Neuromuscular block by suxamethonium following treatment with histamine type 2 antagonists or metoclopramide

We have examined the effect of preoperative i.v. administration of three different histamine type 2 (H2) antagonists (cimetidine 400 mg, ranitidine 80 mg and famotidine 20 mg) or metoclopramide 10 mg i.v. on the duration of neuromuscular block produced by an intubating dose (1 mg kg-1) of suxamethonium. The study was conducted blindly in 70 post partum patients, weighing between 45 and 120 kg, scheduled for tubal ligation. The duration of neuromuscular block following suxamethonium was measured from a chart recording of train-of-four (TOF) electromyographic responses. The time from onset of 95% block to 25% recovery ("block time") was not significantly different between the groups receiving cimetidine (A), ranitidine (B), famotidine (C), and control (E). However, there was prolongation of neuromuscular block in patients receiving suxamethonium and metoclopramide (D).