title: Verapamil disposition kinetics in chronic atrial fibrillation.
abstract: Verapamil disposition was studied in 12 patients with chronic and fibrillation. After an intravenous bolus of 15 mg plasma concentration was determined and the data fit in a three-compartment model. Model independent parameters were calculated and values for half-life (t 1/2), clearance, and steady-state distribution volume were 6.3 +/- 4 hr, 13.3 +/- 7.7 ml/min/kg, and 4.3 +/- 1.9 l/kg. The model was used to design a multistep infusion scheme, which was employed successfully to achieve predetermined plasma concentrations. Following single oral doses of 120 mg, plasma levels of verapamil and norverapamil were determined. The elimination t 1/2 for verapamil and norverapamil were 8.3 +/- 6.1 and 10.5 +/- 5.6 hr, respectively. The bioavailability of oral verapamil was 35 +/- 16%. During long-term oral therapy the mean verapamil plasma concentration was twice the value predicted from the single-dose studies. This suggests that verapamil may have reduced clearance during long-term oral use.
mesh_terms: D000284:Administration, Oral; D000368:Aged; D001281:Atrial Fibrillation / Q000378:metabolism*; D002908:Chronic Disease; D005260:Female; D006801:Humans; D007263:Infusions, Parenteral; D007275:Injections, Intravenous; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D014700:Verapamil / Q000008:administration & dosage / Q000378:metabolism*
chemical_list: D014700:Verapamil