Suxamethonium Procainamide

The place of the dmg in dentistry [153 4] and in electro-convulsive therapy [ 154] (with a description of a technique to surmount difficulties arising from the concurrent use ot suxamethonium) has been evaluated. A refined radio telemetric technique has enabled a detailed study [155] of the cardiovascular effects of propanidid to be made, resulting in strong evidence for a transient procainamide- or quinidine-like depression of myocardial conductive tissue. The above publications [150-5] quote a large number of relevant references. 

PROCAINAMIDE MUSCLE RELAXANTS-DEPOLARISING Possibility oft neuromuscular blockade Uncertain procainamide may 1 plasma cholinesterase levels Be aware of the possibility of a prolonged effect of suxamethonium when administered to patients taking procainamide... 

The neuromuscular blockade due to suxamethonium (succinyl-choline) can be increased and prolonged by lidocaine, procaine and possibly procainamide. These local anaesthetics all have some neuromuscular blocking activity and may theoretically also enhance the block produced by competitive neuromuscular blockers. Increased toxicity occurred when mivacurium and prilocaine were given together for regional anaesthesia. 

Procainamide has been reported to increase the effects of suxamethonium in animals, increase muscle weakness in a myasthenic patient, and reduce plasma cholinesterase activity in healthy subjects. An animal study demonstrated potentiation of the neuromuscular blocking effect of tubocurarine by lidocaine alone and combined with antibiotics having neuromuscular blocking activity (neomycin or polymyxin B). ... 

Uncertain. Some local anaesthetics (ester-type ) such as procaine appear to inhibit plasma cholinesterase, which might prolong the activity of suxamethonium. There may additionally be competition between suxamethonium and procaine for hydrolysis by plasma cholinesterase, which metabolises them both. These effects are particularly important in patients with abnormal plasma cholinesterase. Therapeutic procainamide plasma concentrations of 5 to 10 micrograms/mL have been found to inhibit cholinesterase activity by 19 to 32%. ... 

Despite the potential for an interaction between suxamethonium and procainamide, no marked interaction has yet been reported. Nevertheless be aware that some increase in the neuromuscular blocking effects is possible. 

Cuthbert MF. The effect of quinidine and procainamide on the neurom uscular blockii action of suxamethonium. BrJ Anaesth (1966) 38,775-9. 

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