Possible Interaction: Propafenone and Quinidine

“Low-dose quinidine may promote the efficacy of propafenone by inhibiting its degradation through the cytochrome P450 pathway (CYP2D6).”

“Of the 10 refractory patients, 7 were further controlled with a standard dose of propafenone plus quinidine (600 mg/day).”

“In this study we tested the hypothesis that quinidine would enhance β‐blockade in extensive metabolizers receiving propafenone.”

“Subtherapeutic doses of quinidine inhibit P4502D6 and increase plasma propafenone in extensive metabolizer subjects, in whom the active enzyme is present.”

“Other antiarrhythmics such as beta-blockers, calcium channel blockers, and amiodarone have been used effectively also; however, some antiarrhythmics such as lidocaine, mexiletine, propafenone , and quinidine may exacerbate neuromuscular symptoms and should be used cautiously.”

“Throughout the study (follow‐up, 199 ± 155 days), quinidine successfully inhibited CYP2D6: propafenone concentrations were 3 times higher in patients receiving quinidine (1033 ± 611 ng/mL vs 328 ± 229 ng/mL; P < .001).”

“In patients with the extensive metabolizer phenotype, quinidine increased mean steady-state plasma propafenone concentrations more than two fold, from 408 +/- 351 (mean +/- s.d.)”

“Additive pharmacologic effect can occur when lidocaine, procainamide, and quinidine are combined with propafenone.”

“In 30 patients, the addition of propafenone resulted in a significant reduction of premature ventricular contraction (PVC) frequency compared to drug-free baseline (406 PVC/hr vs 33, p less than 0.001) and to procainamide or quinidine monotherapy (211 PVC/hr vs 27, p less than 0.01).”

“A novel analytical procedure, first beat phasic block determination, provided the opportunity to estimate … single action potential.1.TotalVmax blockade increased in response to the addition of quinidine (1×10−5 mol/l), lidocaine (3×10−5 or … prajmalium (2.5×10−5 mol/l) to a propafenone-containing (….”