Montelukast for persistent asthma

Influence of leukotriene pathway polymorphisms on response to montelukast in asthma

RATIONALE

Interpatient variability in montelukast response may be related to variation in leukotriene pathway candidate genes.

OBJECTIVE

To determine associations between polymorphisms in leukotriene pathway candidate genes with outcomes in patients with asthma receiving montelukast for 6 mo who participated in a clinical trial.

METHODS

Polymorphisms were typed using Sequenom matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass array spectrometry and published methods; haplotypes were imputed using single nucleotide polymorphism-expectation maximization (SNP-EM). Analysis of variance and logistic regression models were used to test for changes in outcomes by genotype. In addition, chi(2) and likelihood ratio tests were used to test for differences between groups. Case-control comparisons were analyzed using the SNP-EM Omnibus likelihood ratio test.

MEASUREMENTS

Outcomes were asthma exacerbation rate and changes in FEV(1) compared with baseline.

RESULTS

DNA was collected from 252 participants: 69% were white, 26% were African American. Twenty-eight SNPs in the ALOX5, LTA4H, LTC4S, MRP1, and cysLT1R genes, and an ALOX5 repeat polymorphism were successfully typed. There were racial disparities in allele frequencies in 17 SNPs and in the repeat polymorphism. Association analyses were performed in 61 whites. Associations were found between genotypes of SNPs in the ALOX5 (rs2115819) and MRP1 (rs119774) genes and changes in FEV(1) (p < 0.05), and between two SNPs in LTC4S (rs730012) and in LTA4H (rs2660845) genes for exacerbation rates. Mutant ALOX5 repeat polymorphism was associated with decreased exacerbation rates. There was strong linkage disequilibrium between ALOX5 SNPs. Associations between ALOX5 haplotypes and risk of exacerbations were found.

CONCLUSIONS

Genetic variation in leukotriene pathway candidate genes contributes to variability in montelukast response.

Aspirin intolerance and the cyclooxygenase-leukotriene pathways

PURPOSE OF REVIEW

In up to 10% of patients with bronchial asthma, aspirin and other nonsteroidal antiinflammatory drugs precipitate asthmatic attacks. This is a hallmark of a distinct clinical syndrome that develops according to a characteristic sequence of symptoms. Here we discuss its clinical picture and management as related to the abnormalities in arachidonic acid transformations.

RECENT FINDINGS

At the biochemical level, the characteristic feature is profound alteration in eicosanoid biosynthesis and metabolism. Major advances in the molecular biology of eicosanoids, exemplified by the cloning of cysteinyl-leukotriene receptors and discovery of a whole family of cyclooxygenase enzymes, offer new insights into mechanisms operating in aspirin-induced asthma. Clinical interest has been enhanced by the introduction into therapy of highly specific cyclooxygenase-2 inhibitors and antileukotriene drugs.

SUMMARY

Recent studies have improved our understanding of mechanisms operating in asthma and unvieled the role of eicosanoid mediators in pulmonary disease.

Aspirin-induced asthma: advances in pathogenesis, diagnosis, and management

In some asthmatic individuals, aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) that inhibit cyclooxygen-ase 1 (COX-1) exacerbate the condition. This distinct clinical syndrome, called aspirin-induced asthma (AIA), is characterized by an eosinophilic rhinosinusitis, nasal polyposis, aspirin sensitivity, and asthma. There is no in vitro test for the disorder, and diagnosis can be established only by provocation challenges with aspirin or NSAIDs. Recent major advances in the molecular biology of eicosanoids, exemplified by the cloning of 2 cysteinyl leukotriene receptors and the discovery of a whole family of cyclooxygenase enzymes, offer new insights into mechanisms operating in AIA. The disease runs a protracted course even if COX-1 inhibitors are avoided, and the course is often severe, many patients requiring systemic corticosteroids to control their sinusitis and asthma. Aspirin and NSAIDs should be avoided, but highly specific COX-2 inhibitors, known as coxibs, are well tolerated and can be safely used. Aspirin desensitization, followed by daily aspirin treatment, is a valuable therapeutic option in most patients with AIA, particularly those with recurrent nasal polyposis or overdependence on systemic corticosteroids.

Protection against exercise-induced bronchoconstriction by montelukast in aspirin-sensitive and aspirin-tolerant patients with asthma

BACKGROUND

Montelukast, a cysteinyl-leukotriene receptor antagonist, was reported to have a protective effect against exercise-induced bronchoconstriction (EIB). Aspirin-induced asthma (AIA) is characterized by overproduction of cysteinyl-leukotrienes.

OBJECTIVE

The aim of the study was to compare the response to exercise and the effect of montelukast on EIB in AIA as compared to aspirin-tolerant asthma (ATA).

METHODS

A placebo-controlled, double blind, cross-over randomized study was performed in 19 AIA and 21 ATA patients with stable asthma. A single dose of montelukast (10 mg) or placebo (PL), was given orally one hour prior to exercise challenge. FEV1 was measured before and 5, 10, 15 min after exercise and then at 15-minute intervals for 4 h. Urinary LTE4 excretion and blood eosinophil count were measured at baseline, 2 h and 4 h following exercise challenge.

RESULTS

Positive bronchial response to exercise was observed in 47.5% of all patients studied. Exercise led to almost identical maximal fall in FEV1 in AIA and ATA patients (23.5% +/- 6.8% vs. 21.8% +/- 12.0%, respectively; P = 0.7). Montelukast, as compared to PL, significantly attenuated EIB in 63.2% of 19 patients with positive exercise test preceded by PL. The mean of maximum fall in FEV1 from the pre-exercise value was 10.2% +/- 13.8 after montelukast as compared to 22.5% +/- 10.2 after placebo (P < 0.001). No significant differences between protective effect of montelukast was observed in AIA as compared to ATA patients (P = 0.63, anova). Urinary LTE4 excretion showed no change following exercise, irrespective of the result of the test in all subjects.

CONCLUSION

Patients with AIA and ATA react similarly to exercise challenge and obtain similar protection against EIB by montelukast.

The role of antileukotrienes in the treatment of asthma

Cysteinyl leukotrienes (Cys-LTs) are mediators released in asthma and are both direct bronchoconstrictors and proinflammatory substances that mediated several steps in the pathophysiology of chronic asthma, including inflammatory cells recruitment, vascular leakage, and possibly airway remodelling. Available evidence from clinical trials and real world experience derived from managing patients with asthma justifies a broader role for antiLTRAs in asthma management than that recommended in the National Asthma Education and Prevention Programm (NAEPP) and National Health Lung and Blood Institute (NHLBI) treatment guidelines. Leukotriene-receptor antagonist drugs (LTRAs) seem to be effective alternatives to inhaled corticosteroids (ICS) either as monotherapy or as adjunctive therapy that reduces the need for higher doses of ICS in patients with mild-to-moderate persistent asthma. LTRAs may be used as adjunctive therapy for al levels of disease severity because they are effective in combination with ICS during long-term maintenance therapy. The agents seem especially effective in preventing aspirin-induced asthma, exercise-induced asthma (EIA) and they may provide an additional advantage of reducing nasal congestion in patients with both asthma and rhinitis.

Analgesics and asthma

The incidence of asthma is increasing throughout the world, which presents both public health and economic concerns. It is widely recognized that in some adult patients with asthma, aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) that inhibit cyclooxygenase (COX)-1 exacerbate the condition. This is a distinct clinical syndrome called aspirin-induced asthma (AIA). The disease develops according to a characteristic pattern of symptoms. Persistent eosinophilic rhinosinusitis precedes development of nasal polyposis, aspirin hypersensitivity, and asthma. There is no in vitro test, and diagnosis can only be established by provocation tests with aspirin. At the biochemical level, AIA is characterized by a chronic overproduction of cysteinyl leukotrienes. The key enzyme, leukotriene C4 synthase, is overexpressed in bronchi, and its messenger RNA is upregulated in peripheral blood eosinophils. This can be partly related to the genetic polymorphism of the enzyme. The disease runs a protracted course, even if COX-1 inhibitors are avoided. The course of AIA is often severe, and at least half of the patients need systemic corticosteroids to control their asthma. To prevent life-threatening reactions, patients with AIA should avoid aspirin and other analgesics that inhibit COX-1. The incidence of cross-sensitivity to paracetamol in AIA patients is low and, when a reaction does occur, the symptoms experienced are shorter and milder than if the reactions were evoked by an NSAID. Rapidly growing evidence indicates that highly specific COX-2 inhibitors, known as coxibs, are well tolerated and can be safely used by AIA patients.