High-performance liquid chromatographic method for the determination of sorafenib in human serum and peritoneal fluid.

PURPOSE: Sorafenib is recommended for therapy of advanced hepatocellular carcinoma and renal cell carcinoma. Preclinical data indicate a relation between dose and antitumor efficacy. In clinical trials, adverse events improve after dose reduction suggesting a dose-dependent toxicity. Given dose has a direct impact on the drug serum concentration, but the latter also can be influenced by multiple factors, including interaction and metabolisation. To enable the investigation of concentration-related effects, an easy and sensitive assay for sorafenib drug monitoring is essential. METHODS: A high-performance liquid chromatography (HPLC) analysis involving an extraction with diethyl ether followed by separation on a Pinnacle™ DB C18 column and quantitation by UV absorbance at 260 nm was established. Sorafenib concentrations in samples of serum and peritoneal fluid have been determined. RESULTS: The assay was validated for serum samples and is linear over the concentration range of 100-5,000 ng/ml with a determination coefficient of >0.999. The limit of detection is 0.25 ng/ml. The intra- and inter-day coefficients of variation were below 3.03%. Sorafenib recovery in spiked probes of peritoneal fluid was above 85%. Sorafenib concentrations in 44 serum samples and 14 probes of peritoneal fluid have been determined with a mean of 3,328 and 1,380 ng/ml, respectively (standard deviation 2,267 and 659 ng/ml). CONCLUSIONS: A sensitive and selective HPLC method for the determination of sorafenib in human serum was developed and also verified for peritoneal fluid. This method provides a useful tool for pharmacokinetic investigations as well as for therapeutic drug monitoring of sorafenib.