NEUROMUSCULAR BLOCKING ACTION OF SUXAMETHONIUM AFTER ANTAGONISM OF VECURONIUM BY EDROPHONIUM, PYRIDOSTIGMINE OR NEOSTIGMINE

The reported effects of edrophonium on a subsequent dose of suxamethon ium are variable and the effects of pyridostigmine have not been evalu ated extensively. We have studied this interaction in patients anaesth etized with propofol and sufentanil. After recovery from an initial bo lus (1 mg kg(-1)) of suxamethonium, vecuronium was infused to produce 75% block. After 30 min, the infusion was discontinued and saline 5 ml , edrophonium 0.75 mg kg(-1), pyridostigmine 0.24 mg kg(-1) or neostig mine 0.05 mg kg(-1) was given. Fifteen minutes later the mean duration s of a second bolus of suxamethonium were: 10.5 (SD 3.9) min (saline), 10.9 (3.7) min (edrophonium), 18.7 (5.4) min (pyridostigmine) and 23. 8 (7.4) min (neostigmine). Corresponding plasma cholinesterase activit ies (percentage of baseline) were: 91 (18), 87 (9), 21 (10) and 52 (26 ). When both treatment groups and individual patients were compared, t he changes in duration of action did not correlate with changes in cho linesterase activity. These data suggest that other mechanisms in addi tion to cholinesterase inhibition may contribute to this drug interact ion.