Effect of diazepam on neuromuscular transmission and its interaction with non-depolarizing muscle relaxants

Neuromuscular blocking actions of diazepam and its interaction with some myoneural blocking agents were studied in dogs and in humans undergoing surgery under general anaesthesia. Diazepam alone had no effect on the response of tibialis anterior muscle to indirect stimulation in dogs. Again, diazepam in a bolus dose of 5 mg did not influence a pre-existing partial block by d-tubocurarine, gallamine or pancuronium. But a significant increase in both the degree and duration of block was observed when diazepam and d-tubocurarine were given simultaneously, suggesting an agonist action in diazepam. On the contrary, simultaneous use of diazepam and gallamine caused a significantly less intense block of tibialis muscle twitch tension as compared to gallamine alone, suggesting an antagonistic action. The degree and duration of block by d-tubocurarine were not affected significantly by simultaneous administration of diazepam in human beings. It is, therefore, concluded that diazepam in clinical doses can be safely used with d-tubocurarine in humans.