A miniature pig model of pharmacological tolerance to long-term sedation with the intravenous benzodiazepines; midazolam and remimazolam.

As a new and ultra fast-acting IV benzodiazepine, pharmacological tolerance may be anticipated during long-term treatment with remimazolam e.g. in intensive care. In this context, tolerance is particularly relevant for withdrawal syndrome. However, apart from primates, existing models of sedative tolerance are unsuitable for remimazolam due to its excessive metabolic clearance (i.e. in rodents) or paradoxical responses (in dogs). Pigs are a well-established model species, especially for in-vivo drug safety studies, and appear a well suited as model for evaluation of remimazolam. In a series of experiments from dose-range-finding bolus and infusion studies through to 28-day continuous level sedation, we established a viable model of intravenous benzodiazepine sedation in NIBS micropigs to compare tolerance development during 28 days sedation with either midazolam or remimazolam. Dose increases after 28 days were lower for remimazolam (0 to 3-fold) than for midazolam (2 to 4-fold) and recovery times were approximately 40% faster for remimazolam vs midazolam. Tolerance to remimazolam is therefore likely in long-term human sedation and may be less than that seen for midazolam.