Noneffectiveness of verapamil in preventing halothane-induced malignant hyperthermia in susceptible swine.

Pietrain pigs susceptible to malignant hyperthermia (MH; porcine stress syndrome) were treated with the slow-channel calcium blocker verapamil and then subjected to halothane testing. There was no significant delay in the onset of MH among pigs (3 groups) given different doses of verapamil (1, 5, and 10 mg/kg) and saline control Pietrain pigs. The mortality due to MH (83.3%) was significantly higher among the pigs given the largest dose (10 mg/kg) than in the other groups. Verapamil was not effective in preventing or delaying a MH reaction. This antiarrhythmic drug should be used cautiously during a MH reaction in susceptible individuals.