Background: Remimazolam besylate is a novel short-acting benzodiazepine. An appropriate pharmacokinetic model of remimazolam is desirable in anesthesia practice. The aim of the study was to develop a pharmacokinetic model using plasma samples from patients anesthetized with remimazolam. Influence of patient characteristics, context-sensitive decrement-times, and dose regimens were also examined.
Methods: Data were obtained from four trials on patients, and seven trials on healthy volunteers. The characteristics of 416 male and 246 female subjects were as follows: age, 18-93 years; body weight, 34-149 kg; and American Society of Anesthesiologists physical status (ASA-PS), I-IV. 2231 arterial and 3200 venous samples were used for the final model. The equilibration rate constant between arterial plasma and effect-site was estimated using the concept of time to peak effect. The final model was used to generate context-sensitive decrement times and dose regimens for general anesthesia.
Results: A three-compartment model plus virtual venous compartment with allometric scaling of adjusted body weight (ABW), age, sex, and ASA-PS as covariates were selected as the final model. Elimination clearance was lower in males, and in subjects with higher ABW and ASA-PS scores. Approximately 10% or 20% higher dose rate was necessary in females than in males or ASA-PS I/II than III/IV patient. The context-sensitive half-time for effect-site concentration in a 55-year-old, 70-kg, 170-cm male or female ASA-PS I/II patient after > 6-h infusion was 16.7 or 15.9 min.
Conclusion: Remimazolam pharmacokinetic model for general anesthesia was successfully developed. ABW, ASA-PS, and sex has a considerable impact on the remimazolam concentration.
Keywords: Benzodiazepine; Effect-site concentration; General anesthetic; Pharmacokinetics; Remimazolam; Three-compartment model.
© 2022. The Author(s) under exclusive licence to Japanese Society of Anesthesiologists.