Spontaneous recovery of a gantacurium-induced neuromuscular block is rapid. However, as gantacurium is a non-depolarizing neuromuscular blocking drug, gantacurium can be reversed with cholinesterase inhibitors [
12]. As the spontaneous recovery of gantacurium is rapid, the most suitable drug for reversal is edrophonium as the peak effect of this reversal drug is less than 2 min. In humans, edrophonium was able to decrease the reversal time of a gantacurium-induced neuromuscular block at 10% recovery of T1 to a train-of-four ratio ≥ 0.90 to 3.8 min. Spontaneous reversal of the same neuromuscular block occurred in 5.7 min. Neostigmine as result of its peak effect at 7–11 min is not suitable for reversal of a gantacurium-induced neuromuscular block [
12].
Gantacurium is, due to its unique metabolism, rapidly inactivated by cysteine adduction and alkaline hydrolysis. One of these routes of inactivation is adduction of the amino acid cysteine to the molecule of gantacurium. Cysteine exists as
l- and
d-enantiomers and the
l-enantiomer is suitable as a reversal drug for the new class of neuromuscular blocking drugs: the asymmetric mixed-onium chlorofumarates [
12‐
14,
15••]. Administration of intravenous
l-cysteine results in replacement of chlorine by cysteine whereafter a heterocyclic ring is formed which cannot longer interact with the postjunctional acetylcholine receptor and the neuromuscular block can be reversed.
l-Cysteine (-hydrochloric) is acidic and commonly administered in humans as an essential component of parental nutrition.
l-Cysteine given in as a bolus dose of 10–50 mg/kg for reversal of neuromuscular block is not known to have any toxicity [
12‐
14,
15••]. Therefore, gantacurium can also be reversed by administration of
l-cysteine. In preclinical studies,
l-cysteine administration after 8× ED
95 of gantacurium resulted in a decrease in recovery times (to a train-of-four ratio ≥ 0.90) by 2 min. When
l-cysteine was administered just 1 min after 8× ED95 of gantacurium, the recovery to a train-of-four ratio ≥ 0.90 was shortened by 6 min [
12]. No signs of residual neuromuscular blockade or recurarization were observed [
12]. To date, no clinical studies were conducted in which
l-cysteine reversal was investigated.