What is the literature on a therapeutic interchange for zafirlukast to montelukast for adult patients?

Please summarize literature on a therapeutic interchange for zafirlukast to montelukast for adult patients.

Comment by InpharmD Researcher

Literature directly evaluating a therapeutic interchange from zafirlukast to montelukast in adult patients is limited, but current 2026 Global Initiative for Asthma (GINA) guidelines for asthma management and prevention do not recommend one leukotriene receptor antagonist over another. Available evidence suggests that montelukast and zafirlukast have generally comparable efficacy and safety profiles, although some indirect analyses have reported a potential advantage for montelukast in reducing asthma exacerbations and treatment discontinuations.

Background

Per the 2026 Global Initiative for Asthma (GINA) guidelines for asthma management and prevention, leukotriene receptor antagonists (LTRAs), such as montelukast, zafirlukast and zileuton, are reportedly less effective than inhaled corticosteroids (ICS) in treatment of exacerbations. Still, these medications have been previously studied and may be utilized as alternative therapies in adults and adolescents in Step 1 or 2; may be combined with a low-dose ICS for Step 3; or may be added to a medium- or high-dose ICS in Step 4. No suggestion for one LTRA over another was provided within guidance. [1]

A 2012 Cochrane systematic review examined LTRA agents compared to inhaled corticosteroids in adults and children with persistent asthma, and included both zafirlukast (20 mg twice daily) and montelukast (10 mg once daily) as the test interventions across 56 trials. In the subgroup analysis stratified by anti-leukotriene agent, there was no statistically significant difference between montelukast and zafirlukast in the primary outcome of exacerbations requiring systemic corticosteroids (montelukast RR 1.55, 95% CI 1.14-2.12 vs. zafirlukast RR 1.92, 95% CI 0.88-4.20; p = 0.62), suggesting comparable efficacy between the two agents within the LTRA class. Both agents similarly demonstrated inferior efficacy compared to inhaled corticosteroids across secondary outcomes including FEV₁ improvement, symptom control, rescue β₂-agonist use, and quality of life in adult patients. The overall adverse effect profile was not significantly different between anti-leukotriene agents as a class and inhaled corticosteroids, and no distinction in safety between zafirlukast and montelukast was identified in the review. Overall, the two agents are noted to have equivalent mechanism of action, comparable efficacy outcomes, and similar tolerability profiles. [2]

Conversely, a previous 2009 meta-analysis found slightly conflicting results when comparing the relative efficacy and safety of montelukast (MON) and zafirlukast (ZAF) for treatment of chronic bronchial asthma in adults. The study analyzed data from four different comparisons: LTRA versus inhaled corticosteroids, LTRA versus placebo, LTRA as an add-on to inhaled corticosteroids, and LTRA as an add-on to long-acting beta agonists. When comparing MON to ZAF, the relative risk of asthma exacerbations was considerably reduced, with a combined estimate indicating a 38% reduction in risk. This determination was based on substantial data sets comprising 9,624 and 2,323 patients for MON and ZAF, respectively. Furthermore, MON demonstrated advantages in several safety outcomes; the relative risk of overall withdrawals was 0.61, and withdrawals due to poor control were 0.44, while withdrawals due to adverse events and liver enzyme elevations showed RRs of 0.75 and 0.43, respectively. The overall adverse events incidence was nearly equivalent between the two drugs, with an RR of 0.95. These findings suggest that MON may offer superior efficacy in preventing asthma exacerbations with fewer withdrawal incidences compared to ZAF, positioning it as a potentially more effective therapeutic option in this patient population. [3]

Literature Review

A search of the published medical literature revealed 2 studies investigating the researchable question:

Please summarize literature on a therapeutic interchange for zafirlukast to montelukast for adult patients.

Level of evidence

C - Multiple studies with limitations or conflicting results Read more→

Please see Tables 1-2 for your response.

Recommended dosages in various clinical scenarios
Indication	Population	Montelukast	Zafirlukast
Asthma	Adult and adolescent patients 15 years of age and older	one 10 mg tablet	20 mg twice daily
	Pediatric patients 6 to 14 years of age	one 5 mg chewable tablet	12+ years old: 20 mg twice daily 5-11 years old: 10 mg twice daily
	Pediatric patients 2 to 5 years of age	one 4 mg chewable tablet or one packet of oral granules	-
	Pediatric patients 12 to 23 months of age*	one packet 4 mg oral granules	-
Note: only montelukast is indicated for exercise-induced bronchoconstriction, allergic rhinitis, and perennial allergic rhinitis. * Safety and effectiveness in pediatric patients less than 12 months of age with asthma have not been established.

References:
[1] [1] Singulair (montelukast granule, tablet, chewable tablet). Prescribing information. Organon LLC; 2025.
[2] [2] Zafirlukast tablet. Prescribing information. Strides Pharma Science Limited; 2026.

Effect of the Two Different Leukotriene Receptor Antagonists, Montelukast and Zafirlukast, on Quality of Life: A 12-week Randomized Study
Design	Randomized study N= 40
Objective	To compare the effectiveness of the leukotriene receptor antagonists montelukast and zafirlukast on quality of life in mild asthmatic patients
Study Groups	Montelukast group (n= 20) Zafirlukast group (n= 20)
Inclusion Criteria	Mild asthmatic patients
Exclusion Criteria	Not specified
Methods	Patients were randomized into two groups: one treated with montelukast (10 mg daily) and the other with zafirlukast (40 mg daily) for 12 weeks. Clinical examinations, spirometry, and the Asthma Quality of Life Questionnaire were used to assess outcomes. Scores ranged from 1 (maximal impairment) to 7 (no impairment).
Duration	12 weeks
Outcome Measures	Improvement in quality of life scores across various domains (physical activities, symptoms, emotions, environmental stimuli)
Baseline Characteristics		Montelukast group (n= 20)	Zafirlukast group (n= 20)
	Baseline median value for all items	4.7	4.8
	Physical activities mean value	5.1	5.0
	Symptoms median score	5.0	4.9
	Emotions median score	4.7	4.8
	Environmental stimuli mean value	4.6	4.7
Results		Montelukast group (n= 20)	Zafirlukast group (n= 20)	p-value
	All items post-treatment median value	5.5	5.7	<0.05
	Physical activities post-treatment mean value	5.9	5.7	<0.05
	Symptoms post-treatment median score	5.7	5.6	<0.05
	Emotions post-treatment median score	5.3	5.8	<0.05
	Environmental stimuli post-treatment mean value	5.3	5.6	<0.05
Adverse Events	Not specified
Study Author Conclusions	Both montelukast and zafirlukast significantly improved quality of life in mild asthmatic patients, with no significant differences between the two treatments.
Critique	The study provides valuable insights into the effectiveness of leukotriene receptor antagonists on quality of life in asthmatic patients. However, the small sample size and lack of detailed adverse event reporting may limit the generalizability of the findings. Additionally, the study did not compare these treatments with inhaled corticosteroids, which are considered the preferred option for asthma management.

References:
[1] [1] Riccioni G, Vecchia RD, Ilio CD, DOrazio N. Effect of the Two Different Leukotriene Receptor Antagonists, Montelukast and Zafirlukast, on Quality of Life. Providence. 2004;25(6):445-8.