Increased effect by anaesth agents eg, enflurane, isoflurane, halothane & ketamine; other non-depolarising neuromuscular blocking agents or by other drugs eg, antibiotics, antiarrhythmics, diuretics, Mg & lithium salts & ganglion blocking drugs. Various antibiotics, β-blockers, antiarrhythmics, antirheumatic drugs, trimetaphan, chlorpromazine, steroids, phenytoin & lithium may aggravate or unmask latent myasthenia gravis or induce a myasthenic syndrome. Decreased effect w/ chronic administration of phenytoin or carbamazepine. Treatment w/ anticholinesterase eg, donepezil may shorten duration & diminish the magnitude of neuromuscular blockade. Administration of suxamethonium to prolong the effects of non-depolarising neuromuscular blocking agents may result in a prolonged & complex block which can be difficult to reverse w/ anticholinesterases.