Comparative Pharmacology
Head-to-head clinical analysis: PROMETHAZINE W DEXTROMETHORPHAN versus VISTARIL.
Peer-Reviewed Evidence
Head-to-head clinical analysis: PROMETHAZINE W DEXTROMETHORPHAN versus VISTARIL.
PROMETHAZINE W/ DEXTROMETHORPHAN vs VISTARIL
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.
Hydroxyzine is a piperazine derivative antihistamine that acts as a competitive antagonist of histamine H1 receptors, thereby suppressing histamine activity in the subcortical area of the central nervous system. It also has anxiolytic, sedative, antiemetic, and antispasmodic effects.
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.
Oral: 50-100 mg 4 times daily; IM: 25-100 mg every 4-6 hours as needed.
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: 20-25 hours in adults; prolonged in hepatic impairment or elderly; steady-state achieved in ~4-5 days.
Renal: promethazine ~6% unchanged, dextromethorphan ~0.5% unchanged; metabolites primarily renal. Biliary/fecal: minor routes for both.
Primarily hepatic metabolism; <1% excreted unchanged in urine; biliary/fecal elimination of metabolites accounts for approximately 50-60% of total clearance.
Category A/B
Category C
Antihistamine / Antiemetic
Antihistamine