Influence of metoclopramide on plasma cholinesterase and duration of action of mivacurium.

Mivacurium is metabolized by plasma cholinesterase (PCHE). Metoclopramide inhibits PCHE in vitro and in vivo. We have assessed the effect of metoclopramide on duration of action of mivacurium and measured PCHE at baseline and at the time of maximal block. In a randomized, double-blind study, 30 patients received metoclopramide 0.15 mg kg-1 i.v. or saline, followed by propofol anaesthesia and mivacurium 0.15 mg kg-1. Using a TOF-Guard accelerometer, times to recovery of TI to 25%, 75% and 90% were 13.4, 19.3 and 21.9 min in the saline group and 17.8, 25.3 and 28.8 min in the metoclopramide group (P < 0.01, P < 0.05, P < 0.05, respectively). There were no differences in onset time or recovery index between the groups. PCHE activity at the time of maximum block decreased within each group (P < 0.01) but there was no difference between groups. In a second biochemical study of eight patients, a small decrease in PCHE activity was detected after metoclopramide 0.15 mg kg-1, but before administration of mivacurium (P < 0.025). We conclude that metoclopramide prolongs the duration of action of mivacurium.