RESUMEN
BACKGROUND: Previous studies examining the pharmacodynamic effects of succinylcholine(SCC) on subsequent doses of nondepolarizing muscle relaxants showed potentiation with resultant prolonged respiratory depression or no interaction at all. The interaction between SCC and mivacurium especially has not been investigated in animal and other clinical studies. METHODS: The pharmacodynamic effects of SCC on mivacurium-induced neuromuscular blockade and its reversal were investigated in 10 cats of either sex using the anterior tibialis muscle-sciatic nerve preparation. RESULTS: There was no significant difference at the onset of mivacurium neummuscular blockade between the control group(1.81+/-0.48 min) and SCC-pretreated group(1.86+/-1.04 min). However the duration of action of mivacurium neuromuscular blockade was significantly longer in the SCC-pretreated group(33.08+/-19.13 min) than that of the control group(10.65+/-2.45 min). In the control group recovery indices(RI) were 2.35+/-1.01 min and 0.68+/-0.30 min at spontaneous recovery and antagonism with neostigmine, respectively and in the SCC-pretreated group they were 6.88+/-2.42 min and 1.90+/-0.64 min. RI were significantly shortened by antagonism with neostigmine whether or not SCC was pretreated. In the SCC-pretreated group, RI were significantly longer than in the control group at spontaneous recovery and antagonism with neostigmine. But the maximal recovery and antagonism effect were 100% in all cases. There was no sigriificant difference in the train-of-four ratios measured after antagonism with neostigmine between the control group(0.91+/-0.01) and the SCC-pretreated group(0.93+/-0.06). CONCLUSIONS: The prior administration of SCC prolonged the duration of mivacurium-induced neuromuscular blockade and delayed recovery but had no influence in antagonism with neostigmine in cats.