Is the combined use of bilastine and montelukast safe during pregnancy?

Bilastine with Montelukast in Pregnancy

Montelukast can be used during pregnancy when needed for asthma control, but there is no safety data for bilastine in pregnancy—avoid bilastine and use established antihistamines instead.

Montelukast Safety Profile

The 2020 ERS/TSANZ guidelines classify montelukast as TGA Category B1/FDA Category B, indicating "possibly safe" status 1. The evidence shows:

• Limited data suggest no significantly increased risk of major malformations 1
• Cases of limb reduction defects have been reported, though causality remains unestablished 1
• The FDA label confirms no teratogenicity in animal studies at doses far exceeding human exposure, though congenital limb defects have been rarely reported during post-marketing surveillance 2

Recent Research Evidence

The most recent and highest-quality study is the 2026 AM-PREGNANT cohort (44,435 pregnancies), which found no association between first-trimester montelukast exposure and major congenital malformations 3. This aligns with:

• A 2022 Japanese prospective cohort (231 pregnancies): adjusted OR 0.78 for major anomalies (95% CI 0.23-2.05) 4
• A 2017 Danish population study (754,300 pregnancies): no increased risk of congenital anomalies, though higher rates of preterm birth and maternal complications were attributed to asthma severity 5

Clinical Recommendation for Montelukast

Use montelukast during pregnancy only when conventional asthma medications fail to secure control 1. The guideline explicitly states it should be reserved for second-line use when better-tested options are inadequate. For women already controlled on montelukast pre-pregnancy with demonstrated benefit, continuation can be considered 6.

Key Caveats:

• The increased risks of preterm birth, preeclampsia, and lower birth weight observed in some studies are likely attributable to maternal asthma severity rather than montelukast itself 5, 7
• Counsel patients about rare limb defects reported in post-marketing surveillance, though causality is unproven 2
• Monitor for neuropsychiatric events, as montelukast carries FDA warnings for behavioral changes (though this applies to all patients, not pregnancy-specific) 2

Bilastine: No Pregnancy Data

There is zero evidence regarding bilastine safety in pregnancy. The provided evidence includes no guidelines, drug labels, or research studies addressing bilastine use during pregnancy. The only mention is a 2026 narrative review discussing its use in allergic rhinitis generally 8, with no pregnancy-specific data.

Alternative Antihistamine Approach

If antihistamine therapy is needed during pregnancy:

• First-generation antihistamines should be avoided due to sedative and anticholinergic properties 6
• Use established second-generation antihistamines with pregnancy safety data (cetirizine, loratadine) rather than bilastine
• The 2016 rhinosinusitis guidelines explicitly recommend avoiding medications without pregnancy safety data 6

Practical Algorithm

1. For asthma control in pregnancy:

   • First-line: Inhaled corticosteroids (budesonide or beclomethasone preferred) 1
   • Second-line: Add montelukast only if conventional therapy fails
   • If already on montelukast pre-pregnancy with good response: continue

2. For allergic rhinitis symptoms:

   • Avoid bilastine entirely (no safety data)
   • Use intranasal corticosteroids as first-line 6
   • If oral antihistamine needed: choose cetirizine or loratadine, not bilastine

3. Combination therapy:

   • Do not use bilastine + montelukast in pregnancy
   • If both leukotriene antagonist and antihistamine are required, use montelukast + established antihistamine (cetirizine/loratadine)

The fundamental principle is that maternal asthma control outweighs theoretical medication risks 1, but this applies only to medications with established safety profiles—bilastine does not qualify.