Simultaneous determination of Gemcitabine Hydrochloride and Irinotecan Hydrochloride in rat plasma by high performance liquid chromatography-diode array detector

This comunication reports a easy and quick HPLC-PDA method for the simultaneous analysis of Irinotecan Hydrochloride and Gemcitabine Hydrochloride in rat plasma samples both after single drug administration and drugs association. Gemcitabine Hydrochloride is commonly administered to treat non-small cell lung cancer (NSCLC), pancreatic adenocarcinoma, and in combination with paclitaxel for the treatment of breast cancer in the metastatic phase. Additionally Irinotecan Hydrochloride was used to treat colorectal cancer (CRC), gynecological cancers, carcinomas, non-small cell and small cell lung cancer. The drugs were detected simultaneously by using a Zorbax Extend C-18 column (250 mm × 4.6 mm; 5 m particle size) in gradient elution mode. The chromatographic analysis was performed in 15 minutes. The analytical method was calibrated and validated from 0.1 to 18 g/mL for both drugs. Rat plasma was used as biological samples during the analysis; while the 3-methylxanthine was used as internal standard. The performance of analytical method was further tested in rat plasma samples collected after single dose administration of drug or their association. Results demonstrated that HPLC-PDA method allows to detect the drugs in the range of concentrations herein reported and the analytical method is accurate and selective. The limit of quantification of the method was 0.1 g/mL. These values are similar or little higher to data published in literature, which are performed using sophisticated and expensive detectors such as mass spectrometer, and wich consider merely only one drug and not their association. The weighted-matrix matched standard curves showed a good linearity until 18 g/mL. The parallelism tests were also performed to evaluate if over-range samples can be analyzed after dilution, without affecting the performance of validated method. The intra- and inter-day precision (RSD%) values were ≤7.14% and ≤11.5%, respectively, for the full range of analysis. The intra- and inter-day trueness (Bias%) values ranged from -11.5% to 1.70% for the two drugs. At the best of our knowledge, this is the first HPLC-PDA method which allows to detect simultaneously Irinotecan Hydrochloride and Gemcitabine Hydrochloride in rat plasma, both after single and drugs association administration in order to evaluate how can interact and modify the pharmacokinetic parameters