Muscle weakness during tricaine anesthesia.

An isolated preparation of tadpole tail muscle was used to assess the peripheral effects of tricaine (3-aminobenzoic acid ethyl ester) at anesthetic concentrations and under physiological conditions. The drug effect on the electrically-evoked twitch was tested using short-pulse durations that elicited synaptically mediated effects or longer-duration pulses that stimulated the muscle directly. Tricaine reduced both types of response anesthetic and even subanesthetic concentrations. At steady state concentrations that produced surgical anesthesia in vivo, tricaine reduced the directly evoked response by about half. It is concluded that tricaine anesthesia has a pronounced peripheral effect on neuromuscular function and that direct effect(s) on muscle are a major component.