Lithium and neuromuscular transmission.

The actions of lithium on end-plate depolarization and on indirect and direct twitch response of isolated guinea pig muscle were investigated. At clinical concentrations lithium did not cause depolarization, nor did it affect the depolarizing action of carbachol. Lithium also had no effect on the twitch response to nerve stimulation throughout its therapeutic serum concentration range and it did not alter the ED50 of pancuronium. When animals were chronically pretreated with lithium there appeared to be a slight reduction in dosage requirement for d-tubocurarine. At concentrations well above therapeutic serum levels, end-plate depolarization as well as indirect and direct twitch responses were depressed. It is concluded that, at therapeutic levels, there is minimal interaction of lithium with competitive neuromuscular blocking agents.