The sodium salt form of the biologically inert, selective relaxant binding agent (SRBA) sugammadex, a modified, anionic gamma cyclodextrin derivative containing a hydrophilic exterior and a hydrophobic core, with neuromuscular blocking drug (NMBD) reversal activity. Upon administration, the negatively charged carboxyl-thio-ether groups of sugammadex selectively and reversibly bind to the positively charged quaternary nitrogen of a steroidal NMBD, which was administered at an earlier time for anesthetic purposes. The encapsulation of the NMBD by sugammadex blocks its ability to bind to nicotinic receptors in the neuromuscular junction and thereby reverses the NMBD-induced neuromuscular blockade. Sugammadex binds rocuronium, vecuronium, and to a lesser extent pancuronium.