Comparative Pharmacology
Head-to-head clinical analysis: DEXTROMETHORPHAN HYDROBROMIDE AND QUINIDINE SULFATE versus QUINALAN.
Peer-Reviewed Evidence
Head-to-head clinical analysis: DEXTROMETHORPHAN HYDROBROMIDE AND QUINIDINE SULFATE versus QUINALAN.
DEXTROMETHORPHAN HYDROBROMIDE AND QUINIDINE SULFATE vs QUINALAN
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.
Quinidine (the active ingredient in Quinalan) is a class Ia antiarrhythmic agent that binds to and blocks voltage-gated sodium channels in cardiac myocytes, prolonging the action potential duration and effective refractory period. It also has vagolytic effects and blocks potassium channels.
One capsule (dextromethorphan 20 mg/quinidine 10 mg) orally once daily, with a maximum dose of two capsules per day.
10 mg orally once daily, may increase to 20 mg after 2 weeks if needed.
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 half-life: 12 hours (range 10-14) in normal renal function; prolonged to 24-30 hours in severe renal impairment (CrCl <30 mL/min).
Renal: quinidine 15-25% unchanged, dextromethorphan <1% unchanged; biliary/fecal: quinidine metabolites ~5%, dextromethorphan metabolites ~60-80% as dextrorphan conjugates
Renal: 60% unchanged; Biliary/fecal: 30% as metabolites; 10% other.
Category A/B
Category C
Antiarrhythmic (Class Ia)
Antiarrhythmic (Class Ia)