The information on the pharmacokinetics of verapamil in overdose is sc
anty. We report two adults who ingested 3.2 g and 4 g of verapamil, re
spectively. Both patients had hypotension and a severe bradycardia. Th
e highest plasma verapamil concentration in these patients was about 2
200 ng/ml and 2700 ng/ml, respectively. The decline in plasma verapami
l and norverapamil concentrations followed first-order kinetics, and t
he half-life of verapamil was 7.8 h and 15.1 h, respectively. The free
fraction of verapamil (non-protein bound) was higher at total concent
rations exceeding 2000 ng/ml (12-15%) than at lower concentrations (2-
6%). There seems to be no marked saturation of the metabolism of verap
amil in acute poisoning. The apparent concentration-dependent changes
in the free fraction may be due to therapeutic measures.