Effects of edrophonium bromide on neuromuscular transmission in a healthy human subject.

Regional intravenous injections of different amounts (1-3 mg) of edrophonium were given to the hand of a healthy subject. The earliest change was a small negative deflection occurring at the end of the muscle response evoked by nerve stimulation, due to repetitive activity. It did not occur after a second stimulus at 30 ms or immediately after 10 s maximum voluntary contraction. Repetitive stimulation at 0.5 Hz reduced the repetitive activity. With a higher dose of edrophonium the response to a second shock (M2) at 30 ms was reduced in amplitude, but M2 at 80 ms was unaffected. An even larger dose caused depression of M2 at 80 ms also and a decremental response to 50 Hz stimulation. The amplitude of the response to a single shock was unchanged throughout.