be due to the presumed decreased effect on plasma protein binding leading to more drug presentation to the enzyme effect and hence, increased metabolism and clearance.

A drug useful in the management of reproductive system infections should not have the therapeutic effectiveness compromised through herbal formulation co-administration. Our study shows that the concurrent use of Manix® and pefloxacin has been found to compromise the therapeutic effectiveness of pefloxacin thus may lead to poor clinical outcomes in patients. It is therefore advisable that patients on pefloxacin should not be placed concurrently on this polyherbal formulation to avoid therapy failures.

Comments

Background

This is a good study in which the authors evaluated pharmacokinetic parameters of perfloxacin in polyherbal combinations therapy in a mice model. The results are good despite being faced with some limitations. This study could serve as a baseline study.

Research frontiers

This study involved an evaluation of the effects of the commonly used polyherbal formulation on perfloxacin pharmacokinetic parameters. Pharmacokinetic of herbal concoctions is usually limited due to unknown compounds that not yet elucidated.

Related reports

Some of the listed herbal plants have shown to have antimicrobial activity. However, antimicrobial evaluation technique was not mentioned here.

Applications

From previous studies, it has been shown that drugs can antagonize each other or get synergized in combination therapy. However, this effect has not yet been evaluated on herbal concoctions without elucidated compounds despite the limitations or working with unknown compounds.

Peer review

It is a valuable study and it shows the impact of herbal drugs on conventional drugs when given as a combination therapy. This study was based on bioavailability parameters when given concurrently. Manix® was found to compromise the therapeutic effectiveness of perfloxacin.