A rapid and sensitive determination of hypoxic radiosensitizer agent nimorazole in rat plasma by LC-MS/MS and its application to a pharmacokinetic study.

A highly sensitive, accurate and robust LC-MS/MS method was developed and validated for determination of nimorazole (NMZ) in rat plasma using metronidazole (MNZ) as internal standard (IS). The analyte and IS were extracted from plasma by precipitating protein with acetonitrile and were chromatographed using an Agilent Poroshell 120, EC-C18 column. The mobile phase was composed of a mixture of acetonitrile and 0.1 % formic acid (85:15 v/v). The total run time was 1.5 min and injection volume was 5 µL. Multiple reaction monitoring mode using the transitions of m/z 227.1 → m/z 114.0 for MNZ and m/z 172.10 → m/z 128.1 for IS were monitored on a triple quadrupole mass spectrometer, operating in positive ion mode. The calibration curve was linear in the range of 0.25-200 ng/mL (r(2) > 0.9996) and the lower limit of quantification was 0.25 ng/mL in the rat plasma samples. Recoveries of NMZ ranged between 88.05 and 95.25%. The precision (intra-day and inter-day) and accuracy of the quality control samples were 1.25-8.20% and -2.50-3.10, respectively. The analyte and IS were found to be stable during all sample storage and analysis procedures. The LC-MS/MS method described here was validated and successfully applied to pharmacokinetic study in rats.

Study of the population pharmacokinetic characteristics of nimorazole in head and neck cancer patients treated in the DAHANCA-5 trial.

AIMS: To study the pharmacokinetic characteristics of the hypoxic radiosensitiser nimorazole in patients with head and neck squamous cell carcinoma. MATERIALS AND METHODS: The pharmacokinetics of the hypoxic radiosensitiser nimorazole were studied in 63 patients treated in the DAHANCA-5 trial. After the first day of treatment, serial venous blood samples were taken and plasma concentrations of nimorazole measured by high pressure liquid chromatography (HPLC). Plasma concentration profiles were subjected to non-compartmental pharmacokinetic analysis using validated PC-based software. The different pharmacokinetic parameters were calculated and correlated with the different patient- and treatment-related variables. RESULTS: HPLC measurements showed a linear relationship between peak plasma concentration and administered dose. The mean peak concentration adjusted for dose (in g/m(2)) was 32.2 ± 0.9 µg/ml. The time of peak concentration ranged between 30 and 180 min (median 60 min). Plasma elimination occurred with a mean half-life of 3.35 ± 0.09 h and was not significantly altered as a function of dose. There was a well-established linear-linear relationship between area under the concentration-time curve (AUC; mean 191 ± 6 µg·h/ml) and administered dose, especially when expressed as g/m(2). The mean apparent volume of distribution was 0.77 ± 0.02 l/kg. A statistically significant longer elimination half-life in men relative to women (mean difference 0.40 h; 95% confidence interval 0.77-0.03; P 0.03) was detected. Nimorazole was well tolerated; with 67% of patients reporting no toxicity; nausea/vomiting was the most reported toxicity in the remaining patients. CONCLUSION: The study supports the current nimorazole dose scheduling in patients.