Is famotidine (Histamine-2 (H2) blocker) safe to use during pregnancy?

Famotidine Use During Pregnancy

Famotidine is safe to use during pregnancy as there is no evidence of increased risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes. 1

Safety Profile

Famotidine is classified as an FDA Pregnancy Category B medication, which means:

• Animal reproduction studies have shown no adverse developmental effects with oral administration of famotidine at doses up to approximately 243 times the recommended human dose 1
• Available data with H2-receptor antagonists, including famotidine, in pregnant women are insufficient to establish a drug-associated risk of major birth defects or miscarriage 1
• A recent observational cohort study found no significant difference in congenital malformation rates between pregnant women who took famotidine during the first trimester (3.9%) compared to controls (2.8%) 2

Pharmacokinetic Considerations

• Famotidine exposure is decreased by approximately 24% in mid-pregnancy and 20% in late pregnancy compared to non-pregnant women 3
• Despite these changes, the pharmacodynamic effect on intragastric pH appears to be maintained during pregnancy 3

Recommendations for Use

1. First Trimester:

   • While famotidine has not shown evidence of teratogenicity, if possible, consider avoiding all antihistamines during the first trimester as a general precaution 4
   • If treatment is necessary, famotidine can be used as there is no significant increased risk of congenital malformations 2

2. Second and Third Trimesters:

   • Famotidine can be used when clinically indicated 4
   • No evidence of increased adverse pregnancy outcomes has been observed 2

Potential Concerns

• A higher rate of preterm delivery was initially detected in famotidine users compared to controls (8.1% vs 3.8%), but multivariate analysis eliminated famotidine use as a causative factor, suggesting this was due to other confounding factors such as underlying medical conditions 2

Breastfeeding Considerations

• Limited data are available on the presence of famotidine in human breast milk 1
• No adverse effects on breastfed infants have been reported 1
• The developmental and health benefits of breastfeeding should be considered alongside the mother's clinical need for famotidine 1

Alternative Medications

When treating gastrointestinal conditions during pregnancy:

• For allergic rhinitis during pregnancy, intranasal corticosteroids may be preferred as first-line therapy over oral antihistamines 4
• Avoid oral decongestants if possible during the first trimester due to reports of association with congenital malformations 5

In summary, famotidine can be safely used throughout pregnancy when clinically indicated, with no evidence of increased risk of congenital malformations or other adverse pregnancy outcomes.