Single dose pharmacokinetics, safety and tolerability of MK-0476, a new leukotriene D4-receptor antagonist, in healthy volunteers

New chemometrics-assisted spectrophotometric methods for simultaneous determination of co-formulated drugs montelukast, rupatadine, and desloratadine in their different dosage combinations

Two accurate, precise and robust multivariate chemometric methods were developed for the simultaneous determination of montelukast sodium (MON), rupatadine fumarate (RUP) and desloratadine (DES). These methods provide a cost-effective alternative to chromatographic techniques by utilizing spectrophotometry in pharmaceutical quality control. The proposed approaches, partial least squares-1 (PLS-1) and artificial neural network (ANN), were optimized using genetic algorithm (GA) to select the most influential wavelengths, enhancing model performance. A five-level, three-factor design was employed to construct a calibration set with 25 mixtures, utilizing concentration ranges of 3-19, 5-25, and 4-20 µg.mL-1 for MON, RUP, and DES, respectively. An independent validation set was employed to assess the performance of the models. GA significantly improved the PLS-1 and ANN models for RUP and DES, though minimal enhancement was observed for MON. These methods were successfully applied to the simultaneous quantification of the compounds in pharmaceutical formulations and proved useful as stability-indicating assays for RUP, given that DES is a known degradation product. The developed methods offer a valuable tool for impurity profiling and quality control in pharmaceutical analysis.

Promising treatment biomarkers in asthma

Asthma is a highly heterogenous disease which researchers over time have attempted to classify into different phenotypes and endotypes to improve diagnosis, prognosis and treatment. Earlier classifications based on reaction to environmental allergens, age, sex and lung function have evolved, and today, the use of precision medicine guided by biomarkers offers new perspectives on asthma management. Identifying biomarkers that may reveal the underlying pathophysiology of the disease will help to select the patients who will benefit most from specific treatments. This review explores the classification of asthma phenotypes and focuses on the most recent advances in using biomarkers to guide treatment.

Styryl Group, a Friend or Foe in Medicinal Chemistry

The styryl (Ph-CH=CH-R) group is widely represented in medicinally important compounds, including drugs, clinical candidates, and molecular probes as it positively impacts the lipophilicity, oral absorption, and biological activity. The analysis of matched molecular pairs (styryl vs. phenethyl, phenyl, methyl, H) for the biological activity indicates the superiority aspect of styryl compounds. However, the Michael acceptor site in the styryl group makes it amenable to the nucleophilic attack by biological nucleophiles and transformation to the toxic metabolites. One of the downsides of styryl compounds is isomerization that impacts the molecular conformation and directly affects biological activity. The impact of cis-trans isomerism and isosteric replacements on biological activity is exemplified. We also discuss the styryl group-bearing drugs, clinical candidates, and fluorescent probes. Overall, the present review reveals the utility of the styryl group in medicinal chemistry and drug discovery.

Montelukast suppresses the development of irritable bowel syndrome phenotype possibly through modulating NF-κB signaling in an experimental model

Irritable bowel syndrome (IBS) is a functional gut disorder with multi-factorial pathophysiology that causes recurring pain or discomfort in the abdomen, as well as altered bowel habits. Montelukast, a well-known cysteinyl leukotriene receptor 1 (CysLT1R) antagonist, is widely used for the anti-inflammatory management of asthma. The present study aimed to evaluate the effects of pharmacological inhibition of CysLT1R on acetic acid-induced diarrhea-predominant IBS (D-IBS) in rats. Behavioral pain responses to noxious mechanical stimulation were decreased in the montelukast-treated rats as compared to the model animals following colorectal distension (CRD)-induced visceral hypersensitivity. Stool frequency decreased dose-dependently by montelukast in IBS rats exposed to restraint stress. A significantly shorter immobility time was also observed in IBS rats who received montelukast vs IBS group in the forced swimming test (depression-like behavior). Furthermore, there were significant decreases in the NF-κB protein expression, inflammatory cytokine (TNF-α, and IL-1ß) levels, and histopathological inflammatory injuries concomitant with increased anti-inflammatory cytokine, IL-10, in montelukast-treated rats compared with the IBS group. Cysteinyl leukotriene production and CysLT1R mRNA expression showed no remarkable differences among the experimental groups. The present results suggest the possible beneficial effects of montelukast in the management of D-IBS symptoms. The molecular mechanism underlying such effects, at least to some extent, might be through modulating CysLT1R-mediated NF-κB signaling. Yet, more studies are required to demonstrate the clinical potential of this drug for IBS therapy.

The Leukotriene Receptor Antagonist Montelukast as a Potential COVID-19 Therapeutic

The emergence and global impact of COVID-19 has focused the scientific and medical community on the pivotal influential role of respiratory viruses as causes of severe pneumonia, on the understanding of the underlying pathomechanisms, and on potential treatment for COVID-19. The latter concentrates on four different strategies: (i) antiviral treatments to limit the entry of the virus into the cell and its propagation, (ii) anti-inflammatory treatment to reduce the impact of COVID-19 associated inflammation and cytokine storm, (iii) treatment using cardiovascular medication to reduce COVID-19 associated thrombosis and vascular damage, and (iv) treatment to reduce the COVID-19 associated lung injury. Ideally, effective COVID-19 treatment should target as many of these mechanisms as possible arguing for the search of common denominators as potential drug targets. Leukotrienes and their receptors qualify as such targets: they are lipid mediators of inflammation and tissue damage and well-established targets in respiratory diseases like asthma. Besides their role in inflammation, they are involved in various other aspects of lung pathologies like vascular damage, thrombosis, and fibrotic response, in brain and retinal damages, and in cardiovascular disease. In consequence, leukotriene receptor antagonists might be potential candidates for COVID-19 therapeutics. This review summarizes the current knowledge on the potential involvement of leukotrienes in COVID-19, and the rational for the use of the leukotriene receptor antagonist montelukast as a COVID-19 therapeutic.

The leukotriene receptors as therapeutic targets of inflammatory diseases

Leukotrienes (LTs) are inflammatory mediators derived from arachidonic acid. LTs include the di-hydroxy acid LT (LTB4) and the cysteinyl LTs (CysLTs; LTC4, LTD4 and LTE4), all of which are involved in both acute and chronic inflammation. We and other groups identified a high-affinity LTB4 receptor, BLT1; the LTC4 and LTD4 receptors, CysLT1 and CysLT2; and the LTE4 receptor, GPR99. Pharmacological studies have shown that BLT1 signaling stimulates degranulation, chemotaxis and phagocytosis of neutrophils, whereas CysLT1 and CysLT2 signaling induces airway inflammation by increasing vascular permeability and the contraction of bronchial smooth muscle. Recently, we and other groups suggested that the LTB4-BLT1 axis and the cysteinyl LTs-CysLT1/2 axis are involved in chronic inflammatory diseases including asthma, atopic dermatitis, psoriasis, atherosclerosis, arthritis, obesity, cancer and age-related macular degeneration using animal models for disease and gene knockout mice. This review describes the classical and novel functions of LTs and their receptors in several inflammatory diseases and discusses the potential clinical applications of antagonists for LT receptors and inhibitors of LT biosynthesis.

G Protein-Coupled Receptors in Asthma Therapy: Pharmacology and Drug Action

Asthma is a heterogeneous inflammatory disease of the airways that is associated with airway hyperresponsiveness and airflow limitation. Although asthma was once simply categorized as atopic or nonatopic, emerging analyses over the last few decades have revealed a variety of asthma endotypes that are attributed to numerous pathophysiological mechanisms. The classification of asthma by endotype is primarily routed in different profiles of airway inflammation that contribute to bronchoconstriction. Many asthma therapeutics target G protein-coupled receptors (GPCRs), which either enhance bronchodilation or prevent bronchoconstriction. Short-acting and long-acting β 2-agonists are widely used bronchodilators that signal through the activation of the β 2-adrenergic receptor. Short-acting and long-acting antagonists of muscarinic acetylcholine receptors are used to reduce bronchoconstriction by blocking the action of acetylcholine. Leukotriene antagonists that block the signaling of cysteinyl leukotriene receptor 1 are used as an add-on therapy to reduce bronchoconstriction and inflammation induced by cysteinyl leukotrienes. A number of GPCR-targeting asthma drug candidates are also in different stages of development. Among them, antagonists of prostaglandin D2 receptor 2 have advanced into phase III clinical trials. Others, including antagonists of the adenosine A2B receptor and the histamine H4 receptor, are in early stages of clinical investigation. In the past decade, significant research advancements in pharmacology, cell biology, structural biology, and molecular physiology have greatly deepened our understanding of the therapeutic roles of GPCRs in asthma and drug action on these GPCRs. This review summarizes our current understanding of GPCR signaling and pharmacology in the context of asthma treatment. SIGNIFICANCE STATEMENT: Although current treatment methods for asthma are effective for a majority of asthma patients, there are still a large number of patients with poorly controlled asthma who may experience asthma exacerbations. This review summarizes current asthma treatment methods and our understanding of signaling and pharmacology of G protein-coupled receptors (GPCRs) in asthma therapy, and discusses controversies regarding the use of GPCR drugs and new opportunities in developing GPCR-targeting therapeutics for the treatment of asthma.

Amenamevir: Studies of Potential CYP2C8- and CYP2B6-Mediated Pharmacokinetic Interactions With Montelukast and Bupropion in Healthy Volunteers

Amenamevir (formerly ASP2151) induces cytochrome P450 (CYP)2B6 and CYP3A4 and inhibits CYP2C8.  We conducted 2 studies, 1 using montelukast as a probe to assess CYP2C8 and the other bupropion to assess CYP2B6.  The montelukast study examined the effect of amenamevir on the pharmacokinetics of montelukast in 24 healthy men: each subject received montelukast 10 mg alone, followed by montelukast 10 mg with amenamevir 400 mg, or vice versa after a washout period.  In the bupropion study, 24 subjects received a single dose of 150 mg bupropion on days 1, 15, 22, and 29, and repeated once-daily doses of 400 mg amenamevir on days 6-15.  Amenamevir increased peak concentration and area under the concentration-time curve of montelukast by about 22% (ratio 121.7%, 90%CI [114.8, 129.1]; 121% [116.2, 128.4], respectively) with a similar increase in hydroxymontelukast (ratio 121.4%, 90%CI [106.4, 138.5]; 125.6 % [111.3, 141.7]).  Amenamevir reduced peak concentration and area under the concentration-time curve of bupropion by 16% (84.29%, 90%CI [78.00, 91.10]; 84.07%, 90%CI [78.85, 89.63]), with recovery after 1 week; the pharmacokinetics of the primary metabolite hydroxybupropion was unaffected.  Thus, amenamevir increased plasma concentrations of montelukast and decreased those of bupropion, but it did not do so enough to require dose adjustment of coadministered substrates of either CYP2C8 or CYP2B6.

Adverse events are rare after single-dose montelukast exposures in children

STUDY OBJECTIVE

Montelukast sodium is a leukotriene-receptor antagonist approved as a controller medication for chronic asthma and allergic rhinitis in children and adults. We sought to characterize adverse events associated with single montelukast exposures in children ages 5-17 years and to determine whether adverse events were dose related for all-dose and for ultra-high-dose (≥50 mg) exposures.

METHODS

This is a retrospective analysis of data from the National Poison Data System for exposures that included montelukast in individuals aged 5-17 years for calendar years 2000-2016. Filters were applied to identify exposure events in which montelukast was the primary exposure and for which the exact or lowest-possible ingested dose was recorded. Characteristics of adverse events were examined using descriptive statistics and multivariable logistic models were used to examine whether associations of montelukast and adverse events were dose related.

RESULTS

During the 17-year study period, there were 17,069 montelukast exposures available for analyses. Patients were median [interquartile range] age 7 (5, 9) years, and 10,907 (64%) male gender. Abdominal pain was the most common adverse event (0.23%). There were 618 ultra-high-dose exposures (≥50 mg). These patients had median age 6 (5, 8) years, and 347 (56%) male gender. Abdominal pain was the most common adverse event (1.46%). Increasing ingested dose was associated with abdominal pain (adjusted odds ratio, 1.01, 95% confidence interval 1.01, 1.02) after adjustment for age and gender. No serious or life-threatening events were reported.

CONCLUSIONS

Single-dose exposures of montelukast up to 445 mg are rarely associated with any adverse events and are not associated with serious or life-threatening adverse events in children aged 5-17 years.

Pediatric acute asthma exacerbations: Evaluation and management from emergency department to intensive care unit

OBJECTIVE

The goal of this report is to review available modalities for assessing and managing acute asthma exacerbations in pediatric patients, including some that are not included in current expert panel guidelines. While it is not our purpose to provide a comprehensive review of the National Asthma Education and Prevention Program (NAEPP) guidelines, we review NAEPP-recommended treatments to provide the full range of treatments available for managing exacerbations with an emphasis on the continuum of care between the ER and ICU.

DATA SOURCES

We searched PubMed using the following search terms in different combinations: asthma, children, pediatric, exacerbation, epidemiology, pathophysiology, guidelines, treatment, management, oxygen, albuterol, β2-agonist, anticholinergic, theophylline, corticosteroid, magnesium, heliox, BiPAP, ventilation, mechanical ventilation, non-invasive mechanical ventilation and respiratory failure. We attempted to weigh the evidence using the hierarchy in which meta-analyses of randomized controlled trials (RCTs) provide the strongest evidence, followed by individual RCTs, followed by observational studies. We also reviewed the NAEPP and Global Initiative for Asthma expert panel guidelines.

RESULTS AND CONCLUSIONS

Asthma is the most common chronic disease of childhood, and acute exacerbations are a significant burden to patients and to public health. Optimal assessment and management of exacerbations, including appropriate escalation of interventions, are essential to minimize morbidity and prevent mortality. While inhaled albuterol and systemic corticosteroids are the mainstay of exacerbation management, escalation may include interventions discussed in this review.

Protective effect of high-dose montelukast on salbutamol-induced homologous desensitisation in airway smooth muscle

Montelukast (MK) is a potent cysteinyl-leukotriene receptor antagonist that causes dose-related improvements in chronic asthma. We sought to determine whether MK was able to prevent salbutamol-induced tolerance in airway smooth muscle. Homologous β2-adrenoceptor desensitisation models were established in guinea-pigs and in human bronchial smooth muscle cells (BSMC) by chronic salbutamol administration. Characterisation tools included measurement of the response of tracheal smooth muscle tissues to salbutamol, analysis of gene expression and receptor trafficking, evaluation of intracellular cAMP levels and phosphodiesterase (PDE) activity in human bronchial smooth muscle cells. Salbutamol-induced β2-adrenoceptor desensitisation was characterised by β2-agonist hyporesponsiveness (-30%, p < 0.001) in desensitised tracheal smooth muscle, as compared to controls. MK, given intraperitoneally at 5 mg/kg/day for 6 consecutive days, completely restored tissue responsiveness to salbutamol. Prolonged salbutamol treatment significantly decreased cAMP synthesis, induced a complete removal of the β2-adrenoceptor from plasma membrane with a parallel increase in the cytosol and increased PDE4D5 gene transcription and PDE activity in human bronchial smooth muscle cells. In homologously desensitised BSMC, MK 30 μM for 24 h was able to prevent salbutamol subsensitivity and such an effect was associated with inhibition of salbutamol-induced PDE4 activity and restoration of membrane β2-adrenoceptor expression and function. These findings suggest the presence of a favourable interaction between MK and β2-adrenoceptor agonists that might improve the therapeutic index of bronchodilators in patients with chronic respiratory diseases.

Concentration-dependent noncysteinyl leukotriene type 1 receptor-mediated inhibitory activity of leukotriene receptor antagonists

The use of cysteinyl leukotriene receptor antagonists (LTRAs) for asthma therapy has been associated with a significant degree of interpatient variability in response to treatment. Some of that variability may be attributable to noncysteinyl leukotriene type 1 receptor (CysLT(1))-mediated inhibitory mechanisms that have been demonstrated for this group of drugs. We used a model of CysLT(1) signaling in human monocytes to characterize CysLT(1)-dependent and -independent anti-inflammatory activity of two chemically different, clinically relevant LTRAs (montelukast and zafirlukast). Using receptor-desensitization experiments in monocytes and CysLT(1)-transfected HEK293 cells and IL-10- and CysLT(1) small interfering RNA-induced downregulation of CysLT(1) expression, we showed that reported CysLT(1) agonists leukotriene D(4) and UDP signal through calcium mobilization, acting on separate receptors, and that both pathways were inhibited by montelukast and zafirlukast. However, 3-log greater concentrations of LTRAs were required for the inhibition of UDP-induced signaling. In monocytes, UDP, but not leukotriene D(4), induced IL-8 production that was significantly inhibited by both drugs at micromolar concentrations. At low micromolar concentrations, both LTRAs also inhibited calcium ionophore-induced leukotriene (leukotriene B(4) and leukotriene C(4)) production, indicating 5-lipoxygenase inhibitory activities. We report herein that montelukast and zafirlukast, acting in a concentration-dependent manner, can inhibit non-CysLT(1)-mediated proinflammatory reactions, suggesting activities potentially relevant for interpatient variability in response to treatment. Higher doses of currently known LTRAs or new compounds derived from this class of drugs may represent a new strategy for finding more efficient therapy for bronchial asthma.

Determination of montelukast sodium by capillary electrophoresis

This work verifies the potential of CE in the analysis of significant impurities of montelukast sodium - an active ingredient for the treatment of bronchial asthma. Using 20 mM borate buffer pH 9.2 with 10 mM SDS and 10 mM (2-hydroxypropyl)-gamma-CD (2HP-gamma-CD) it was possible to separate montelukast and several impurities, including its cis-isomer, after exposure to light and oxygen. The obtained method surpasses a chromatographic method for montelukast sodium in terms of time of analysis (9 min of CE analysis vs. 35 min HPLC) and efficiency (CE offered over 900 000 theoretical plates for montelukast). Good repeatability of the method was supported by the low % RSD for the migration time of montelukast (0.53%). For the first time, the capillary electrophoretic method was employed for temporal study of the degradation of montelukast. The results showed that degradation of montelukast and the formation of the cis-isomer mainly occurred during the first 2 days of exposure, and occurred to a higher degree when there was no contact with the air (oxygen) in the exposed sample.

Effect of light and heat on the stability of montelukast in solution and in its solid state

The chemical stability of montelukast (Monte) in solution and in its solid state was studied. A simultaneous measurement of Monte and its degradation products was determined using a selective HPLC method. The HPLC system comprised a reversed phase column (C18) as the stationary phase and a mixture of ammonium acetate buffer of pH 3.5 and methanol (15:85 v/v) as the mobile phase. The UV detection was conducted at 254 nm. Monte in solution showed instability when exposed to light leading to the formation of its cis-isomer as the major photoproduct. The rate of photodegradation of Monte in solution exposed to various light sources increases in the order of; sodium<neon<tungsten<daylight<UV (254 nm). The extent of photodegradation was influenced by solvent type, where Monte was found to be most stable in 70% methanol. In solid state, Monte showed more than 20% decrease in its potency after exposure to daylight for 1 week. Also unpacked Monte chewable tablets, exposed to daylight for 2 weeks, showed a decrease of about 10% with the formation of Monte S-oxide as a major photoproduct. On the other hand, Monte film-coated tablets either unpacked or in its immediate pack showed excellent stability under the same condition. The thermal stress testing study of Monte in solutions at 65 degrees C showed that it is highly stable in NaOH solution, while it degrades rapidly in both acidic and H2O2 solutions. The major degradation product in the latter solvent was Monte S-oxide and it was also detected as a major degradation product in Monte tablet dosage form during the incubation at 40 degrees C/75% RH for 6 months. Findings of this study have helped to understand the stability behavior of Monte and to establish the critical parameters, which may affect its analysis and manufacturing activities.

A population pharmacokinetic model for montelukast disposition in adults and children

PURPOSE

The purpose was to develop a population pharmacokinetic model for montelukast after intravenous administration. Clinical trial simulations were conducted using the model developed to identify the lowest intravenous dose in 6- to 14-year-old children that would give montelukast systemic exposures that were comparable to those found to be associated with efficacy in adults.

METHODS

Two clinical studies were conducted where montelukast was administered intravenously as a 7-mg dose to adults and as a 3.5-mg dose to children aged 6 to 14 years. Model development included defining the base pharmacostatistical model and investigating the effects of demographic variables [age and total body weight (TBW)] on the structural parameters, using a nonlinear mixed effect modeling approach.

RESULTS

A linear three-compartment pharmacokinetic model was found to best describe the disposition of montelukast. Inclusion of TBW as a covariate caused a 35% and 63% decrease in the interindividual variabilities on clearance and central volume of distribution, respectively. Trial simulations suggested that a 5.25-mg intravenous dose of montelukast should be chosen in children aged 6 to 14 years.

CONCLUSIONS

The model developed can adequately describe the intravenous pharmacokinetics of montelukast and can be used as a useful tool for dose selection in pediatric subpopulations.

Pharmacokinetics of montelukast in asthmatic patients 6 to 24 months old

Montelukast is a cysteinyl leukotriene receptor antagonist approved for the treatment of asthma for those ages 1 year old to adult. The purpose of this study was to evaluate the pharmacokinetic comparability of a 4-mg dose of montelukast oral granules in patients > or = 6 to < 24 months old to the 10-mg approved dose in adults. This was an open-label study in 32 patients. Population pharmacokinetic parameters included estimates of AUC(pop), C(max), and t(max). Results were compared with estimates from adults (10-mg film-coated tablet [FCT]). Dose selection criteria were for the 95% confidence interval (CI) for the AUC(pop) estimate ratio (pediatric/adult 10 mg FCT) to be within comparability bounds of (0.5, 2.00). The AUC(pop) ratio and the 95% CI for children compared with adults were within the predefined comparability bounds. Observed plasma concentrations were also similar. Based on systemic exposure of montelukast, a 4-mg dose of montelukast appears appropriate for children as young as 6 months of age.

Montelukast-induced generalized urticaria

OBJECTIVE

To report a case of generalized urticaria induced by montelukast treatment.

CASE SUMMARY

A 28-year-old man with allergic rhinitis and moderate persistent asthma developed generalized urticaria 5 days after the initiation of montelukast and inhaled fluticasone. Symptoms disappeared within one day after suspension of both drugs. Two months later, after the resumption of montelukast and fluticasone, the patient developed generalized urticaria and eyelid angioedema, which were successfully treated with intravenous betamethasone, achieving complete remission within hours. After 2 days, the patient resumed inhaled fluticasone only and continued this therapy for several months without any adverse reaction.

DISCUSSION

We attributed the adverse reaction to montelukast because of the temporal relationship between use of montelukast and urticaria, the absence of other identified causative factors and other explanations for allergic reactions, and the positive dechallenge and rechallenge. The Naranjo probability scale showed a probable relationship between skin manifestations and montelukast treatment.

CONCLUSIONS

The use of antileukotrienes is increasing in asthma therapy. In cases of generalized urticaria in asthmatic patients undergoing montelukast therapy, physicians should be aware of a potential adverse reaction to this drug.

Benefit-risk assessment of antileukotrienes in the management of asthma

Antileukotrienes are a relatively new class of anti-asthma drugs that either block leukotriene synthesis (5-lipoxygenase inhibitors) like zileuton, or antagonise the most relevant of their receptors (the cysteinyl leukotriene 1 receptor [CysLT1]) like montelukast, zafirlukast or pranlukast. Hence, their major effect is an anti-inflammatory one. With the exception of pranlukast, the other antileukotrienes have been studied and marketed in the US and Europe for long enough to establish that they are useful drugs in the management of asthma. Their effects, significantly better than placebo, seem more pronounced in subjective measurements (i.e. symptoms scores or quality-of-life tests) than in objective parameters (i.e. forced expiratory volume in 1 second or peak expiratory flow rate). Also, there is some evidence that these drugs work better in some subsets of patients with certain genetic polymorphisms - probably related to their leukotriene metabolism - or patients with certain asthma characteristics. There are a small number of comparative studies only, and with regard to long-term asthma control differences between the agents have not been evaluated. Nevertheless, their overall effect appears comparable with sodium cromoglycate (cromolyn sodium) or theophylline, but significantly less than low-dose inhaled corticosteroids. Antileukotrienes have been shown to have a degree of corticosteroid-sparing effect, but salmeterol appears to perform better as an add-on drug. Montelukast is probably the most useful antileukotriene for continuous treatment of exercise-induced asthma, performing as well as salmeterol without inducing any tolerance. All antileukotrienes are taken orally; their frequency of administration is quite different ranging from four times daily (zileuton) to once daily (montelukast). Antileukotrienes are well tolerated drugs, even though zileuton intake has been related to transitional liver enzyme elevations in some cases. Also Churg-Strauss syndrome (a systemic vasculitis), has been described in small numbers of patients taking CysLT1 antagonists. It is quite probable that this disease appears as a consequence of an 'unmasking' effect when corticosteroid dosages are reduced in patients with severe asthma once CysLT1 antagonists are introduced, but more data are needed to definitely establish the mechanism behind this effect. Overall, however, the benefits of antileukotrienes in the treatment of asthma greatly outweigh their risks.

Anti-inflammatory effects of high-dose montelukast in an animal model of acute asthma

BACKGROUND

Asthmatic inflammation is mediated by a network of cytokines, chemokines and adhesion molecules. Corticosteroids are the only effective agents available to control asthmatic inflammation. We investigated the effect of high-dose montelukast (MK), a selective cysteinyl leukotriene receptor 1 antagonist, on mediators of airway inflammation.

OBJECTIVE

The aim of this study was to determine the effect of a 3-day course of high-dose MK on mediators of airway inflammation induced by a single allergen challenge in sensitized mice.

METHODS

Ovalbumin (OVA)-sensitized BALB/c mice were treated with 25 mg/kg of MK or saline intravenously for 3 days. On the third day, a single inhalation challenge with OVA was given. Cellular infiltration was assessed in the bronchoalveolar lavage (BAL) and in the lung. Expression of IL-4, IL-5, IL-13 and eotaxin in the BAL, and the lung was determined. Serum IL-5 and total IgE was measured. IL-5 and eotaxin mRNA expression in the lung was determined. Finally, eotaxin and VACM-1 expression in the lung was assessed by immunohistochemistry.

RESULTS

MK reduced the number of eosinophils in the BAL by > 90%. There was also significant reduction in IL-5 in the BAL, lung and the serum, and IL-5 mRNA expression in the lung. IL-4 level in the lung and BAL, and IL-13 level in the lung also significantly decreased. Serum IgE level and lung VCAM-1 expression was also significantly lower in treated animals, but eotaxin protein and mRNA expression in the lung remained unchanged.

CONCLUSION

MK exerts its anti-inflammatory effect through the suppression of T helper type-2 (Th2) cytokines. The use of high-dose MK as an anti-inflammatory agent in acute asthma should be further explored.

Simultaneous determination of montelukast and loratadine by HPLC and derivative spectrophotometric methods

In this study, high performance liquid chromatography (HPLC) and second derivative spectrophotometry have been used and described for the simultaneous determination of montelukast and loratadine in pharmaceutical formulations. HPLC separation was achieved with a Symmetry C18 column and sodium phosphate buffer (pH adjusted to 3.7): acetonitrile (20:80, v/v) as eluent, at a flow rate of 1.0 ml/min. UV detection was performed at 225 nm. The LC method is simple, rapid, selective and stability indicating for the determination of montelukast. 5-Methyl 2-nitrophenol was used as internal standard for the purpose of quantification of both the drugs in HPLC. In the second-order derivative spectrophotometry, for the determination of loratadine the zero-crossing technique was applied at 276.1 nm, but for montelukast peak amplitude at 359.7 nm (tangent method) was used. Both methods were fully validated and a comparison was made for assay determination of selected drugs in formulations. The results confirm that the methods are highly suitable for its intended purpose.

Time efficacy of a single dose of montelukast on exercise-induced asthma in children

The aim of this study was to evaluate the timing of onset and the duration of action of a single oral-dose treatment with montelukast in comparison to placebo on exercise-induced asthma (EIA) in asthmatic children. Nineteen children (7-13 years) with stable asthma were evaluated. Patients undertook three consecutive treadmill exercise tests, respectively, 2, 12 and 24 h after a single-dose administration. A double-blind randomized, single-dose, placebo-controlled, crossover design was used. To assess bronchoconstriction after the exercise challenge, the maximal percentage fall in FEV1 (DeltaFEV1) from the baseline value was considered. Two hours after dosing, DeltaFEV1 was -15.33 +/- 2.93 for placebo and -13.33 +/- 2.03 for montelukast. At 12 h, DeltaFEV1 was -18.69 +/- 2.83 for placebo, -9.78 +/- 1.85 for montelukast (p < 0.005). No difference was observed between placebo (DeltaFEV1-10.21 +/- 2.07) and montelukast (DeltaFEV1-9.10 +/- 2.02) at 24 h. Analysis of the degree of protection showed a significant efficacy of montelukast (p = 0.02) in comparison with placebo only at 12 h. Montelukast showed a significant protective effect 12 h after dosing, but no effect after 2 and 24 h. In mild asthmatics, the timing of administration of single dosage before exercise should be strictly considered in order to obtain the drug protective effects.

Drugs for the treatment of allergic diseases

Many kinds of drugs are used for the treatment of allergic diseases. Glucocorticoids are the most efficacious drugs and widely used for the treatment of allergic diseases. Recently, effectiveness of inhaled glucocorticoids for the treatment of bronchial asthma has been established. Beclomethasone dipropionate and fluticasone propionate, which are degraded easily after absorption, are applied by inhalation. Histamine is one of the most important mediators in allergic reactions and antihistamines have widely been applied for the treatment of allergic skin diseases. In Japan, over 20 antiallergic drugs, such as mediator release inhibitors, mediator antagonists and mediator synthesis inhibitors, have been developed. Recently developed compounds such as pranlukast and suplatast are very effective. To relieve the asthmatic attack, bronchodilators such as beta2-adrenoceptor agonists, theophylline and anti-cholinergic drugs are used. Clinical application of tacrolimus ointment has just started for the treatment of atopic dermatitis. Recently the number of allergic patients has increased. The onset and development of allergic diseases are considered to be dependent on both the genetic factors and the environmental factors. For the successful treatment of patients with allergic diseases, it is also important to consider the control of environmental factors.

Montelukast dose selection in children ages 2 to 5 years: comparison of population pharmacokinetics between children and adults

Montelukast, a leukotriene receptor antagonist, has demonstrated efficacy and tolerability in the treatment of asthma in patients age 6 years and older. The purpose of this open, one-period, multicenter population pharmacokinetic study was to identify a chewable tablet (CT) dose of montelukast for administration to children ages 2 to 5 years with asthma, yielding a single-dose pharmacokinetic profile (area under the plasma concentration-time curve [AUC]) comparable to that of the 10 mg film-coated tablet (FCT) dose in adults. Because patient numbers were small and the volume of blood that could be collected from individual 2- to 5-year-old patients was limited, a population pharmacokinetic approach was used to estimate population AUC (AUCpop). The 4 mg CT dose of montelukast was well tolerated and yielded an AUCpop (2721 ng.h/mL) similar to that of the adult AUCpop (2595 ng.h/mL) observed after a 10 mg FCT dose. These results support the selection of a 4 mg once-daily CT dose of montelukast for future efficacy and safety studies in children ages 2 to 5 years with asthma.

Antileukotrienes in asthma: present situation

Leukotrienes are key mediators in asthma. Over the last 5 years, several antileukotrienes, including three receptor antagonists (montelukast, pranlukast and zafirlukast) and one 5-lipoxygenase inhibitor (zileuton), have been marketed and, to date, this class of drugs is being used widely. Still, their definite place in the asthma treatment algorithm is not yet established. These novel drugs have not yet all been evaluated in the same depth, but they have all been shown to possess anti-inflammatory properties and to be effective in chronic asthma treatment. Zafirlukast and montelukast are particularly efficacious in exercise-induced asthma and zileuton appears valuable for treating aspirin-intolerant asthmatics. Clinical comparisons to other anti-asthma drugs are still sparse. The corticosteroid-sparing effect of antileukotrienes is fairly well established except for zileuton, even though this drug has been evaluated most thoroughly in terms of its anti-inflammatory effects. Montelukast is the antileukotriene most extensively evaluated in children and zafirlukast has recently been approved for use in children in the USA, although not yet in Europe. Therapeutic regimes are quite variable depending on the drug, but all of the antileukotrienes marketed to date are taken orally; hence, compliance is usually greater than that with inhaled medication. Response to antileukotrienes appears to depend on the individual patients' characteristics, in particular on genetic polymorphisms related to leukotriene metabolism. All drugs of this class are well tolerated and only in the case of zileuton is there potential for hepatic adverse effects. The diagnosis of Churg-Strauss syndrome made among patients taking antileukotrienes seems to be more related to the withdrawal of corticosteroids than to the antileukotrienes themselves.

Montelukast adult (10-mg film-coated tablet) and pediatric (5-mg chewable tablet) dose selections

Montelukast is a selective leukotriene receptor antagonist that has been shown to be effective in the treatment of chronic asthma. It is approved in more than 70 countries for patients 6 years of age and older. For adults (> or = 15 years of age), a 10-mg film-coated tablet (FCT) is available, and for children (aged 6 to 14 years), a 5-mg chewable tablet (CT) is available. The adult montelukast dose (10-mg FCT) was selected on the basis of classic dose-ranging studies as the lowest dose that produces maximal improvement in both measures of airway function and patient-reported outcomes in chronic asthma and in the attenuation of exercise-induced bronchoconstriction. The strategy used for the pediatric dose selection for montelukast was based on the determination of a CT dose that would provide an overall systemic exposure to montelukast in children similar to that in adults who receive a 10-mg FCT dose. Because montelukast was to be given chronically for the treatment of asthma, the area under the plasma concentration-time curve was considered to be the pharmacokinetic measurement that best represented systemic exposure to the drug. A 5-mg CT yielded a comparable single-dose area under the plasma concentration-time curve profile to that of the adult 10-mg FCT dose and, therefore, was selected as the pediatric dose for children aged 6 to 14 years with asthma. Subsequently, 2 studies of efficacy and tolerability validated the choice of the 5-mg CT dose.

Montelukast: data from clinical trials in the management of asthma

OBJECTIVE

To review the pharmacology, pharmacokinetics, clinical efficacy, and adverse effects of montelukast, a leukotriene receptor antagonist used to treat asthma, and to discuss the therapeutic role of montelukast as long-term medication and difficulties associated with the management of asthma.

DATA SOURCES

A MEDLINE search (up to May 1999) was conducted to identify relevant English-language publications, including preclinical studies, clinical trials, and recent reviews.

STUDY SELECTION

All available published reports of controlled, clinical trials of montelukast in adults and children with asthma were summarized, including pharmacokinetic and pharmacologic effects of montelukast.

DATA EXTRACTION

Information on the safety and efficacy of montelukast was evaluated on the basis of patient selection, study design, methodology, and statistical significance as compared with placebo or inhaled corticosteroid treatment.

DATA SYNTHESIS

Montelukast is approved for the prophylaxis and chronic treatment of asthma at a dose of 10 mg once daily for adolescents (> or =15 y) and adults and 5 mg once daily for children (6-14 y). In placebo-controlled clinical trials, montelukast significantly improved pulmonary lung function (as measured by forced expiratory volume in 1 sec), significantly reduced beta2-agonist use, and significantly improved patient-reported end points in adults and children (> or =6 y) with chronic asthma. In adults, a similar magnitude of improvement in lung function is seen with or without inhaled corticosteroid use; the effects of montelukast may be additive to those of inhaled corticosteroids and permit the reduction of the required dose of inhaled corticosteroids. In cases of exercise-induced asthma (adults and children), montelukast treatment attenuates the fall in pulmonary function following exercise. It attenuates both the early- and late-phase responses of asthma after allergen inhalation. Improvements in asthma control are similar in asthmatic patients who are aspirin-sensitive or not aspirin-sensitive and can be seen within one day of treatment. Tolerance does not develop, and the adverse events do not differ from those of placebo.

CONCLUSIONS

Montelukast is indicated for the prophylaxis of chronic asthma in adults and children (> or =6 y). It may be considered for use as first-line therapy in patients with mild persistent asthma or for additional control in patients who are still symptomatic while receiving treatment with inhaled corticosteroids. It may also be used for additional control in aspirin-sensitive asthmatic patients. Consideration may be given for using montelukast to allow tapering of the dose of inhaled corticosteroids while maintaining clinical stability. Chronic treatment with montelukast can provide additional control of symptoms during exercise, but inhaled beta2-agonists remain first-line therapy for prophylaxis and treatment.

Effects of food on clinical pharmacokinetics

Food-drug interactions can be associated with alterations in the pharmacokinetic and pharmacodynamic profile of various drugs that may have clinical implications. The various phases in which food may interact with a coadministered drug are: (i) before and during gastrointestinal absorption; (ii) during distribution; (iii) during metabolism; and (iv) during elimination. Absorption and metabolism are the phases where food has most effect, and this review will focus on those areas. It will also review the variable and complex effects of antacids and metal ions on drug absorption. Mechanisms related to food effects on drug absorption have been described under 5 categories: those causing decreased, delayed, increased or accelerated absorption, and those in which food has no significant effect. Among the major variables that interface between differential effects of food and postprandial bioavailability are: (i) the physicochemical characteristics and enantiomorphic composition of the drug; (ii) timing of meals in relation to time of drug administration; (iii) size and composition of meals (especially fat, protein and fibre); and (iv) dose size. However, the influence of food is largely a matter of the design of the pharmaceutical formulation. In addition, the mechanism of 'food effect' may involve physiological and sensory responses to food, such as changes in gastrointestinal milieu and gastric emptying rate, reflex action, and may also involve the site and route (either portal or lymphatic) of drug absorption. Mixing drugs with fruit juice, such as grapefruit and orange juice, and acidic beverages, such as commercial soft drinks, may affect absorption because of decreases in gastric pH, which could offer a therapeutic advantage in certain clinical conditions, such as patients with HIV disease and cancer. The increased bioavailability caused by the concomitant intake of grapefruit juice results from the inhibition of intestinal cytochrome P450(CYP)3A4, but not hepatic CYP3A4 or colon CYP3A5, which probably involves the bioflavonoid naringenin and furanocoumarins. Although there is a vast amount of literature, there is still no rational scientific basis to predict the effect of food for a particular chemical entity or a chemical class of therapeutic agents. A mechanistic understanding of the effects of food may serve as a key to the pharmacokinetic optimisation of patient therapy, both in outpatients and hospitalised patients of various age groups.

Montelukast dose selection in 6- to 14-year-olds: comparison of single-dose pharmacokinetics in children and adults

Montelukast, an oral leukotriene-receptor antagonist, has demonstrated efficacy and tolerability for the treatment of chronic asthma in adults. A once-daily 10 mg dose (film-coated tablet) was selected as the optimal adult dose based on dose-ranging studies. Asthma is a similar disease and is treated with the same medications in children and adults. These observations suggested that a dose of montelukast in children providing overall drug exposure (i.e., montelukast plasma concentrations) similar to that of the 10 mg film-coated tablet dose in adults would be efficacious, well tolerated, and obviate the need for separate dose-ranging studies in children. Therefore, the dose of montelukast for 6- to 14-year-old children was selected by identifying the chewable tablet dose of montelukast yielding a single-dose area under the plasma concentration-time curve (AUC) comparable to that achieved with the adult 10 mg film-coated tablet dose. Based on this approach, which included dose normalization of data from several pediatric pharmacokinetic studies, a 5 mg chewable tablet dose of montelukast was selected for use in clinical efficacy studies in 6- to 14-year-old children with asthma.

New perspectives for asthma treatment: anti-leukotriene drugs

Leukotrienes are synthesized by different cells, including eosinophils, neutrophils, basophils, lymphocytes, macrophages, and mast cells. Cysteinyl leukotrienes (LTC4, LTD4, and LTE4) are the most important leukotrienes in the pathogenesis of asthma. Pharmacologically, there are two different ways of blocking the action of leukotrienes: inhibiting their production by blocking 5-lipoxygenase or its activating protein, 5-lipoxygenase-activating protein (FLAP), (inhibitors) or by blocking their receptors (antagonists). The available antagonists are, for the moment, directed against the one receptor demonstrated to play a role in asthma symptoms, CysLT1, and they act in a competitive way. The only marketed 5-lipoxygenase inhibitor is zileuton (Zyflo). CysLT1 antagonists, currently on the pharmaceutical market in some countries, are zafirlukast (Accolate), pranlukast (Ultair, Onon), and montelukast (Singulair). Undoubtedly, drugs acting on leukotrienes constitute a new pharmacologic class in the therapeutic armamentarium for the management of asthma. From the pediatric point of view, montelukast is currently the most interesting drug of the group to date because of published trials in patients as young as 6 yr of age. At present, zafirlukast is only approved for use in patients 12 yr of age and older, although we understand that applications are likely to extend the age range into childhood shortly. However, more experience is necessary to establish a definite place for both leukotrienes in the step-by-step asthma treatment. New comparative studies (with sodium cromoglycate and inhaled steroids), which will probably be published in the near future, as well as studies on the use of montelukast in the treatment of children under 6 yr of age will add crucial information to our knowledge, and help to identify an appropriate use in the therapeutic algorithm. Montelukast will not be a substitute for inhaled corticosteroids or beta-agonists, although it may act as a 'sparing drug' (which might help tapering of steroids in some instances). Its role in exercise-induced asthma seems promising. Although its more widespread use could highlight low-frequency adverse effects, its apparent excellent tolerability is an additional advantage for the drug. Patients' preference for a twice-daily dosage over the inhaled medication, resulting in a better compliance, is relatively well established, at least for zafirlukast in adults, and these findings can probably be extended to montelukast, which only requires once-daily dosing in children.

The effect of montelukast (MK-0476), a cysteinyl leukotriene receptor antagonist, on allergen-induced airway responses and sputum cell counts in asthma

BACKGROUND

Cysteinyl leukotrienes are capable of inducing chemotaxis of eosinophils in vitro and within the airways of animals and humans in vivo.

OBJECTIVE

We hypothesized that montelukast (MK-0476), a potent cysLT1 receptor antagonist, would protect against allergen-induced early (EAR) and late (LAR) asthmatic responses by virtue of anti-inflammatory properties. Hence, we studied the effect of pretreatment with oral montelukast on allergen-induced airway responses. As an exploratory endpoint, changes in inflammatory cell differentials and eosinophil cationic protein (ECP) were evaluated in hypertonic saline-induced sputum.

METHODS

Twelve asthmatic men (20-34 years, FEV1 79-109% predicted, histamine PC20FEV1 <4 mg/mL) with dual responses to inhaled house dust mite extract participated in a two-period, double-blind, placebo-controlled, crossover study. Three oral doses of montelukast (10 mg) or matching placebo were administered 36 and 12 h before, and 12 h post-allergen. The airway response to allergen was measured by FEV1, and the EAR and LAR were expressed as the corresponding areas under the time-response curves (AUC0-3 h and AUC3-8h, respectively). During each study period, sputum was induced with 4.5% NaCl 24 h before and 24 h after a standardized allergen challenge. Processed whole sputum cytospins were stained with Giemsa, and cell counts expressed as percentage nonsquamous cells. ECP was measured by FEIA in sputum supernatants.

RESULTS

All subjects completed the study. The changes in baseline FEV1 were not significantly different between the two pretreatments (P = 0.183). Montelukast significantly inhibited the EAR and LAR, reducing the AUC0-3h by 75.4% (P<0.001) and the AUC3-8h by 56.9% (P = 0.003) as compared with placebo. Sputa of nine subjects could be included in the analysis (<80% squamous cells). Allergen challenge significantly increased sputum eosinophils after placebo (mean change +/- SD: 4.8 +/- 5.8%, P = 0.038), with a similar trend after montelukast (mean change +/- SD: 4.1 +/- 5.4%; P = 0.056). The allergen-induced changes in sputum eosinophils and ECP, however, were not significantly different between the two pretreatments (P = 0.652 and P = 0.506, respectively).

CONCLUSION

We conclude that oral montelukast protects against allergen-induced early and late airway responses in asthma. However, using the present dosing and sample size, this protection was not accompanied with changes in sputum eosinophil percentage or activity, which may require more prolonged pretreatment with cysLT1 receptor antagonists.

N-carbamoyl analogs of Zafirlukast: potent receptor antagonists of leukotriene D4

Exploration of the indole nitrogen region of Zafirlukast (1) has uncovered a potent series of cysteinyl leukotriene D4 (LTD4) antagonists. These studies showed that a variety of functionality could be incorporated in this region of the molecule without sacrificing potency. Efforts to exploit this site in order to improve oral efficacy are discussed.

Determination of montelukast sodium in human plasma by column-switching high-performance liquid chromatography with fluorescence detection

MK-0476 (montelukast sodium) is a potent and selective cysteinyl leukotriene receptor antagonist that is being investigated in the treatment of asthma. A simple and sensitive method for the determination of MK-0476 in human plasma was developed using column-switching high-performance liquid chromatography (HPLC) with fluorescence detection. A plasma sample was injected directly onto the HPLC system consisting of a pre-column (Capcell pak MF) and an analytical column (Capcell pak C18) which were connected with a six-port switching valve. The column eluate was monitored with a fluorescence detector (excitation at 350 nm; emission at 400 nm). The calibration curve was linear in a concentration range of 1-500 ng ml(-1) for MK-0476 in human plasma. The intra-day coefficients of variation of all concentrations within the range was less than 9.2%, and the intra-day accuracy values were between 97.2 and 114.6%. This method was used to measure the plasma concentration of MK-0476 following oral administration of the drug in humans.

Montelukast

Montelukast is a selective antagonist of the leukotriene D4 (LTD4) receptor. In patients with asthma, montelukast 5 to 250 mg/day attenuated LTD4-induced bronchoconstriction and, at a dosage of 10 mg, significantly reduced early and late airway response to allergen (dust mite extract) relative to placebo. In studies evaluating the effects of various dosages of montelukast on exercise-induced bronchoconstriction the optimal dose of the drug was found to be 10 mg. Montelukast 10 mg/day controlled asthma significantly more effectively than placebo in a 3-month randomised double-blind study. In a 9-month open extension of this trial, during which patients were randomised to treatment with montelukast 10 mg/day or beclomethasone (approximately 400 micrograms/day), daytime symptom score and beta-agonist use decreased to a similar extent in each group. In a further study, treatment with montelukast 10 mg/day permitted clinically significant tapering of corticosteroid dosage in patients with stable asthma. Montelukast (5 mg/day) has also demonstrated efficacy in childhood asthma. The tolerability profile of montelukast was similar to that of placebo in placebo-controlled clinical trials in adults and children; the most common adverse event was headache.

A novel photoaffinity probe for the LTD4 receptor

A novel photoaffinity probe for the leukotriene D4 receptor (LTD4) is described. L-745310, which is structurally related to the potent LTD4 antagonist MK-0476 (Singulair), was found to selectively label a 43-kDa protein in guinea-pig lung membrane previously identified as the LTD4 receptor.

Dose-related protection of exercise bronchoconstriction by montelukast, a cysteinyl leukotriene-receptor antagonist, at the end of a once-daily dosing interval

The dose-related protective effects of montelukast, a potent and selective cysteinyl leukotriene-receptor antagonist, against exercise-induced bronchoconstriction were investigated in a five-period, randomized, incomplete-block, crossover study with montelukast (0.4, 2, 10, 50 mg) and placebo. The study subjects were 27 nonsmoking, healthy stable patients with asthma (mean forced expiratory volume in 1 second [FEV1], 82.0% predicted) who demonstrated a > or = 20% decrease in FEV1 while beta-agonist was withheld for 6 hours before treadmill exercise. The standard exercise challenge was performed 20 to 24 hours, and again 32 to 36 hours, after the second of two once-daily doses. The effect of oral montelukast on exercise was measured by the area above the postexercise percentage decrease in FEV1 versus time curve from 0 to 60 minutes [AUC(0-60)], the maximal percentage decrease in FEV1 after exercise, and time after maximal decrease to recovery of FEV1 to within 5% of the preexercise baseline. Twenty to 24 hours after administration, montelukast caused dose-related protection, while providing similar protection against exercise-induced bronchoconstriction at the two highest doses. The AUC(0-60) values (mean +/- SD) were 637 +/- 898, 715 +/- 870, 988 +/- 1147, and 927 +/- 968 min. % for 50, 10, 2, and 0.4 mg montelukast, respectively, and 1193 +/- 1097 min. % for placebo (p = 0.003). No important clinical effect was present 36 hours after dosing. Montelukast was generally well tolerated at all dose levels. In conclusion, montelukast caused dose-related protection against exercise-induced bronchoconstriction at the end of a once-daily dosing interval. Protection against exercise-induced bronchoconstriction can be used to determine appropriate dose selection.

Montelukast causes prolonged, potent leukotriene D4-receptor antagonism in the airways of patients with asthma

Montelukast, a new specific oral cysteinyl LT3-receptor antagonist was evaluated for its activity in attenuating inhaled leukotriene D4 (LTD4) bronchoconstriction in patients with asthma. In two double-blind, placebo-controlled, randomized crossover studies, patients with mild asthma (forced expiratory volume in 1 second [FEV1] > or = 70%) were studied. In trial A, LTD4 challenge began 4 hours (peak plasma concentration) after a single dose of placebo or 5, 20, 100, and 250 mg montelukast. In trial B, and LTD4 challenge was started 20 hours after administration of placebo, 40 mg montelukast, or 200 mg montelukast. During each challenge, twofold increasing concentrations of LTD4 were inhaled until specific airways conductance (sGaw) decreased by at least 50% (PC50) or the highest concentration of LTD4 was inhaled. In trial A with all doses and in trial B with the 200 mg dose, bronchoconstriction was attenuated (50% fall in sGaw was not observed) up to the highest dose of LTD4 administered. In trial B, during the 40 mg period, only two of six patients exhibited a 50% fall in sGaw; PC50 ratios (montelukast 40 mg/placebo) were 18 and 45 in these two patients. These results indicate that montelukast is a highly potent and long-lasting antagonist of LTD4-induced bronchoconstriction in patients with asthma.

Pharmacokinetics, bioavailability, and safety of montelukast sodium (MK-0476) in healthy males and females

PURPOSE

The safety, tolerability, and pharmacokinetics of intravenous *i.v.) montelukast sodium (Singulair, MK-0476), and the oral bioavailability of montelukast sodium in healthy males and healthy females were studied.

METHODS

This was a two-part study. Part I was a four-period study in males of rising i.v. doses of montelukast sodium (3, 9, and 18 mg) administered as 15-minute constant-rate i.v. infusions (Periods 1-3), followed by a 10-mg oral tablet dose of montelukast sodium (Period 4) under fasting conditions. Part II was a four-period study in females of i.v. montelukast sodium (9 mg) infused over 15 and 5 minutes (Periods 5 and 6, respectively) or injected as a bolus over 2 minutes (Period 7), followed by a 10-mg oral tablet dose of montelukast sodium (Period 8). Plasma samples were collected and analyzed by HPLC.

RESULTS

In males (N = 6), as the i.v. dose of montelukast sodium increased from 3 to 18 mg, the area under the plasma concentration-time curve of montelukast sodium from time 0 to infinity (AUC) increased proportionately. The mean values of plasma clearance (CL), steady-state volume of distribution (Vss), plasma terminal half-life (t1/12), and mean residence time in the body (MRTi.v.) of montelukast sodium were 45.5 ml/min, 10.5 1, 5.1 hr, and 3.9 hr, respectively, and remained essentially constant over the i.v. dosage range. Following oral administration of a 10-mg tablet of montelukast sodium, the AUC, maximum plasma concentration (Cmax), time when Cmax occurred (Tmax), apparent t1/12, mean absorption time (MAT), and bioavailability (F) of montelukast sodium averaged 2441 ng.hr/ml, 385 ng/ml. 3.7 hr, 4.9 hr, 3.4 hr, and 66%, respectively. Following i.v. administration of 9 mg of montelukast sodium to females (N = 6), the values of CL, Vss, t1/2, and MRT i.v. averaged 47.6 ml/min, 9.6 1, 4.5 hr, and 3.6 hr, respectively. Following oral administration of a 10-mg tablet to females, the mean AUC, Cmax, Tmax, apparent t1/2, MAT and F were 2270 ng.hr/ml, 350 ng/ml, 3.3 hr, 4.4 hr, 2.6 hr, and 58%, respectively. These parameter values were similar to or slightly smaller than those in healthy males receiving the same i.v. and oral doses.

CONCLUSIONS

The disposition kinetics of montelukast sodium were linear. Gender had little or no effect on the kinetics of montelukast sodium. Safety results from this study indicate that intravenous doses of montelukast sodium from 3 to 18 mg and a 10-mg oral dose are well tolerated.