Comparative Pharmacology
Head-to-head clinical analysis: BENADRYL versus PROMETHAZINE HYDROCHLORIDE CODEINE PHOSPHATE.
Peer-Reviewed Evidence
Head-to-head clinical analysis: BENADRYL versus PROMETHAZINE HYDROCHLORIDE CODEINE PHOSPHATE.
BENADRYL vs PROMETHAZINE HYDROCHLORIDE; CODEINE PHOSPHATE
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.
Promethazine is a phenothiazine derivative that acts as a histamine H1 receptor antagonist, antiemetic, and sedative via blockade of central and peripheral H1 receptors and antagonism of dopamine D2 receptors. Codeine is an opioid agonist that binds to mu-opioid receptors in the CNS, producing analgesia and cough suppression; it also has antitussive effects via central action.
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).
Promethazine hydrochloride 6.25-25 mg / codeine phosphate 10-20 mg (based on codeine component) orally every 4-6 hours as needed. Maximum codeine dose: 60 mg per dose, 120 mg per day.
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: 2.4-4 hours (terminal), prolonged in hepatic impairment. Clinical context: Dosing interval typically 4-6 hours for codeine; promethazine accumulates with repeated dosing.
Renal (90% as metabolites, <5% unchanged); minimal biliary/fecal.
Promethazine: Renal (70-80% as metabolites, <1% unchanged); Codeine: Renal (70-90% as metabolites, 5-15% unchanged). Biliary/feces: Minor (<10% total).
Category C
Category A/B
Antihistamine
Antihistamine / Antiemetic