Alphadione and minaxolone pharmacokinetics

Althesin (alphaxalone: alphadolone acetate) and the new water-soluble steroid intravenous anaesthetic agent minaxolone have been administered by continuous infusion to supplement nitrous oxide: oxygen anaesthesia in 20 patients. Plasma drug concentrations were estimated in blood samples taken during and following cessation of the infusion. In both group (Althesin: n = 11, minaxolone: n = 9), there was no evidence of drug accumulation within the plasma. The decay in the plasma drug concentrations after the infusion could be fitted to a bi-exponential equation, indicating that the steroids were distributed according to an open two-compartment pharmacokinetic model. The prolonged recovery following minaxolone may be related to its water-solubility, and to a larger volume of distribution of the drug. Studies gas chromatography: mass spectrometry to analyse samples of blood and urine have confirmed than Althesin and minaloxone both undergo biotransformation in the body. Hepatic conjugation to glucuronic acid is of importance in the excretion of the lipophilic agent, Althesin.