Prolonged half-life of verapamil in a case of overdose: implications for therapy.

After an overdose of verapamil (2.4 g) in a 59-year-old man the apparent half-life of verapamil was prolonged (15 h). The most likely mechanism is rate-limiting absorption, although changes in clearance and volume of distribution may contribute. As the elimination half-life of verapamil is increased in overdose, therapy may have to be continued for longer than expected. Moreover since the half-life of absorption of verapamil in overdose may be prolonged, activated charcoal should be given in repeated doses, even if an ordinary-release formulation has been taken.