Comparative Pharmacology
Head-to-head clinical analysis: DEXTROMETHORPHAN HYDROBROMIDE AND QUINIDINE SULFATE versus NORPACE CR.
Peer-Reviewed Evidence
Head-to-head clinical analysis: DEXTROMETHORPHAN HYDROBROMIDE AND QUINIDINE SULFATE versus NORPACE CR.
DEXTROMETHORPHAN HYDROBROMIDE AND QUINIDINE SULFATE vs NORPACE CR
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Dextromethorphan is an uncompetitive NMDA receptor antagonist and sigma-1 receptor agonist; quinidine is a CYP2D6 inhibitor that increases dextromethorphan bioavailability.
Class Ia antiarrhythmic agent; decreases myocardial excitability and conduction velocity, and prolongs refractory period by blocking sodium channels.
One capsule (dextromethorphan 20 mg/quinidine 10 mg) orally once daily, with a maximum dose of two capsules per day.
Disopyramide controlled-release: 200 mg orally every 12 hours; maximum 400 mg/day.
None Documented
None Documented
Dextromethorphan: 2-4 hours (extensive metabolizers); quinidine: 6-8 hours (inhibits CYP2D6, prolonging dextromethorphan half-life in poor metabolizers to >20 hours)
Terminal elimination half-life: 6-12 hours (normal renal function); prolonged to 12-20 hours in renal impairment. In coronary artery disease, half-life may be extended due to reduced clearance.
Renal: quinidine 15-25% unchanged, dextromethorphan <1% unchanged; biliary/fecal: quinidine metabolites ~5%, dextromethorphan metabolites ~60-80% as dextrorphan conjugates
Renal (50-57% unchanged), hepatic metabolism (30-40%), fecal (<10%). Dose adjustment required for CrCl <40 mL/min.
Category A/B
Category C
Antiarrhythmic (Class Ia)
Antiarrhythmic (Class Ia)