1. Drugs. 1982 Sep;24(3):229-39. Quinidine and digoxin. An important interaction. Bigger JT Jr, Leahey EB Jr. An increase in serum digoxin concentration occurs in 90% of patients given quinidine. Quinidine gluconate, quinidine polygalacturonate, and quinidine sulfate darken on exposure to light and should be stored in well closed, light-resistant containers. Solutions of quinidine salts slowly acquire a brownish tint on exposure to light. Quinidine is a pharmaceutical agent that acts as a class I antiarrhythmic agent (Ia) in the heart. It is a stereoisomer of quinine , originally derived from the bark of the cinchona tree. The drug causes increased action potential duration, as well as a prolonged QT interval. Find patient medical information for Quinidine Sulfate Oral on WebMD including its uses, side effects and safety, interactions, pictures, warnings and user ratings. Digoxin and quinidine sulfate are used. The decision to treat a horse with atrial fibrillation at low heart rates depends on the requirement for the horse to perform work, because horses with this arrhythmia can be retired and will live for several years. They may be used successfully as brood mares. Anticoagulation therapy is not administered to horses in atrial fibrillation because of the. Quinidine Sulfate (quinidine sulfate) Tablet, Film Coated, Extended Release. DESCRIPTION. Quinidine is an antimalarial schizonticide and an antiarrhythmic agent with Class la activity; it is the d-isomer of quinine, and its molecular weight is 324.43. An open randomized crossover trial to investigate quinidine-digoxin interactions under steady-state conditions with special attention to quinidine pharmacokinetics was performed in 6 healthy male volunteers. Coadministration of quinidine sulphate induces a prolongation of digoxin elimination half Each tablet, for oral administration, contains 200 mg of quinidine sulfate (equivalent to 166 mg of quinidine base) 300 mg of quinidine sulfate (equivalent to 249 mg of quinidine base). In addition, each tablet contains the following inactive ingredients: confectioner’s sugar, corn starch, microcrystalline cellulose, pregelatinized starch and zinc stearate. The results may be explained by the displacement of digoxin from binding sites in tissue by quinidine, causing a rise in the plasma concentration of digoxin. The reduction in renal clearance of. Although the effect of food upon Quinidex (quinidine) absorption has not been studied, peak serum quinidine levels obtained from immediate-release quinidine sulfate are known to be delayed by nearly an hour (without change in total absorption) when these products are taken with food.