Comparative Pharmacology
Head-to-head clinical analysis: PROMETHAZINE W DEXTROMETHORPHAN versus TIGAN.
Peer-Reviewed Evidence
Head-to-head clinical analysis: PROMETHAZINE W DEXTROMETHORPHAN versus TIGAN.
PROMETHAZINE W/ DEXTROMETHORPHAN vs TIGAN
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.
TIGAN (trimethobenzamide) acts on the chemoreceptor trigger zone (CTZ) to inhibit emetic stimuli, primarily through antagonism of dopamine D2 receptors, though its exact mechanism is not fully elucidated.
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.
Adults: 200 mg IM or 100 mg PO or 200 mg PR every 6–8 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.
12-15 hours; may be prolonged in hepatic impairment.
Renal: promethazine ~6% unchanged, dextromethorphan ~0.5% unchanged; metabolites primarily renal. Biliary/fecal: minor routes for both.
Renal (30-50% as unchanged drug and metabolites), biliary/fecal (minor).
Category A/B
Category C
Antihistamine / Antiemetic
Antiemetic