To determine the neuromuscular effect of mivacurium and its reversals in combination with gentamicin or magnesium, pharmacodynamic studies were done using a common peroneal nerve-anterior tibialis muscle preparation in 18, either sex, adult cats(weight, 2.5-4 kg). The ED50 or ED95 of mivacurium obtained by the cumulative dose-response study was 28.2+/-8.5 or 44.7+/-7.3 ug/kg, respectively. The onset of mivacurium under the pretreatment of magnesium (2.8+/-0.4 min.) was slower than that under the pretreatment of gentamicin (1.8+/-0.5 min.). The duration of mivacurium was prolonged. significantly with either gentamicin or magnesium compared to mivacurium alone. However, neostigmine facilitated the recovery of the neuromuscular block induced by mivacurium, even if gentamicin or magnesium was previously treated, and the antagonism effects of neostigmine and spontaneous recovery were always 100%. These results suggest that the neuromuscular blocking actions of mivacurium were potentiated by the pretreatment of gentamicin or magnesium, and mivacurium-induced neuromuscular block with gentamicin or magnesium was reversed completely.
Adult ; Animals ; Cats* ; Gentamicins* ; Humans ; Magnesium* ; Neostigmine ; Neuromuscular Agents ; Neuromuscular Blockade*