Benadryl (Diphenhydramine) Syrup in Pregnancy
Diphenhydramine is safe to use during pregnancy, including the first trimester, with large observational studies confirming no increased risk of congenital malformations. 1, 2, 3
Safety Profile
First-generation antihistamines, including diphenhydramine, have been extensively studied and are considered safe throughout pregnancy. 1, 4, 3
- Large birth registries, case-control studies, and cohort studies confirm the safety of first-generation antihistamines during the first trimester, with no significant increase in congenital malformations. 1
- A comprehensive analysis of 364 associations between 14 antihistamines and 26 isolated major birth defects found results generally consistent with no association, though eight associations involved diphenhydramine, all were weak to moderate in magnitude. 2
- The most critical period for concern about congenital malformations is the first trimester during organogenesis, yet diphenhydramine has demonstrated safety during this period. 1
Approved Indications in Pregnancy
Diphenhydramine is FDA-approved and recommended by ACOG as a first-line pharmacologic treatment for nausea and vomiting in pregnancy when non-pharmacologic measures fail. 1
- First-line non-pharmacologic approaches should be attempted first, including dietary modifications, avoidance of triggers, ginger, and vitamin B6. 1
- If non-pharmacologic approaches fail, first-line pharmacologic options include doxylamine, promethazine, and dimenhydrinate (which contains diphenhydramine). 1
- Diphenhydramine is also considered second-line therapy in anaphylaxis management (25-50 mg parenterally), though it should never be used alone without epinephrine in anaphylactic reactions. 5
Dosing Regimen
Standard adult dosing is 10-20 mL (25-50 mg) every 4-6 hours, not exceeding 6 doses in 24 hours. 6
- Adults and children over 12 years: 10 mL (25 mg) to 20 mL (50 mg) per dose. 6
- Children 6 to under 12 years: 10 mL (25 mg) per dose. 6
- Children under 6 years: Do not use without physician direction. 6
Important Precautions
Before using diphenhydramine, screen for contraindications including chronic bronchitis, glaucoma, and enlarged prostate with urinary retention. 6
- Marked drowsiness may occur; patients should avoid alcohol, sedatives, and tranquilizers, which increase drowsiness. 6
- Caution is advised when driving or operating machinery due to sedation effects. 6
- Excitability may occur, especially in children. 6
- The FDA label states "if pregnant or breast-feeding, ask a healthcare professional before use," but this is standard precautionary language; the evidence supports safety. 6
Breastfeeding Considerations
All antihistamines, including diphenhydramine, are considered safe during breastfeeding, as minimal amounts are excreted in breast milk. 3
Common Pitfall to Avoid
Do not withhold diphenhydramine from pregnant patients based on unfounded teratogenic concerns. The extensive safety data spanning decades supports its use when clinically indicated. 1, 2, 3 However, always attempt non-pharmacologic measures first for conditions like nausea and vomiting. 1