Serum Drug Concentrations in Patients with Ischemic Heart Disease After Administration of a Sustained Release Procainamide Preparation

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Abstract
Despite widespread marketing of a sustained release preparation of pro cainamide hydrochloride (PROCAN-SR, Parke-Davis), published literature demonstrating its efficacy in maintaining uniform serum drug levels over a 6-hour dosing interval is derived from only normal healthy volunteers. Thirty-three patients with ischemic heart disease, ages 30-88 years, were administered 1-4g/24 hours (mean dose 34 mg/kg/day) of PROCAN-SR in 4 equally divided doses on a Q6H schedule. After achievement of steady-state equilibrium drug concentration, procainamide and N-acetylprocainamide levels were determined by high-performance liquid chromatography on sera obtained from blood samples drawn 2, 3.5 and 5 hours after an oral dose. Mean maximal procainamide and N-acetylprocainamide serum concentra tions were 4.6± 1.8 ug/ml and 4.2±2.1 ug/ml respectively. Mean minimal concentrations were 3.5± 1.7 ug/ml and 3.6±2.0 ug/ml respectively. The mean change in drug concentration was small (1.1 ug/ml procainamide and 0.6 ug/ml N-acetylprocainamide) with procainamide and N-acetylprocainamide con centrations varying only by 27 and 15 percent respectively. These data demonstrate in a population of patients with ischemic heart disease, that Q6H dosing with a sustained release procainamide hydrochloride preparation (PROCAN-SR, Parke-Davis) is associated with only a small ac ceptable variation between maximal and minimal serum procainamide and N-acetylprocainamide concentrations. This preparation should, therefore, offer greater patient convenience and compliance without sacrificing antiar rhythmic efficacy.