ACUTE EFFECTS OF INTRAVENOUS-INJECTION OF BETA-ADRENOCEPTOR-ANTAGONISTS AND CALCIUM-CHANNEL-ANTAGONISTS AND AGONISTS IN MYASTHENIA-GRAVIS

The effect of intravenous injection of propranolol, verapamil, terbuta line, calcium, and edrophonium on neuromuscular transmission has been studied with repetitive nerve stimulation and clinical tests in 10 pat ients with myasthenia gravis (MG). The drugs were given intravenously in doses commonly used in clinical practice. Only minor clinical effec ts were noted except for edrophonium. The mean decrement of the deltoi d muscle was not significantly changed after injection of propranolol (before 31%, 15 min after injection 27%) and verapamil (before 29%, 15 min after injection 26%). Terbutaline applied after propranolol and c alcium applied after verapamil improved the decrement substantially. E drophonium applied after propranolol or verapamil also greatly improve d the decrement. We conclude that there is no rapid deterioration of n euromuscular transmission in patients with moderately severe MG after injections with therapeutic doses of propranolol and verapamil. Howeve r, we do not know if the most severely disabled MG patient could have reacted otherwise. We consider that, in cardiovascular emergencies, pr opranolol and verapamil may be used even in severe MG but with resusci tation equipment as well as specific antidotes available. (C) 1996 Joh n Wiley & Sons, Inc.