Chlorpheniramine Dosing in Pregnancy
Chlorpheniramine can be used during pregnancy at standard doses of 4-12 mg when necessary, with preference for the lowest effective dose for the shortest duration possible, especially during the first trimester. 1
Safety Profile and Recommendations
- Chlorpheniramine is often chosen by clinicians when antihistamine therapy is necessary during pregnancy because of its long safety record 1
- First-generation antihistamines, including chlorpheniramine, have excellent safety records and do not show a significant increase in congenital malformations when used during the first trimester 1
- It is best to avoid all antihistamines in pregnancy when possible, especially during the first trimester, although none has been shown to be teratogenic in humans 1, 2
- When treatment is necessary, use the lowest effective dose for the shortest possible time to minimize exposure 2, 3
Dosing Guidelines
- Standard dosing for chlorpheniramine in adults, including pregnant women, is 4-12 mg 1
- For nighttime use, chlorpheniramine 4-12 mg may be added to a non-sedating antihistamine used during the day 1, 2
- Avoid chlorpheniramine in patients with severe liver disease due to inappropriate sedating effects 1, 2
Important Considerations
- Sedation is a common side effect of chlorpheniramine that may affect performance and concentration 1, 2
- Performance impairment can occur without subjective awareness of drowsiness 2
- Chlorpheniramine has a long half-life (19-43 hours), which can lead to significant accumulation with frequent daily dosing 4
- The pharmacokinetics of chlorpheniramine may be altered during pregnancy due to physiological changes, potentially requiring dose adjustments 5, 6
Alternative Options
- Second-generation antihistamines (loratadine, cetirizine) are FDA Pregnancy Category B drugs and may be considered as alternatives with less sedation 1, 2
- These newer antihistamines have been confirmed safe through large birth registries, case-control studies, and cohort studies 1