Effect of oral antihistamine premedication on mivacurium-induced histamine release and side effects

In this randomized, double-blind, placebo-controlled study, we have examined histamine release, haemodynamic and cutaneous effects of mivacurium administered in low (0.105 mg kg-1 = 1.5 x ED95) and high (0.21 mg kg-1 = 3 x ED95) doses and assessed if oral pretreatment with H1/H2 antagonists would blunt the effects of mivacurium-induced histamine release. Patients received either ranitidine 300 mg and dimethindene 0.1 mg kg-1 (H1 blocker) or placebo, orally 1 h before induction of anaesthesia. Twelve patients were allocated to each group. Although plasma concentrations of histamine increased significantly in three patients in the placebo group given low-dose mivacurium, the mean value for the group was unchanged. Plasma concentrations of histamine increased significantly in five patients in the placebo group after high-dose mivacurium and the mean value was increased. There was no consistent correlation between haemodynamic changes, cutaneous manifestations and histamine concentrations. Significant cardiovascular reactions occurred in six patients in the placebo groups and in only one patient treated with antihistamines.