The introduction of muscle relaxants, more appropriately called neuromuscular blocking agents, into clinical practice in 1942 was an important milestone in the history of anesthesia (Donati F, Neuromuscular blocking agents. In: Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Ortega R, Stock MC, eds. Clinical Anesthesia. Philadelphia: Lippincott Williams & Wilkins; 2013:523–560). Neuromuscular blocking drugs (NMBDs) are used to improve conditions for tracheal intubation, provide immobility during surgery, and facilitate mechanical anesthesia. The incidence of awareness appears to be greater when neuromuscular blocking agents are used (which reflects too little anesthetic being administered). The effects of NMBDs must have worn off or be reversed before the patient regains consciousness (reversal of blockade is required in most patients). Residual paralysis is still a problem despite the availability of shorter-acting NMBDs and widespread use of neuromuscular monitoring (the threshold for complete neuromuscular recovery is a train-of-four [TOF] ratio of 0.9).