Safety and efficacy of procainamide infusions.

Thirty-four patients who were resistant to conventional doses of lidocaine received procainamide intravenously according to a pharmacokinetically designed two infusion technique. A mean peak serum concentration of 7.1 mg/liter was achieved with an average loading dose of 989 mg administered over 1 hour. A mean steady state serum concentration of procainamide of 6.5 mg/liter was achieved with a mean dose of 64.4 mg/kg body weight for the first 24 hours of treatment. Dose, renal impairment, the degree of congestive heart failure and acetylator status influenced the steady state serum concentration of procainamide. Dangerous ventricular arrhythmias were abolished in 74% of the patients at a steady state level of 6.9 +/- 3.7 mg/liter (mean +/- standard deviation). Nonresponders to procainamide had a mean steady state serum concentration of procainamide of 4.2 +/- 2.1 mg/liter (P less than 0.05). Systolic and diastolic blood pressures decreased moderately (10 and 8%, respectively), and heart rate decreased 11%. The infusion was interrupted in one patient because of hypotension. The duration of electrocardiographic conduction intervals was increased slightly in some patients. It is concluded that procainamide administered by this two infusion method is effective and well tolerated by most patients.