Comparative Pharmacology
Head-to-head clinical analysis: PROMETHAZINE W DEXTROMETHORPHAN versus TEMARIL.
Peer-Reviewed Evidence
Head-to-head clinical analysis: PROMETHAZINE W DEXTROMETHORPHAN versus TEMARIL.
PROMETHAZINE W/ DEXTROMETHORPHAN vs TEMARIL
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Promethazine is a phenothiazine derivative that acts as a histamine H1 receptor antagonist and antiemetic; dextromethorphan is a non-opioid antitussive that acts as an NMDA receptor antagonist and sigma-1 receptor agonist.
Temaril (trimeprazine tartrate and prednisolone) combines an antipruritic phenothiazine antihistamine with a corticosteroid. Trimeprazine blocks histamine H1 receptors, reducing pruritus and allergic reactions. Prednisolone suppresses inflammation via glucocorticoid receptor activation, inhibiting phospholipase A2 and cytokine production.
5 mL (containing promethazine 6.25 mg and dextromethorphan 15 mg) orally every 4-6 hours as needed, not to exceed 30 mL (promethazine 37.5 mg, dextromethorphan 90 mg) per 24 hours.
2.5 mg orally twice daily or 5 mg orally at bedtime; maximum 10 mg/day.
None Documented
None Documented
Promethazine: 9-16 h; dextromethorphan: 3-5 h (extensive metabolizers), 30-50 h (poor metabolizers). Clinical context: dosing interval typically 4-6 h for dextromethorphan; promethazine accumulates with repeated dosing.
Terminal elimination half-life is 9–12 hours in adults; prolonged in hepatic impairment (up to 20 hours). Given TID dosing, steady state is reached within 2 days.
Renal: promethazine ~6% unchanged, dextromethorphan ~0.5% unchanged; metabolites primarily renal. Biliary/fecal: minor routes for both.
Primarily via kidneys as metabolites; unchanged drug accounts for <1%. Biliary/fecal excretion is minor. Approx. 90% recovered in urine within 24 hours.
Category A/B
Category C
Antihistamine / Antiemetic
Antihistamine