Is montelukast (Singulair) safe to use during pregnancy?

Montelukast Safety During Pregnancy

Montelukast can be safely used during pregnancy, particularly for women with recalcitrant asthma who have shown a favorable response prior to pregnancy. 1

Evidence for Safety

Montelukast is classified as a Pregnancy Category B medication, which means:

• Animal reproduction studies have not demonstrated risk to the fetus
• There are no adequate well-controlled studies in pregnant women 2
• It is not teratogenic in animal studies 1, 2

The safety profile is supported by several key findings:

• A prospective, comparative study of 180 montelukast-exposed pregnancies found no increased rate of major malformations above the baseline risk 3
• A more recent two-center cohort study in Japan showed that montelukast was not associated with increased risk of major congenital anomalies (adjusted odds ratio 0.78) 4
• The American Congress of Obstetricians and Gynecologists and the American College of Allergy recommend montelukast for recalcitrant asthma during pregnancy when patients have shown favorable response before pregnancy 1

Clinical Decision Algorithm

1. For asthma management:

   • Montelukast can be continued or initiated for recalcitrant asthma during pregnancy, especially in women with prior positive response 1
   • Inhaled corticosteroids (particularly budesonide) should be considered as first-line therapy before montelukast 5

2. For allergic rhinitis:

   • Montelukast is considered safe for allergic rhinitis during pregnancy 1
   • However, intranasal corticosteroids may be preferred as first-line therapy 1

3. For chronic rhinosinusitis (CRS):

   • Expert panels recommend avoiding anti-leukotrienes for CRS maintenance during pregnancy 1
   • Saline nasal rinses and topical corticosteroid nasal sprays are preferred maintenance therapy for CRS 1

Important Considerations

Breastfeeding

• Montelukast is excreted in breast milk (about 1% of the drug passes into breast milk)
• The extensive metabolism and plasma protein binding are thought to limit exposure
• Benefits of breastfeeding generally outweigh the risk of exposure 1
• Consider breastfeeding prior to medication intake to further limit exposure 1

Monitoring

• The manufacturer maintains a registry for patients exposed to montelukast during pregnancy 2
• Healthcare providers are encouraged to report prenatal exposure to the Pregnancy Registry 2

Potential Concerns

• A study noted lower birth weight in montelukast-exposed infants compared to controls, but this was likely associated with the severity of maternal asthma rather than the medication itself 3
• During worldwide marketing experience, congenital limb defects have been rarely reported in offspring of women taking montelukast during pregnancy, but most were also taking other asthma medications and a causal relationship has not been established 2

Conclusion

When weighing risks versus benefits, the evidence strongly supports that montelukast can be safely used during pregnancy, particularly for asthma management in women who have previously responded well to the medication. For chronic rhinosinusitis, other treatment options should be considered first. The medication's Pregnancy Category B classification and multiple reassuring studies provide confidence in its safety profile for pregnant women who need this therapy.