List the proper doses of muscle relaxant antagonists and their duration of action.
Recommended “reversal” dosages depend on the depth of neuromuscular blockade and the particular muscle relaxant employed. Neostigmine is 5 times more potent than pyridostigmine and about 12 times more potent than edrophonium. Typical doses for neostigmine, pyridostig-mine, and edrophonium are 0.04–0.06 mg/kg, 0.21 mg/kg, and 0.5 mg/kg, respectively (Table 25.1). These drugs offer differing onset times. Edrophonium has the most rapid onset time, exerting a peak effect in slightly over 1 minute. Neostigmine and pyridostigmine have slower onsets, exert-ing their peak effects in 6 and 15 minutes, respectively. All three commonly used acetylcholinesterase inhibitors are of sufficient duration to antagonize nondepolarizing neuro-muscular blockade secondary to long- or intermediate-acting drugs provided the degree of residual blockade is moderate (detectable responses to train-of-four (TOF) stimulation).
Edrophonium, even when used in large doses (0.5–1 mg/ kg), is an unreliable antagonist of deep neuromuscular blockade (T1/TC = 10–25%) induced by long-acting mus-cle relaxants (tubocurarine, pancuronium, pipecuronium, or doxacurium). When deep neuromuscular blockade is present, edrophonium should not be used as an antagonist.