Comparative Pharmacology
Head-to-head clinical analysis: BENYLIN versus PROMETHAZINE HYDROCHLORIDE AND CODEINE PHOSPHATE.
Peer-Reviewed Evidence
Head-to-head clinical analysis: BENYLIN versus PROMETHAZINE HYDROCHLORIDE AND CODEINE PHOSPHATE.
BENYLIN vs PROMETHAZINE HYDROCHLORIDE AND CODEINE PHOSPHATE
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
BENYLIN (diphenhydramine) is a first-generation antihistamine that competitively antagonizes histamine at H1 receptors, thereby alleviating allergic symptoms. It also crosses the blood-brain barrier and acts as a central nervous system depressant via inhibition of histamine and acetylcholine, producing sedative, antiemetic, and antitussive effects.
Promethazine is a phenothiazine derivative that antagonizes histamine H1 receptors, reducing allergic symptoms; it also has anticholinergic, antiemetic, and sedative effects. Codeine is an opioid agonist at mu-opioid receptors, producing analgesia and antitussive effects by central mechanisms.
Oral: 10-20 mL (25-50 mg diphenhydramine) every 4-6 hours; maximum 100 mg per day.
Adults: 5 mL (containing promethazine 6.25 mg and codeine 10 mg) orally every 4-6 hours as needed; maximum 30 mL per day.
None Documented
None Documented
Terminal elimination half-life: 4-6 hours in adults; extended to 10-12 hours in hepatic impairment, increasing risk of accumulation.
Promethazine: 10-19 hours (range 5-30h); Codeine: 2.5-4 hours (rapidly metabolized); Clinical context: sustained antitussive effect from codeine despite short half-life. Half-life of promethazine extends with hepatic impairment.
Renal: ~80% as unchanged drug and glucuronide conjugates; fecal/biliary: ~20%.
Renal: Codeine and metabolites ~90% (free and conjugated), Promethazine and metabolites primarily renal; minor biliary/fecal (<5% for codeine, ~6% for promethazine).
Category C
Category A/B
Antihistamine
Antihistamine / Antiemetic