title: Electrophysiologic effects of procainamide in subtherapeutic to therapeutic doses on human atrioventricular conduction system.
abstract: The effects of single intravenous infusions of 50 to 400 mg of procainamide on the functional properties of the atrioventricular (A-V) conduction system were studied in 36 patients and correlated with plasma concentrations. A 50 mg dose of procainamide resulted in a plasma concentration of less than 1.0 mug/ml and produced no electrophysiologic changes. Doses of 100, 200, 300 and 400 mg resulted in progresively increasing plasma concentrations (1.2, 1.8, 3.5 and 4.2 mug/ml, respectively). The effects of procainamide on the sinus rate were variable and not dose-related. The effects of doses of up to 300 mg on A-V nodal conduction were variable and not dose-related. Only in a dose of 400 mg did procainamide prolong A-V nodal conduction in six of seven patients. Whereas 100 mg had no effect on His-Purkinje system conduction, doses of 200, 300 and 400 mg prolonged His-Purkinje system conduction time by 6, 8 and 9 msec, respectively. Dose-related increases in atrial refractoriness started with a dose of 200 mg and became statistically significant with doses of 300 and 400 mg. The effects of procainamide on A-V nodal functional refractoriness were variable and not dose-related, but in doses of 100 to 400 mg, procainamide produced significant and progressively dose-related increases in His-Purkinje system refractoriness. Suppression of some types of ventricular arrhythmia by small doses of this drug may be explained by changes in refractoriness of the His-Purkinje system produced by doses of procainamide as small as 100 mg.
mesh_terms: D001283:Atrioventricular Node / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002986:Clinical Trials as Topic; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D006329:Heart Conduction System / Q000187:drug effects*; D006331:Heart Diseases / Q000503:physiopathology; D006801:Humans; D007263:Infusions, Parenteral; D008875:Middle Aged; D011342:Procainamide / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*
chemical_list: D011342:Procainamide