Pharmacokinetics of colistin in cerebrospinal fluid after intraventricular administration alone in intracranial infections

The aim of this study was to investigate the pharmacokinetics of colistin in cerebrospinal fluid (CSF) after intraventricular (IVT) administration of colistin methanesulfonate (CMS) for central nervous system (CNS) infections caused by multidrug-resistant Gram-negative bacteria. Ten patients with CNS infection were treated with CMS (active substance colistin equivalent to 100 000 units, every 24 h) by IVT administration. After 3 days of treatment, the concentration of colistin in the CSF was determined by selective ultra-performance liquid chromatography (UPLC) at 2, 4, 6, 8, 12 and 24 h after CMS administration. A pharmacokinetic analysis was performed using Phoenix WinNonlin. Following IVT administration of CMS, the estimated colistin apparent CSF half-life (t_1/2) was 10.46 ± 6.98 h, the average peak colistin concentration (C_max) was 16.95 ± 7.39 μg/mL and the average time to peak concentration (T_max) was 4.6 ± 0.97 h. The measured trough concentration (C_min; colistin concentration in CSF at 24 h after administration of CMS) was 1.12–8.33 μg/mL and the average C_min was 2.91 ± 2.11 μg/mL. CSF concentrations of colistin were above the minimum inhibitory concentration (MIC) of 0.5 μg/mL at 24 h after IVT administration in all patients. Microbiological cure was observed in all patients. In conclusion, this is the first study of colistin pharmacokinetics in CSF after IVT administration alone in patients with CNS infection. It provides essential data for designing relatively safe and effective CMS dosing regimens.