Sensitivity of Myasthenia Gravis Patients to Tubocurarine and Decamethonium

Abstract

Threshold paralytic doses of tubocurarine and decamethonium were detd. in 30 subjects with myasthenia gravis and 22 non-myasthenic subjects. Patients with myasthenia gravis (mean threshold dose 5.42 [mu]g/kg.) were 5.5 times as sensitive to tubocurarine as were non-myasthenic subjects (mean threshold dose 24.77 [mu]g./kg.). About 3-4% of normal subjects are as sensitive to tubocurarine as an avg. patient with myasthenia gravis. About 3-4% of patients with myasfhenia gravis are not abnormally sensitive to threshold doses of tubocurarine. Patients with myasthenia gravis were not more sensitive to decamethonium than were non-myasthenic subjects. With subthreshold doses of decamethonium, patients with myasthenia gravis experienced transient amelioration of the signs and symptoms of the disease. Results are consistent with the concept that the fundamental feature of myasthenia gravis is a blockade of the neuromuscular junction by a substance or process which decreases the muscular response to acetylcholine.