title: The effect of oral verapamil therapy on antipyrine clearance.
abstract: The influence of chronic verapamil treatment on antipyrine elimination was studied in eight angina patients. Antipyrine half-life (mean +/- s.d.) was 13.1 +/- 1.15 h at the start of therapy and 16.6 +/- 3.05 h (P less than 0.05) during chronic oral administration of verapamil (80-120 mg four or three times daily for 4 to 7 months). There was a significant decrease in antipyrine clearance (mean +/- s.d, 43.2 +/- 16.8 ml min-1 vs 28.7 +/- 16.6 ml min-1, P less than 0.01) while the change of distribution volume was insignificant. Verapamil elimination was also found to be impaired after chronic dosing as compared to single administration. Half-lives measured from the concentration vs time and urinary excretion rate vs time curves were both prolonged and oral clearance was decreased. Our results suggest that the inhibition of drug-metabolizing enzymes accounts for the impairment of verapamil elimination on chronic administration.
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000787:Angina Pectoris / Q000188:drug therapy; D000983:Antipyrine / Q000378:metabolism*; D006207:Half-Life; D006801:Humans; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D014700:Verapamil / Q000008:administration & dosage / Q000378:metabolism* / Q000627:therapeutic use
chemical_list: D014700:Verapamil; D000983:Antipyrine