Disposition and antiarrhythmic effect of lorcainide

The disposition and the antiarrhythmic effect of lorcainide (R 15,889) were investigated in 11 patients with ventricular premature beats (VPB) after a single intravenous dose of 100 mg or 2 mg/kg and after multiple intravenous and oral dosing. Pharmacokinetic parameters were computed according to the two-compartment open model. The half-life of the initial phase, t 1/2 (alpha), was calculated as 0.3 +/- 0.1 hr (mean +/- SD) and the terminal half-life, t 1/2 (beta), varied independently of the dose and route of administration between 5.8 and 12.5 hr (7.8 +/- 2.5 hr). After the single intravenous dose total plasma clearance (Cl) ranged from 570 to 1670 ml/min (988 +/- 425 ml/min) while after multiple dosing Cl decreased to 666 +/- 27 ml/min. Comparison of the area under the curves during steady state (ss) indicated a complete bioavailability of multiple oral doses. After the single intravenous dose, VPB were diminished or reduced for about 4 hr if the plasma concentrations exceeded 120 to 150 ng/ml. During ss-therapy plasma levels fluctuated between 200 and 550 ng/ml with an effective prevention of arrhythmias. Thus, the new drug demonstrates a therapeutic range of approximately 150 to 400 ng/ml and oral therapy seems to be effective with 100 mg t. i. d.