Comparative Pharmacology
Head-to-head clinical analysis: BENYLIN versus PROMETHAZINE W CODEINE.
Peer-Reviewed Evidence
Head-to-head clinical analysis: BENYLIN versus PROMETHAZINE W CODEINE.
BENYLIN vs PROMETHAZINE W/ CODEINE
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.
Codeine is a prodrug converted to morphine, a mu-opioid receptor agonist, which inhibits nociceptive transmission; promethazine is a phenothiazine derivative with H1-receptor antagonism, anticholinergic, and antiemetic effects.
Oral: 10-20 mL (25-50 mg diphenhydramine) every 4-6 hours; maximum 100 mg per day.
10 mL (1 mg codeine, 6.25 mg promethazine per 5 mL) orally every 4-6 hours as needed for cough. Maximum: 60 mL per day. Do not exceed 5 days.
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 (terminal). Codeine: 2.5-3.5 hours (terminal); prolonged in renal impairment.
Renal: ~80% as unchanged drug and glucuronide conjugates; fecal/biliary: ~20%.
Promethazine: renal (70% as metabolites, <1% unchanged), fecal (20-30%). Codeine: renal (90%, of which 5-10% unchanged, rest as metabolites), fecal (minor).
Category C
Category A/B
Antihistamine
Antihistamine / Antiemetic