Fig. 3. Comparative antagonism of gantacurium (0.5 mg/kg or ∼5 × ED⁹⁵) by edrophonium (1.0 mg/kg with atropine 0.05 mg/kg) or l-cysteine (10 mg/kg). Gantacurium was injected at t = 0. Antagonist was given at the beginning of recovery at 2% twitch height (standard antagonism, B ); or at 1 min after gantacurium administration (immediate antagonism, A ). Antagonism by l-cysteine is faster than edrophonium at 2% twitch and is equally rapid at either 2% twitch or at 1 min after gantacurium (P < 0.05). Antagonism by l-cysteine at 1 min is significantly faster (P < 0.001) than edrophonium, which shifts the dose–duration curve to the left by only ∼2 min. Curves show summarized data from experiments in anesthetized rhesus monkeys in which twitch of the extensor digitorum was elicited at 0.15 Hz (see also fig. 4).