Time course of action of sugammadex (Org 25969) on rocuronium-induced block in the Rhesus monkey, using a simple model of equilibration of complex formation

Background. Reversal of neuromuscular block can be accomplished by chemical encapsulation of rocuronium by sugammadex (Org 25969), a synthetic gamma-cyclodextrin derivative. The present study determined the time course of the reversal action of sugammadex on rocuronium-induced block in the anaesthetized Rhesus monkey using train-of-four stimulation. Methods. A bolus injection of rocuronium 100 mu g kg(-1) (about 1xED(90)) was given to determine the degree of neuromuscular block reached by this dose. After complete spontaneous recovery, a rapid bolus injection of sugammadex, 1 mg kg(-1), was given and at different time intervals (15, 30 or 60 min, in three different experiments) the effect of another rocuronium bolus injection of 100 mu g kg(-1) was determined. Results. Injection of the first dose of rocuronium resulted in a mean neuromuscular block (depression of first twitch) of 93 (sem=1.6)%. Fifteen minutes after injection of sugammadex the same rocuronium dose resulted in 17% (sem=5.6) block. After 30 and 60 min these maximum blocks amounted to 49% (sem=7.6) and 79% (sem=4.2), respectively. The estimated half-life of sugammadex in Rhesus monkey is 30 (sem=4.9) min. Conclusions. The half-life of sugammadex (Org 25969), a new fast and efficient reversal agent for rocuronium-induced block, is relatively short in the Rhesus monkey, implying the possibility to perform neuromuscular block by rocuronium shortly after reversal of a prior block. In translation to the human situation differences in rocuronium sensitivity and kinetics should be taken into account.