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

Famotidine Safety During Pregnancy

Famotidine is safe to use during pregnancy as available data do not show an increased risk of birth defects, miscarriage, or adverse maternal or fetal outcomes. 1

Evidence on Famotidine in Pregnancy

The FDA drug label for famotidine provides the most authoritative guidance on its use during pregnancy:

• Famotidine is not associated with major birth defects, miscarriage, or adverse maternal/fetal outcomes based on available data 1
• Animal reproduction studies showed no adverse developmental effects with oral famotidine administration at doses significantly higher than therapeutic human doses 1
• The drug is classified as FDA Pregnancy Category B, indicating animal studies have not demonstrated fetal risk and there are no adequate controlled studies in pregnant women 2

Recent observational research supports these findings:

• A 2024 Japanese cohort study examining 330 women who took famotidine during the first trimester found no significant increase in congenital malformations compared to controls (3.9% vs 2.8%) 3
• While this study noted a higher rate of preterm delivery in the famotidine group (8.1% vs 3.8%), multivariate analysis eliminated famotidine as a causative factor 3

Pharmacokinetics During Pregnancy

• PBPK modeling suggests famotidine exposure decreases by approximately 20-24% during mid and late pregnancy 4
• Despite this decreased exposure, the pharmacodynamic effect on intragastric pH appears to remain adequate 4

Breastfeeding Considerations

• Limited data show famotidine is present in human breast milk 1
• No adverse effects have been reported in breastfed infants 1
• The developmental benefits of breastfeeding generally outweigh potential risks 1

Clinical Recommendations

1. Famotidine can be used safely during all trimesters of pregnancy when clinically indicated
2. No dosage adjustments are specifically recommended for pregnancy, though pharmacokinetic changes occur
3. Famotidine is compatible with breastfeeding

Important Considerations

• All medications during pregnancy carry some level of theoretical risk
• The background risk of major birth defects in the general U.S. population is 2-4%, and miscarriage is 15-20% 1
• When possible, non-pharmacological approaches to managing acid-related disorders should be considered first (dietary modifications, elevation of head of bed)
• Document the clinical necessity of famotidine treatment in the medical record

Famotidine's safety profile makes it a preferred H2-receptor antagonist for use during pregnancy when indicated for acid-related disorders.