Are montelukast and levocetirizine teratogenic?

Safety of Montelukast and Levocetirizine During Pregnancy

Based on current evidence, montelukast is not teratogenic and is classified as FDA Pregnancy Category B, while levocetirizine has limited pregnancy data but other second-generation antihistamines like cetirizine and loratadine are considered safer options during pregnancy.

Montelukast Safety Profile

Montelukast has been extensively studied regarding its safety during pregnancy:

• Classified as FDA Pregnancy Category B, indicating no evidence of teratogenicity in animal studies 1
• The American Congress of Obstetricians and Gynecologists and American College of Allergy recommend montelukast could be considered in recalcitrant asthma during pregnancy, especially if the patient has shown favorable response prior to pregnancy 2
• No teratogenicity was observed in rats at oral doses up to 400 mg/kg/day and in rabbits at oral doses up to 300 mg/kg/day 1
• While rare reports of congenital limb defects have been reported during worldwide marketing experience, most women were also taking other asthma medications, and a causal relationship has not been established 1

Important considerations for montelukast:

• The manufacturer maintains a pregnancy registry to monitor outcomes of women exposed to montelukast during pregnancy 1
• Montelukast crosses the placenta following oral dosing in animal studies 1
• About 1% of the drug passes into breast milk, but the extensive metabolism and plasma protein binding are thought to limit exposure 2

Levocetirizine Safety Profile

Information on levocetirizine specifically during pregnancy is more limited:

• Has limited data available on use during pregnancy 3
• Second-generation antihistamines like cetirizine (the parent compound of levocetirizine) and loratadine are generally recommended as safer options during pregnancy 3
• The American College of Allergy, Asthma, and Immunology recommends second-generation antihistamines like cetirizine and loratadine as the safest options during pregnancy 3

Clinical Recommendations

For patients requiring treatment during pregnancy:

1. For asthma management:

   • Montelukast can be continued or initiated for recalcitrant asthma during pregnancy, especially in those with prior favorable response 2
   • Inhaled corticosteroids and beta agonists are preferred as first-line therapy for asthma during pregnancy 2

2. For allergic rhinitis management:

   • Second-generation antihistamines like cetirizine and loratadine are preferred over levocetirizine due to more established safety data 3
   • If antihistamine therapy is necessary, the first trimester is the most critical period for caution 3

3. Important precautions:

   • The first trimester is the most critical period for potential congenital malformations 3
   • Use the lowest effective dose for the shortest duration possible 3
   • Avoid 5-lipoxygenase inhibitors in both pregnant and lactating mothers 2

Breastfeeding Considerations

• Montelukast is excreted in breast milk, but the benefits of breastfeeding generally outweigh the risk of exposure 2
• Consider breastfeeding prior to medication intake to further limit exposure 2

Common Pitfalls to Avoid

1. Stopping asthma medications during pregnancy, which can lead to poor asthma control and increased risks to both mother and fetus
2. Using oral decongestants during pregnancy, especially in the first trimester, due to potential risks
3. Failing to monitor patients on montelukast for neuropsychiatric events, which can occur regardless of pregnancy status
4. Not considering the risk-benefit ratio when prescribing medications during pregnancy

Remember that poorly controlled asthma poses greater risks to the fetus (including neonatal hypoxia, intrauterine growth restriction, preterm birth, low birth weight, and fetal death) than the potential risks of most asthma medications 2.