Pharmacokinetics of a sustained release procainamide preparation.

In summary, procainamide is a useful agent for suppressing premature depolarization frequency. Its short half-life of elimination requires a dosing frequency of every 3 hours with regular dosage forms or every 6-8 hours with a sustained action dosage. Because of the extreme unpredictability of plasma concentration, the dosage must be titrated in each patient with electrocardiographic monitoring serving as the most useful method of evaluating efficacy. Maximum and minimum plasma concentrations are helpful in monitoring the achievement of therapeutic plasma levels and adjusting the frequency of dosing, especially in the presence of impaired renal function or low cardiac output. Adverse effects of procainamide include anorexia, nausea, vomiting, fatigue, insomnia, visual hallucinations, and disorientation; these are minor and cease with discontinuation of the drug. Agranulocytosis has rarely been reported. Long-term treatment has resulted in the occurrence of a lupus-like syndrome that is reversible when the drug is stopped. Procainamide is excreted in breast milk and infants of mothers receiving procainamide should not be nursed.