An evaluation of procaine in the treatment of malignant hyperpyrexia.

Procaine has been advocated in the treatment of malignant hyperpyrexia, whereas lignocaine has been shown to worsen the condition. Using muscle from patients susceptible to malignant hyperpyrexia in vitro, it has been demonstrated that muscle contracture can occur with procaine on its own, and in one patient the halothane-induced contracture was potentiated by procaine. In other patients the concentration of procaine required to abolish the halothane-induced contracture was markedly above the clinical dose range. In a study of lignociane and procaine on a caffeinated rat muscle (a suggested model for malignant hyperpyrexia) no significant difference was found in the ability of these local anaesthetics to alter resting tension of halothane-treated muscle; with both drugs the resting tension rose in a dose-related manner. The use of procaine as the drug of first choice in patients with malignant hyperpyrexia is challenged.