Pilot study of peak plasma concentration after high-dose oral montelukast in children with acute asthma exacerbations

Abstract

Acute asthma exacerbations are primarily due to airway inflammation and remain one of the most frequent reasons for childhood hospitalizations. While systemic corticosteroids (CCS) remain the mainstay of therapy due to their anti-inflammatory properties, not all inflammatory pathways are responsive to CCS, necessitating hospital admission for further management. Cysteinyl leukotrienes (LTs) are proinflammatory mediators that play an important role in CCS non-responsiveness. Montelukast is a potent LT-receptor antagonist, and an intravenous (IV) preparation caused rapid, sustained improvement of acute asthma exacerbations in adults. We hypothesized that a 30 mg dose of oral montelukast achieves peak plasma concentrations (C_max) comparable to the IV preparation (1,700 ng/ml) and would be well tolerated in fifteen children aged 5 – 12 years with acute asthma exacerbations. After administration of montelukast chewable tablets, blood samples were collected at 0, 15, 30, 45, 60, 120, 180, and 240 minutes. Plasma was separated and frozen at –80° C until analysis for montelukast concentration using liquid chromatography, tandem mass spectrometry. Median time to C_max (t_max) was 3.0 hours. Six participants (40%) achieved C_max of 1,700 ng/ml or higher. However, there was high inter-individual variability in peak plasma concentration (median C_max of 1378 ng/ml; range 16 – 4895 ng/ml). No participant had side effects or adverse events. Plasma concentrations from this pilot study support the design of a weight-based, dose-finding study aimed at selecting an optimal dose for future clinical trials to assess the efficacy of high-dose oral montelukast in children with moderate to severe asthma exacerbations.

Introduction

Children with acute asthma exacerbations have a high hospitalization rate (median 24%, range 13 – 50%) from U.S. children’s hospital emergency departments (EDs).^1–3 Hospitalization is needed most often because some airway inflammatory pathways are non-responsive to systemic corticosteroid (CCS),^4–6 a mainstay treatment and the only anti-inflammatory medication available for exacerbations since 1956.⁷ NIH expert guidelines recommend that clinicians make the decision for hospitalization within 4 hours of CCS treatment, an interval during which any CCS-induced improvement in lung function is expected.^8,9

Cysteinyl leukotrienes (LTs), inflammatory mediators synthesized by airway mast cells and eosinophils, are an important cause of CCS non-responsiveness.^10–15 LT synthesis is induced by viral respiratory infections^16–21 and aeroallergens,^22,23 the most common asthma triggers in children.^10,24 Though some inflammatory pathways induced by these triggers are CCS-responsive, LT-mediated airway inflammation is CCS non-responsive.²⁵

Montelukast sodium is a potent LT-receptor antagonist (LTRA). It is approved as an oral controller medication for chronic asthma and allergic rhinitis in children and adults but is not FDA approved for asthma exacerbations.²⁶ Randomized controlled trials of intravenous (IV) montelukast for moderate and severe exacerbations in adults demonstrated rapid and sustained improvement of lung function measured by forced expiratory volume in 1-second (FEV₁), and doses of 7 mg or 14 mg IV had equivalent efficacy.^27–29 A dose of 9 mg IV achieved peak plasma concentration (C_max) of approximately 1,700 ng/mL in adults, a concentration above which therapeutic benefit may be anticipated, based on these clinical trials.³⁰ However, because the IV preparation is not available, clinical trials of “high-dose” oral montelukast may be considered.

Montelukast is water-soluble, largely bound to plasma proteins, 60–70% bioavailable, and has linear disposition kinetics.³¹ For the 5 mg montelukast chewable tablet, potency-normalized C_max was 495 (SD 129) ng/ml and time to C_max (t_max) 2.6 + 1.0 hours.³² In addition, we have reported that single doses of oral montelukast >50 mg and up to 17.8 mg/kg body weight are rarely associated with side effects in children, the most common of which are abdominal pain, vomiting, dizziness and headache that each occur in <1.5%.^33,34

The objective of this research was to determine the plasma concentration profile, including C_max and t_max, of single 30 mg “high-dose” chewable montelukast in children with acute asthma exacerbations presenting to a tertiary, urban children’s hospital emergency department. Based on the data above, we hypothesized that this dose would result in C_max approaching 1,700 ng/ml and would be well-tolerated.

Methods

This research was reviewed and approved by the Vanderbilt University institutional review board (protocol #182070). The U.S. Food and Drug Administration (FDA) granted an active Investigational New Drug (IND) authorization for the montelukast dose used in this research (IND #136451). Each participant and their parent provided informed written consent. The research was conducted at the Monroe Carell Jr., Children’s Hospital ED, Vanderbilt University Medical Center, Nashville, TN.

Study Design and Participants

We performed a prospective observational study in a convenience sample of 15 children aged 5 – 12 years with doctor-diagnosed asthma who presented to our tertiary, urban children’s hospital ED with acute asthma exacerbations. Exclusion criteria included prior study enrollment; chronic lung disease other than asthma; history of prematurity less than 34 weeks gestational age; acute or chronic liver disease; presence of tracheostomy; use of noninvasive ventilation at home; need for immediate airway intervention (e.g., endotracheal intubation or noninvasive ventilation); allergy to montelukast; and female with any evidence of Tanner stage 2 (breast budding) or greater breast development because pregnancy testing was not performed.

The Vanderbilt Investigational Drug Service (IDS) prepared montelukast 5 mg chewable tablets (BionPharma, NDC 69452–107-19) in sealed packets, each containing 6 tablets (total dose 30 mg). IDS created study drug files that linked to an automated drug dispensing cabinet (Omnicell®, Mountain View, CA) in the ED. Bar-coded labels were applied to the drug packets and were scanned when the nursing staff dispensed the drug to the investigators. Drug packets were inventoried in a pocket inside the cabinet specifically designated for this study.

We called each participant’s parent 24–48 hours after study enrollment at the phone number provided at the time of enrollment. The parent was queried about drug tolerability, side effects and any concerns the parent had regarding montelukast or the research protocol. Participants were provided financial compensation for their time and effort.

Sample Acquisition and Preparation

Once a patient-parent dyad provided informed, written consent and assent, study drug was dispensed and an intravenous (IV) catheter placed. The participant was asked to chew and swallow the 6 montelukast chewable tablets followed by 60 ml tap water to promote drug dissolution. Whole blood samples were drawn through the IV catheter before drug administration (time 0) and again at approximately 15, 30, 45, 60, 120, 180 and 240 minutes. Room lighting was minimized during blood draws because montelukast is light sensitive. Each sample was immediately transferred to a 4 ml venous blood collection tube containing heparin anticoagulant (McKesson Medical-Surgical, Richmond, VA) and covered with aluminum foil to minimize light contamination. Samples were transported to a lab within the ED and processed with ambient lighting minimized. Each blood collection tube was immediately centrifuged at 2500 rpm for 15 minutes and plasma transferred by pipette to light resistant cryovials. Cryovials were placed on ice and transferred to storage at –80° C until quantitative analysis. The average time to patient sample analysis was 46.2 days. Previous research has reported that montelukast is stable for at least 19 months in human plasma at −70° C, and repeated freezing and thawing of samples three times had no apparent adverse effects on stability.³⁵

Sample Processing and Extraction

A six-point standard curve for montelukast ranging from 5 – 5000 ng/ml along with at least three concentrations of quality controls (15, 150, 300, 1500, 3000 ng/ml) were utilized to quantitate montelukast concentrations in plasma. Standards and controls were prepared by spiking blank human plasma with an appropriate amount of montelukast stock solution (1 mg/ml in methanol) stored at −20°C.

Prior to each analytical run, standards were prepared fresh while quality control and participant samples were thawed on ice. For each sample, 100 μL of standard, control, and participant sample were transferred to a 96-well plate containing 400 μL of ice-cold acetonitrile spiked with montelukast-d6 (internal standard; 100 ng/ml). Samples were vortexed for 3 min and subsequently centrifuged for 5 min at 3000. The supernatant was transferred to a new 96-well plate, dried under a stream of nitrogen (40°C), and reconstituted in 100 μL of mobile phase prior to liquid chromatography, tandem mass spectrometry (LC-MS/MS) analysis.

Analytical Method and Montelukast Quantitation

Quantitation of montelukast plasma concentrations in standards, quality controls, and participant samples was achieved by LC-MS/MS analysis. Samples were loaded into a CTC Analytics PAL-xt DW Autosampler and 5 μL was injected into a Shimadzu LC-20 AD Series HPLC System coupled to a Sciex 6500 QTrap mass spectrometer (Foster City, CA). Compounds were separated on a C-18 column (50 × 2.1 mm, 1.7 μm, Phenomenex, Torrance, CA) heated to 60°C using a 90:10 (v/v) mobile phase mixture of 0.1% formic acid in water (mobile phase A) and 0.1% formic acid in acetonitrile (mobile phase B) at a flow rate of 0.5 mL/min. The gradient for mobile phase B was increased from 10 to 90% over 1.5 minutes with a total run time of 2 minutes. Detection of montelukast and montelukast-d6 was carried out by LC-MS/MS analysis with electrospray ionization set in the positive ion mode followed by multiple-reaction monitoring of precursor and product ions for montelukast (m/z 586.2 to 422.2) and montelukast-d6 (m/z 592.2 to 574.2).

All montelukast standards and quality control samples met the following acceptance criteria: (1) standard curve of at least 5 standards each within 15% of the nominal concentration and an R² > 0.90; (2) 66.7% of all QC samples and at least 50% at each QC concentration (low, medium, and high) were within 15% of the nominal concentration. LLOQ control samples were required to be within 20% of the nominal concentration. Participant samples with montelukast plasma concentrations that exceeded the high end of the standard curve were diluted 1:10 with blank human serum, re-calculated using a dilution factor of 10, and were accepted as a final result if the corresponding diluted QC (10,000 ng/ml) met the above QC criteria. The lower limit of quantitation control (LLOQ) for the assay was 5 ng/ml with an accuracy and precision of < 9%. Intra-day and inter-day precision for the assay was < 16% and < 10%, respectively. Intra-day and inter-day accuracy for the assay was < 8% and < 9%, respectively.

Data Management

Data were recorded at the bedside and during follow-up phone calls with parent using a standardized data-collection form. Study data were inventoried and managed using Research Electronic Data Capture (REDCap) electronic data capture tools hosted at Vanderbilt University Medical Center.^36,37 REDCap is a secure, web-based software platform designed to support data capture for research studies, providing 1) an intuitive interface for validated data capture; 2) audit trails for tracking data manipulation and export procedures; 3) automated export procedures for seamless data downloads to common statistical packages; and 4) procedures for data integration and interoperability with external sources. Data entry accuracy was ascertained by two investigators (DHA, WSA). REDCap data were exported directly to the statistical software for analysis.

Data Analysis

Individual montelukast concentrations at each time point were imported into Phoenix WinNonlin® 8.0 software (Certara USA, Inc., Princeton, NJ) to generate a plasma concentration-time profile for each participant. Noncompartmental analysis using Model 200 (Plasma; Single Extravascular Dose; Linear Log Trapezoidal Method) was performed on each plasma concentration-time profile to estimate C_max, t_max, and the area under the concentration-time curve from zero to the last time point collected (AUC_last). Montelukast C_max values for each participant were evaluated using box and whisker plots to determine the mean, median and the interquartile range of peak drug exposure and the percentage of participants who achieved a target threshold of 1700 ng/ml.

Results

Participant demographic and asthma characteristics are displayed in Table 1. Participants had median [interquartile range, IQR] age 8.8 [6.5, 11.2] years, with the majority male and African-American. Most participants were currently using inhaled albuterol and had food intake within 13 hours (median 2 [0.5, 6]).

Table 1.

Demographic and asthma characteristics of 15 children aged 5 – 12 years with acute asthma exacerbations who received montelukast chewables (30 mg)

Characteristic	Value
Age, years, median [IQR]	8.8 [6.5, 11.2]
Weight, kg, median [IQR]	35.8 [27, 40]
Male sex	9 (60.0)
Race
African-American	9 (64.3)
White	5 (35.7)
Hispanic ethnicity	0
Physical signs and symptoms before treatment
Wheezing	13 (86.7)
Shortness of breath	13 (86.7)
Cough	9 (60.0)
Accessory muscle use	12 (80.0)
Medication in use
Inhaled albuterol	9 (60.0)
Inhaled corticosteroid	0
Systemic corticosteroid	1 (6.7)
Montelukast †	5 (33.3)
Last oral intake prior to study drug administration, hours, median [IQR]	2 [0.5, 6.0]

IQR, interquartile range

Values are n (%) unless otherwise specified

^†5 participants on chronic montelukast received most recent dose at 24, 30, 36, 48 and 48 hours prior to administration of study drug.

Montelukast plasma concentration-time profiles for each study participant are shown in Figure 1. Plasma concentrations according to blood sample acquisition times are presented in Table 2 and pharmacokinetic parameters in Table 3. The fixed-dose (30 mg) administration of montelukast to each participant resulted in a mean weight-based dose of 1.0 mg/kg (range: 0.5 – 1.8). Participant 4 had a very low concentration of montelukast in the baseline plasma sample; no montelukast was detected in baseline plasma samples for the remaining 14 participants. Montelukast exhibited a moderate to slow rate of absorption with a median t_max of 3.0 hours (range, 2–4) and high inter-individual variability in C_max with median C_max of 1378 ng/ml (range, 16 – 4895). Total montelukast drug exposure over time resulted in a median AUC_last of 2924 ngxhr/ml (range, 32 – 9016). Of note, montelukast was not detectable in participant 10 until two hours after drug administration with a C_max of 16 ng/ml.

Figure 1.

Individual plasma concentration-time profiles in 15 children aged 5–12 years after a 30 mg oral dose of montelukat chewable tablets. Profiles were generated from quantitative analysis of montelukat in plasma obtained from vacutainer blood collection tubes.

Table 2.

Blood sample acquisition times and plasma concentrations in 15 children aged 5 – 12 years with acute asthma exacerbations after administration of montelukast 30 mg as chewable tablets

		Blood sampling time after oral montelukast (minutes)
		0	15	30	45	60	120	180	240]
Number of participant samples		15	11	15	11	15	15	14	12
Plasma montelukast concentration, ng/ml	Median [IQR]	0 [0, 0]	10 [4, 46]	115 [46, 223]	237 [77, 396]	348 [123, 678]	938 [514, 1887]	1346 [929, 1967]	1279 [807, 1669]
	Mean (SD)	2.5 (9.7)	52 (119)	195 (291)	46 (2)	524 (549)	1136 (806)	1578 (1075)	1484 (1230)
	Range	0 – 38	0 – 406	0 – 1184	0 – 2043	0 – 2030	9 – 2769	16 – 4262	13 – 2895

IQR, interquartile range; SD, standard deviation

Table 3.

Plasma montelukast parameters generated from individual plasma concentrations-time profiles using noncompartmental pharmacokinetic analysis in 15 children aged 5 – 12 years with acute asthma exacerbations who received montelukast chewables (30 mg).

Parameter	Mean (SD)	Median	Range
Dose (mg/kg)	1.0 (0.4)	0.8	0.5 – 1.8
tmax (hours)	2.9 (0.7)	3.0	2.0 – 4.0
Cmax (ng/ml)	1,620 (1,196)	1,378	16 – 4,895
AUClast (ngxhr/ml)	3,579 (2,505)	2,924	32 – 9,017

C_max, peak plasma concentration; t_max, time to C_max; AUC_last, area under the concentration-time curve from 0 to the last time point in each subject

The primary pharmacokinetic endpoint for the study was to determine whether a 30 mg dose of oral montelukast could achieve a C_max of 1,700 ng/ml. Box and whisker plots for the mean and interquartile range for C_max are presented in Figure 2. Six of 15 participants (40%) achieved a C_max of 1,700 ng/ml or higher. Two of 15 participants reached the target C_max at 2 hours, 3 participants at 3 hours and 1 participant at 4 hours. Three participants were discharged prior to collecting a blood sample at 3 or 4 hours, two of whom had not yet achieved the target exposure threshold.

Figure 2.

Montelukast plasma concentrations at three time points after 30 mg montelukast chewable tablets in 15 children aged 5 – 12 years with acute asthma exacerbations. Boxes extend from 25^th to 75^th percemtile with median line across box and highest and lowest concentrations as fences. Dashed horizontal line is target C_max (1,700 ng/ml). Triangles are C_max values, once for each participant, with 5 at approximately 2 hours, 8 at approximately 3 hours, and 2 at approximately 4 hours. Circles are remaining sample values at each time point that are not Cmax.

All participants tolerated the study drug and none experienced any apparent side effects or adverse events during the 4 hour study period. The parent of each participant was contacted at 24–48 hours after study enrollment at the phone number provided by the parent. All participants tolerated the medication with no reports of adverse events or side effects.

Discussion

This investigation suggests that a 30 mg dose of oral montelukast chewable tablets results in C_max approaching 1,700 ng/ml in children aged 5 – 12 years with acute asthma exacerbations. This is a C_max that might provide benefit for pediatric patients with acute asthma exacerbations based on randomized trials and pharmacokinetic studies of IV montelukast in adults. ^27,28,30 Moreover, achieving this C_max around 3 hours is expected to improve lung function and decrease exacerbation severity within 4 hours of drug administration, based on clinical trials of the IV preparation.^27,28 This is the 4 hour time window to evaluate treatment response for the decision for hospital admission recommended by expert asthma guidelines.⁸ Additionally, no adverse events or side effects were observed in participants during the 4-hour study period or within 24 – 48 hour of study enrollment.

However, we observed significant inter-individual variability in montelukast C_max in comparison to the minimal variability observed in pharmacokinetic study of IV montelukast.³¹ This variability led to 40% of participants achieving the peak drug exposure of 1,700 ng/ml. The 11-fold variability in C_max (excluding participant 10) observed in this study is consistent with other studies reporting high inter-individual variability in oral montelukast drug exposure.³⁸ Therapeutic plasma concentrations after standard doses of oral montelukast are associated with a 15-fold variability.³⁹ A number of factors may contribute to this variability, including dose-dependent dissolution and absorption at the dose utilized in this study given its low solubility and dependence on carrier-mediated uptake by organic anion-transporting polypeptide (OATP) transporters expressed in the intestine.⁴⁰

The oral montelukast dose (30mg) used in this study is 6-fold greater than the typical oral dose, yet only a 3.3-fold increase in the mean C_max was observed in our study (1,620 ng/ml) compared to the previously reported mean C_max of 495 ng/ml in children administered a 5 mg chewable tablet. This observation, along with data from previous studies,^30,32 suggests a potential dose-dependent reduction in the rate or extent of absorption that may contribute to higher inter-individual variability within this population. Although our blood sampling window was limited to 4 hours after drug administration, examination of the plasma-concentration time profiles in our study suggests a relatively flat exposure profile between 2 and 4 hours that may also indicate the influence of dissolution or capacity-limited absorption on peak montelukast exposure.

Genetic factors may also contribute to differences in absorption through variation in drug transporters. The organic anion-transporting polypeptide OATP transporters are known to contribute to montelukast uptake in intestinal mucosal cells and hepatocytes,^40,41 and function-altering variants in the genes encoding these transporters are common in many populations. Prior studies have demonstrated associations between montelukast kinetics and variants in OATP2B1 (encoded by SLCO1B1) and OATP1B1 (encoded by SLCO1B1).^42–44 Variations in ATP binding cassette (ABC) subfamily C member 9 (encoded by ABCC9) have been associated with the AUC for the M5R hydroxy-metabolite of montelukast.⁴⁴ Another variant in ABC member 1 (ABCC1, also known as MRP1, encoding Multidrug Resistance-Associated Protein 1) has been associated with montelukast efficacy, which is likely due to differences in drug disposition.⁴⁵

Individual differences in drug metabolism may also contribute variability. Montelukast metabolism includes activation by the cytochrome P450 (CYP) enzymes 2C8, 2C9, and 3A4, as well as UDP-glucuronosyltransferase (UGT) 1A3.^46,47 Variants in CYP2C8 and UGT1A3 have been associated with pharmacokinetics of montelukast and/or the metabolites.⁴⁴ Before proceeding to clinical trials of this drug for acute asthma exacerbations, it is necessary to perform dose-finding studies that include pharmacogenomic analyses. These investigations may advance precision medicine for children with acute asthma that will minimize use of corticosteroids.

One limitation to our study is that we did not investigate these potential pharmacogenomic associations. Pharmacogenomic studies require a large enough sample size for adequate power to detect a statistically significant difference. Many pediatric pharmacogenomic studies for drugs, including montelukast, have reported negative findings that may be due to inadequate sample size.^48,49 Our study of 15 individuals is not sufficiently powered to provide insights regarding which, if any, of the candidate genes above play a role in the inter-individual variation that we observed, and a larger study may lead to personalized approaches to montelukast dosing for asthma exacerbations. We followed up with study participants and families to assess for adverse effects of high-dose montelukast and found none, but our small sample size does not eliminate the possibility of toxicity. Our study enrolled a convenience sample of children in the ED, and did not control for prior oral intake, which may have significantly contributed to the observed variability in C_max.

In this pilot pharmacokinetic study, we also did not collect data regarding drug response or therapeutic effect. Indeed, it is not known whether Cmax, time-on-target, or AUC is the primary determinant of high-dose montelukast efficacy during acute asthma exacerbations. Greater knowledge of the pharmacokinetic-pharmacodynamic relationship, weight-based dosing data, and efficacy data must be established prior to use of high-dose montelukast for acute asthma exacerbations.

Conclusions

To our knowledge, this is the first prospective study to describe the C_max and tolerability of high-dose oral montelukast in children admitted to the emergency department with acute asthma exacerbations. Chewable Montelukast tablets at a dose of 30 mg result in C_max approaching a target concentration expected to provide improvement of lung function for acute asthma exacerbations in children. Dose-ranging studies are needed that include a sufficient number of participants powered for important clinical outcomes and that control for food intake and genetic variables.