What is the recommended dose of Brompheniramine (antihistamine) for an adult?

Brompheniramine Dosing for Adults

For adults, the recommended dose of brompheniramine is 10 mL (2 teaspoonfuls) or 4 mg every 4 hours, not exceeding 6 doses in 24 hours. 1

Standard Oral Dosing

• Adults and patients ≥12 years: 10 mL (2 teaspoonfuls) every 4 hours, with a maximum of 6 doses per 24-hour period 1
• This translates to approximately 4 mg per dose when using standard formulations 1
• The dosing interval of every 4 hours is based on the drug's pharmacokinetic profile, though the actual half-life is considerably longer at approximately 25 hours 2

Sustained-Release Formulations

• 12 mg sustained-release preparations are available and have been studied in clinical trials 3, 4, 5
• These formulations are typically dosed twice daily (morning and evening) rather than every 4 hours 3
• Sustained-release preparations may provide prolonged antihistaminic activity while potentially reducing the frequency of peak sedative effects 4

Clinical Efficacy Considerations

• Brompheniramine demonstrates significant antihistaminic effects at serum concentrations of 7-10 ng/mL, which correspond to standard dosing regimens 2
• The drug shows prolonged suppression of histamine-induced wheal and flare responses lasting up to 48 hours after a single dose, with significant pruritus suppression for 24 hours 2
• In clinical trials for rhinovirus colds, 12 mg twice daily effectively reduced rhinorrhea, sneezing, and cough compared to placebo 6

Important Safety Considerations

• Sedation is the primary adverse effect, typically lasting 6 hours after immediate-release formulations 3
• Tolerance to drowsiness develops after repeated dosing (by day 2 of treatment) 3
• The drug causes minimal objective impairment of psychomotor performance at therapeutic doses, though subjective drowsiness is common 3, 4
• Sustained-release systems with non-linear drug release may cause more pronounced early sedation compared to linear-release systems 5

Practical Prescribing Algorithm

1. For acute allergic symptoms: Start with 4 mg (10 mL) every 4 hours as needed, maximum 6 doses daily 1
2. For chronic conditions requiring continuous coverage: Consider 12 mg sustained-release formulation twice daily (morning and evening) 3
3. Monitor for sedation particularly during the first 2-6 hours after dosing 3, 4
4. Advise patients that drowsiness typically improves with continued use after 1-2 days 3
5. Avoid activities requiring alertness (driving, operating machinery) during the first few hours after dosing until individual response is known 4, 5