Comparative Pharmacology
Head-to-head clinical analysis: DIPHENHYDRAMINE HYDROCHLORIDE PRESERVATIVE FREE versus PROMETHAZINE DM.
Peer-Reviewed Evidence
Head-to-head clinical analysis: DIPHENHYDRAMINE HYDROCHLORIDE PRESERVATIVE FREE versus PROMETHAZINE DM.
DIPHENHYDRAMINE HYDROCHLORIDE PRESERVATIVE FREE vs PROMETHAZINE DM
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Competitive antagonist of histamine H1 receptors; centrally acting anticholinergic agent that inhibits acetylcholine muscarinic receptors.
Promethazine is a phenothiazine derivative that acts as a histamine H1 receptor antagonist, antiemetic via blockade of dopamine D2 receptors in the chemoreceptor trigger zone, and sedative via central anticholinergic effects. Dextromethorphan is an NMDA receptor antagonist and sigma-1 receptor agonist, suppressing cough by central action on the cough center.
25 to 50 mg intravenously or intramuscularly every 4 to 6 hours as needed; maximum 400 mg per day.
2 teaspoonfuls (10 mL) orally every 4-6 hours, not to exceed 8 teaspoonfuls (40 mL) per 24 hours.
None Documented
None Documented
Terminal elimination half-life: 4-10 hours (mean ~8 hours); prolonged in hepatic impairment or elderly (up to 20 hours).
16-19 hours (terminal); note: effect may last longer due to active metabolites and tissue binding
Primarily renal as inactive metabolites; ~60% of a dose appears in urine as metabolites, with <5% unchanged. Minor biliary/fecal elimination (<10%).
Renal (70-80% as metabolites, <1% unchanged); biliary/fecal (20-30%)
Category A/B
Category A/B
Antihistamine
Antihistamine / Antiemetic