Trimetaphan Suxamethonium

Trimetaphan can double the duration of suxamethonium block (338-340). The mechanism is not clear, but may be a competitive effect at the neuromuscular junction. Blockade of end-plate ionic channels has also been suggested (341). 

Trimetaphan can increase the effects of suxamethonium (succi-nylcholine), which may result in prolonged apnoea. This may possibly occur with other neuromuscular blocking drugs, such as alcuronium. 

Not fully understood. Trimetaphan can inhibit plasma cholinesterase to some extent, which would reduce the metabolism of the suxamethonium and thereby prolong its activity. Studies in and case reports also indicate that trimetaphan has direct neuromuscular blocking activity. Its effects are at least additive with the neuromuscular blocking effects of the aminoglycosides. ... 

Information is limited but the interaction appears to be established. If trimetaphan and suxamethonium are used concurrently, be alert for enhanced and prolonged neuromuscular blockade. This has also been seen with alcuronium, and trimetaphan may interact with other eompetitive... 

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