Quinidine gluconate 324mg; ext-rel tabs. Take with fluid and in an upright position. Individualize. Prevention of premature atrial, nodal and ventricular contractions: 324–648mg every 8–12 hrs.

Quinidine sulfate 300mg; ext-rel tabs. Complete AV or bundle branch block or other severe intraventricular conduction defects. Myasthenia gravis. Arrhythmias due to digitalis intoxication.

3,8 As dextromethorphan is a substrate for CYP2D6 and quinidine is an inhibitor of CYP2D6 and p-glycoprotein, there is the potential for drug interactions. 44 Dose reductions of desipramine ...