Comparative Pharmacology
Head-to-head clinical analysis: BENADRYL versus PROMETHAZINE W CODEINE.
Peer-Reviewed Evidence
Head-to-head clinical analysis: BENADRYL versus PROMETHAZINE W CODEINE.
BENADRYL vs PROMETHAZINE W/ CODEINE
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Antihistamine; inverse agonist at histamine H1 receptors, blocking histamine-induced vasodilation, increased capillary permeability, and bronchoconstriction; also anticholinergic and sedative.
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.
25-50 mg orally every 4-6 hours as needed; maximum 300 mg per day. Alternatively, 10-50 mg intramuscularly or intravenously once, maximum 100 mg per dose (IV route preferred).
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 4-8 hours; prolonged in hepatic impairment (up to 20 hours).
Promethazine: 10-19 hours (terminal). Codeine: 2.5-3.5 hours (terminal); prolonged in renal impairment.
Renal (90% as metabolites, <5% unchanged); minimal biliary/fecal.
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