Comparative Pharmacology
Head-to-head clinical analysis: PBZ SR versus PROMETHAZINE W DEXTROMETHORPHAN.
Peer-Reviewed Evidence
Head-to-head clinical analysis: PBZ SR versus PROMETHAZINE W DEXTROMETHORPHAN.
PBZ-SR vs PROMETHAZINE W/ DEXTROMETHORPHAN
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Antihistamine; H1-receptor antagonist that competes with histamine for binding at H1 receptor sites, thereby preventing histamine-mediated allergic responses.
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.
100-200 mg orally every 12 hours; maximum 400 mg/day.
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.
None Documented
None Documented
Terminal elimination half-life is approximately 4-6 hours in adults with normal renal function; clinically relevant dosing every 4-6 hours is recommended.
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.
Primarily renal excretion (80-90% as unchanged drug) via glomerular filtration and tubular secretion. Biliary/fecal excretion accounts for approximately 5-10%.
Renal: promethazine ~6% unchanged, dextromethorphan ~0.5% unchanged; metabolites primarily renal. Biliary/fecal: minor routes for both.
Category C
Category A/B
Antihistamine
Antihistamine / Antiemetic