Kinetics of the Oral Antiarrhythmic Lidocaine Congener, Tocainide

Tocainide, a primary amine analogue of lidocaine, is effective against some experimental and clinical arrhythmias. Its pharmacokinetic behavior was studied in 6 healthy male subjects. Peak blood levels (CB max) and area under the blood concentration-time curve (AUC) were linearly related to dose with slopes of 0.0067 mcg/ml and 6 min mcg/ml per milligram of dose, respectively. Renal clearance of tocainide averaged 59 ml/min when urinary pH was uncontrolled or acidified, while it was reduced to 13 ml/min during intense sodium bicarbonate loading. Blood levels following intravenous infusion were well described by a 2-compartment open model with a volume of the central compartment of 0.92 L/kg. The t 1/2 beta was 11 hr and total body clearance was 166 ml/min. Loo-Riegelman analysis of the absorption rate did not allow unequivocal assignment of an "order" to the absorption process. Bioavailability approached 100%. Administration of drug 5 min after a test meal suppressed CB max 40% but minimally affected AUC. Approximately 50% of the drug was found to be plasma protein bound at clinically effective concentrations.