Can montelukast (Singulair) be prescribed to a woman who is 3 months pregnant with asthma?

Can Montelukast (Singulair) Be Given to a 3-Month Pregnant Woman?

Yes, montelukast can be safely prescribed to a woman at 3 months of pregnancy for asthma control, particularly when conventional inhaled medications fail to achieve adequate control or when she had a favorable response to montelukast before pregnancy. 1, 2, 3

Safety Classification and Evidence

• Montelukast is FDA Pregnancy Category B, meaning animal reproductive studies show no fetal risk, though adequate controlled human studies are limited. 2, 4, 5

• The European Respiratory Society/Thoracic Society of Australia and New Zealand classify montelukast as "possibly safe" during pregnancy, with limited data suggesting no significantly increased risk of malformations, though the number of exposed women remains insufficient to ensure complete fetal safety. 1

• Cases of limb reduction defects have been reported in post-marketing surveillance, but a causal relationship has not been established. 1, 5

• A large prospective study of 180 montelukast-exposed pregnancies found only 1 major malformation (0.6%), which does not exceed the 1-3% baseline risk in the general population. 6

• A Danish population study of 827 pregnancies exposed to montelukast found no increased risk of 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). 7

• A Japanese prospective cohort study of 231 LTRA-exposed pregnancies (including 122 montelukast exposures) found a major congenital anomaly rate of 1.9%, with no significant association between LTRA exposure and congenital anomalies (adjusted OR 0.78,95% CI 0.23-2.05). 8

Clinical Recommendations

When to Use Montelukast:

• Continue montelukast if it was providing good asthma control before pregnancy, as the American Congress of Obstetricians and Gynecologists and American College of Allergy support its use when clinically indicated. 2, 3

• Initiate montelukast for recalcitrant asthma when conventional inhaled medications fail to secure adequate asthma control. 1, 2, 3

• Use montelukast as second-line therapy after inhaled corticosteroids and short-acting beta-agonists. 1, 2

Treatment Algorithm for Asthma in Pregnancy

First-line therapy:

• Inhaled corticosteroids (preferably budesonide) have decades of safety data showing no adverse fetal effects. 2, 3
• Short-acting beta-agonists (albuterol/salbutamol) have extensive reassuring pregnancy data and are unlikely to cause structural anomalies. 1, 2, 3

Second-line therapy (when first-line fails):

• Add montelukast for inadequate asthma control despite optimal inhaled therapy. 1, 2, 3

Critical principle:

• Untreated or poorly controlled asthma poses greater risks to maternal and fetal health than appropriate medication use, including risks of perinatal mortality, pre-eclampsia, preterm birth, and low-birth-weight infants. 1, 3

Important Caveats and Monitoring

• Maternal hypoxia from severe asthma exacerbations has well-described adverse effects on the fetus, making aggressive asthma management essential. 1

• About 1% of montelukast passes into breast milk, but extensive metabolism and plasma protein binding limit infant exposure, making breastfeeding generally safe. 2, 4

• Montelukast crosses the placenta following oral dosing in animal studies. 5

• Regular monitoring of asthma control is essential during pregnancy, as asthma severity can change throughout gestation. 2, 3

• Use 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

• Montelukast is generally not recommended for chronic rhinosinusitis during pregnancy due to lack of efficacy data in this condition. 2