Physiological disposition of verapamil in man.
14C-D,L-verapamil was administered intravenously (10 mg) and orally (80 mg) to five volunteer patients. Plasma concentrations of verapamil, which were determined by mass fragmentography, declined bi-exponentially with half-lives of the chi-phase ranging from 18 to 35 min and of the beta-phase from 170 to 440 min. The apparent volume of distribution ranged from 270 to 460 litre and plasma clearance from 730 to 1980 ml/min. Following oral administration absorption was almost complete as judged from the area under the curve (AUC) of 14C-activity and cumulative urinary excretion of 14C. After intravenous infusion of verapamil about 80% of the radioactivity administered could be recovered in urine and faeces within 5 d. Despite its almost complete absorption after oral administration verapamil was shown to undergo extensive first pass metabolism as the bioavailability was only 10 to 22%. Rapid biotransformation had occurred as only a small percentage of AUC of 14C was seen to correspond to unchanged verapamil after both intravenous and oral administration.
D000284:Administration, Oral; D000368:Aged; D001682:Biological Availability; D005243:Feces / Q000032:analysis; D006207:Half-Life; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D011485:Protein Binding; D014700:Verapamil / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*
D014700:Verapamil