Sugammadex (SDX), a neuromuscular blocking-reversal agent, quickly reverses neuromuscular blockade induced by rocuronium (RCR). SDX dosage is set according to the state of neuromuscular blockade determined with a neuromuscular monitoring device. However, in clinical situations, such a devise is not frequently used. Here, we report construction of a method for theoretically setting SDX dose by which the optimum reverse time (RT) can be obtained for individual patients even when the device is not available. The subjects were 42 adult female patients who underwent laparoscopic surgery from 1 August 2015 to 31 March 2016, during which RCR and SDX were administered. We formulated an equation for theoretically calculating the RCR residual ratio (RR) in blood after SDX administration. Furthermore, we examined the relationship between RR and RT. Based on the results obtained, we developed a method for predicting RT using RR. We excluded 1 subject as the RT value was detected as an outlier in our analysis. Multiple regression analysis was performed using standard body weight, serum creatinine, total bilirubin, and RR as explanatory variables. The number of subjects with a prediction error of RT within 1 min was 36 (87.8%) of 41 in multiple regression analysis. We could predict RT following SDX administration by using the RT prediction expression with RR obtained for subjects administered RCR during the surgery. Furthermore, our results suggest that the SDX dose able to achieve optimum RT may be set prior to surgery on the basis of the present methodology.Key words sugammadex; rocuronium; gynecological laparoscopic surgery; reverse time prediction It has been reported that the period of hospitalization could be reduced, and patient QOL and surgical results improved by use of laparoscopic surgery as compared to a laparotomy in the field of gynecology.1-3) With laparoscopic surgery, use of a neuromuscular blocking agent is required for expanding the surgical field and preventing sudden body motion.4) Rocuronium (RCR), a widely used neuromuscular blocking agent, is known to have a reduced bradycardia effect 5) when used for gynecological laparoscopic surgery and less bioaccumulation because an active metabolite is absent, 5,6) and a significantly shorter time of onset of action is available and reduced time for completing tracheal intubation can be achieved.6-14) Meanwhile, at the completion of the surgery, sugammadex (SDX) is often used as a neuromuscular blocking-reversal agent for shortening the time of recovery from muscle relaxation and preventing a residual relaxation effect.15) SDX, a derivative of γ-cyclodextrin, has also be reported to reverse neuromuscular blockade more quickly and safety than conventional cholinesterase inhibitors by forming an inclusion compound with RCR in blood to reduce the concentration of the neuromuscular blocking agent in the neuromuscular junction. 16,17) The dose of SDX is set according to the state of neuromuscular blockade producing muscle relaxation, which can be determined with a neu...