A new validated high‐performance liquid chromatography method for the determination of regorafenib in rat plasma: Application for pharmacokinetic study

This study reports a rapid and sensitive reversed‐phase high‐performance liquid chromatography method with ultraviolet detection for the determination of regorafenib (REG) in rat plasma. For the extraction of REG from plasma and the precipitation of plasma proteins, a rapid one‐step precipitation method was performed with methanol. The separation was performed in a methanol‐water mixture (80:20, v:v) mobile phase system with a C18 column and monitored at a wavelength of 258 nm. Nilotinib was used as an internal standard. The linear dynamic range of REG was determined between 5 and 500 ng/mL in standard solution and plasma. The limit of detection of REG from the standard solution was found to be 1.23 ng/mL and the limit of quantitation was 3.73 ng/mL. The limit of detection of REG from plasma was found to be 1.55 ng/mL and the limit of quantitation was 4.70 ng/mL. Regorafenib was administered at 5 mg/kg to 10 healthy male Sprague Dawley rats, and pharmacokinetic results were evaluated. It exhibited a high recovery of 93.82% in plasma. Due to ease of sample preparation, high susceptibility, specificity, and certainty, the described method can be used successfully in the quantification of REG in in‐vivo plasma and in routine analyses in clinical laboratories.