The use of anticholinesterases to reverse residual neuromuscular block is efficacious only if recovery is already established. It was originally advised that at least the second twitch (T2) of the train-of-four response should be detectable before neostigmine is administered. Even in these circumstances, the full effect of anticholinesterases takes up to 10 min to achieve. Anticholinesterases also have muscarinic side-effects that require an antimuscarinic to be administered concomitantly. An ideal reversal agent could be given at any time after the administration of a neuromuscular blocking agent (NMBA), and should have no muscarinic side-effects. The gamma cyclodextrin, sugammadex, has been demonstrated to effectively antagonize even profound block produced by the aminosteroid NMBAs, rocuronium and vecuronium, by chelating them. The complex is then excreted in the urine. Sugammadex is ineffective in antagonizing the benzylisoquinolinium NMBAs. The dose should be adjusted according to the degree of residual block: sugammadex 16 mg kg(-1) for immediate reversal; 4-8 mg kg(-1) for antagonizing profound block (post-tetanic count 1-2); and 2 mg kg(-1) to antagonize moderate block (when T2 is detectable). As yet, the extent of any side-effects that may occur with this new antagonist is not fully known, although rarely adverse cardiovascular effects (hypotension, hypertension, prolonged QT interval) have already been reported.