Is Montelukast (Singulair) safe to use during pregnancy?

Montelukast Safety in Pregnancy

Montelukast can be safely used during pregnancy for asthma control, particularly when patients have demonstrated favorable response prior to conception or when conventional inhaled therapies are insufficient. 1

FDA Classification and Regulatory Status

• Montelukast is FDA Pregnancy Category B, meaning animal studies show no fetal risk but controlled human studies are limited 2, 3
• The FDA label notes that congenital limb defects have been rarely reported in post-marketing surveillance, though no causal relationship has been established 2
• A pregnancy registry is maintained to monitor outcomes; healthcare providers should report exposures by calling (800) 986-8999 2

Guideline-Based Recommendations

Major medical societies support montelukast use when clinically indicated:

• The American Congress of Obstetricians and Gynecologists and American College of Allergy support montelukast use during pregnancy 1
• The European Respiratory Society and Thoracic Society of Australia and New Zealand classify it as "probably safe" with limited data suggesting no significantly increased risk of malformations 1
• The 2004 NAEPP Expert Panel noted minimal human data available at that time, though animal studies submitted to FDA were reassuring 4

Clinical Context: When to Use Montelukast

Prioritize inhaled medications first, then add montelukast for recalcitrant asthma:

• Inhaled corticosteroids (especially budesonide) remain first-line therapy with decades of safety data 1
• Short-acting beta-agonists like albuterol have extensive reassuring pregnancy data 1
• Consider initiating or continuing montelukast when conventional inhaled medications fail to achieve adequate asthma control 1
• The risk of untreated severe asthma exceeds any theoretical medication risk 1

Evidence from Human Studies

Recent research provides reassuring safety data:

• A 2022 Japanese prospective cohort study of 231 pregnancies found no increased risk of major congenital anomalies (adjusted OR 0.78,95% CI 0.23-2.05) 5
• A 2017 Danish population study of 827 montelukast-exposed pregnancies found no significant increase in major congenital anomalies (adjusted OR 1.4,95% CI 0.9-2.3 for montelukast alone; OR 1.0,95% CI 0.6-1.8 for montelukast with other asthma medications) 6
• A 2009 multicentre study of 180 pregnancies reported only 1 major malformation among 160 live births, not exceeding the 1-3% baseline risk 7

Important Pregnancy-Related Findings

Maternal asthma severity, not montelukast, appears responsible for adverse outcomes:

• Lower birth weight (approximately 300g less) is associated with asthma severity rather than montelukast exposure specifically 7
• Increased rates of preterm birth, preeclampsia, and gestational diabetes are known complications of maternal asthma itself 6
• Fetal distress rates were higher in asthma patients but not specifically attributable to montelukast when analyzed by disease severity 7

Practical Management Algorithm

Follow this stepwise approach:

1. Assess asthma control - Poorly controlled asthma poses greater maternal and fetal risks than medication exposure 1
2. Optimize inhaled therapy first - Use budesonide and albuterol as preferred agents with most safety data 1
3. Add or continue montelukast if patient had good response pre-pregnancy or if inhaled therapy alone is insufficient 1
4. Use lowest effective dose throughout pregnancy 1
5. Monitor asthma control regularly - Adjust therapy to maintain optimal control 1

Critical Caveat

Avoid 5-lipoxygenase inhibitors (zileuton) - These should not be used in pregnant or lactating mothers, unlike leukotriene receptor antagonists like montelukast 1

Breastfeeding Considerations

• Only approximately 1% of montelukast passes into breast milk 1, 8
• Extensive metabolism and plasma protein binding limit infant exposure 1, 8
• Benefits of breastfeeding outweigh exposure risks 8
• Consider breastfeeding prior to medication intake to further minimize infant exposure 1