Is montelukast (Singulair) safe to use during pregnancy?

Is Montelukast Safe in Pregnancy?

Yes, montelukast is safe to use during pregnancy and can be continued or initiated for recalcitrant asthma, particularly in patients who have shown favorable response prior to pregnancy. 1, 2

FDA Classification and Safety Profile

• Montelukast is classified as FDA Pregnancy Category B, meaning animal studies have not demonstrated fetal risk, though controlled human studies are limited 3
• Multiple guidelines from the American Congress of Obstetricians and Gynecologists and the American College of Allergy support montelukast use in pregnancy when clinically indicated 2, 4
• The 2008 practice parameter from the Journal of Allergy and Clinical Immunology explicitly states: "Montelukast is a safe treatment for allergic rhinitis during pregnancy" 1

Evidence from Human Studies

• A 2009 multicentre prospective study of 180 montelukast-exposed pregnancies found no increase in the baseline rate of major malformations (1 major malformation out of 160 live births) 5
• A 2022 Japanese cohort study of 231 pregnant women exposed to leukotriene receptor antagonists showed a major congenital anomaly rate of only 1.9%, with no significant association between LTRA exposure and malformations (adjusted OR 0.78,95% CI 0.23-2.05) 6
• A 2017 Danish population study of 754,300 pregnancies found no significant increase in major congenital anomalies with montelukast exposure (adjusted OR 1.4,95% CI 0.9-2.3) 7

Clinical Recommendations by Indication

For Asthma Management

• Montelukast can be continued or initiated for recalcitrant asthma during pregnancy, especially when conventional inhaled medications fail to achieve adequate control 1, 2
• Inhaled corticosteroids (particularly budesonide) remain first-line therapy with decades of safety data 2
• Poorly controlled asthma poses greater risks to maternal and fetal health than medication use 2, 8

For Allergic Rhinitis

• While montelukast is safe, intranasal corticosteroids or sodium cromolyn may be preferred first-line options for allergic rhinitis during pregnancy 2, 4
• Montelukast is generally not recommended for chronic rhinosinusitis (CRS) maintenance during pregnancy due to lack of efficacy data in this condition 2

Breastfeeding Considerations

• Only about 1% of montelukast passes into breast milk, and extensive metabolism plus plasma protein binding limit infant exposure 2, 8
• The benefits of breastfeeding generally outweigh the risk of exposure 2, 4
• Consider breastfeeding prior to medication intake to further minimize infant exposure 2, 4

Important Caveats and Monitoring

• Post-marketing surveillance has reported rare cases of congenital limb defects in offspring of women taking montelukast during pregnancy, though a causal relationship has not been established 3
• Most women reporting these events were also taking other asthma medications 3
• The European Respiratory Society classifies montelukast as "probably safe" with limited data suggesting no significantly increased risk of malformations 2
• Regular monitoring of asthma control is essential during pregnancy 2, 8
• Use montelukast at the lowest effective dose during pregnancy 2

What to Avoid

• 5-lipoxygenase inhibitors (such as zileuton) should be avoided in both pregnant and lactating mothers 2
• Oral decongestants should be avoided during the first trimester 4
• First-generation antihistamines should be avoided given their sedative and anticholinergic properties 1, 4
• Aspirin therapy for aspirin-exacerbated respiratory disease should be discontinued during pregnancy 1

Common Pitfall

• Do not assume that uncontrolled asthma is safer than medication use—asthma exacerbations during pregnancy can lead to severe fetal problems and should be managed aggressively 2