IN VITRO STUDY OF INTERACTIONS BETWEEN I.V. ANAESTHETICS AND NEUROMUSCULAR BLOCKING AGENTS

The interactions of four anaesthetic drugs (ketamine, propanidid,Althesin and methohexitone) with two neuromuscular blockingagents (suxamethonium and pancuronium) have been investigated.On the isolated rat phrenic nerve—diaphragm preparation,all the anaesthetic drugs examined potentiated suxamethoniummore than they potentiated pancuronium. The anticholinesteraseagent, ecothiopate, had no significant effect on the potentiationof suxamethonium caused by the anaesthetic drugs. At low concentrationsthe anaesthetic drugs increased the twitch tension elicitedby stimulation of the phrenic nerve, whilst at high concentrationsthis potentiation was followed by blockade of neuromusculartransmission. With the exception of Althesin, all the anaestheticsdecreased the sensitivity of the frog rectus preparation toacetylcholine. The possible sites and mechanisms of these interactionsare discussed.