Objectives: The aim of this study was to evaluate the effect of colistin methanesulphonate (CMS) dose on CMS and colistin pharmacokinetics in rats.
Methods: Three rats per group received an intravenous bolus of CMS at a dose of 5, 15, 30, 60 or 120 mg/kg. Arterial blood samples were drawn at 0, 5, 15, 30, 60, 90, 120, 150 and 180 min. CMS and colistin plasma concentrations were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The pharmacokinetic parameters of CMS and colistin were calculated by non-compartmental analysis.
Results: Linear relationships were observed between CMS and colistin AUCs to infinity and CMS doses, as well as between CMS and colistin C(max) and CMS doses.
Conclusions: CMS and colistin pharmacokinetics were linear for a range of colistin concentrations covering the range of values encountered and recommended in patients even during treatment with higher doses.