Green HPLC-PDA method for simultaneous determination of linagliptin and cefixime with pharmacokinetic application in...

Many individuals with diabetes have compromised immune systems and reduced peripheral sensation, making them susceptible to infections. As a result, combination therapy involving antidiabetic drugs and antibiotics has become essential. A newly introduced combination of the antidiabetic drug linagliptin (LIN) and the third-generation cephalosporin antibiotic cefixime (CEF) has been recommended to combat infections in diabetic patients.To optimize therapeutic efficacy and minimize adverse effects associated with this combination therapy, a reliable analytical method was essential for pharmacokinetic analysis and therapeutic drug monitoring. This study present, for the first time, a green high-performance liquid chromatographic method with photodiode array detection (HPLC-PDA) for the simultaneous determination of LIN and CEF in plasma samples. Chromatographic separation was achieved using a Symmetry C₁₈ column (250 mm × 4.6 mm, 5 μm particle size) under isocratic elution with a mobile phase consisting of 20 mM sodium phosphate (pH 4.3, adjusted with orthophosphoric acid) and methanol (50:50, v/v). The flow rate was set at 0.8 mLmin^- 1, with a total run time of 12 min. The injection volume was 20 µL and the detection was performed at 230 nm. The method demonstrated linearity over a range of 50-2000 ng mL^-1for both LIN and CEF, with limits of detection (LOD) of 24 and 21 ngmL⁻¹ and limits of quantitation (LOQ) of 43 and 45 ngmL⁻¹ for LIN and CEF, respectively. Validation parameters complied with ICH M10 bioanalytical guidelines. Additionally, the method was successfully applied to a pharmacokinetic study comparing drugs efficacy when administered alone versus concurrently. The results demonstrated that co-administration of LIN and CEF significantly altered their bioavailability: LIN C_max increased by 63.2% and AUC increased by 134.2%, while CEF C_max decreased by 27.3% and AUC decreased by 23.3%, indicating a bidirectional pharmacokinetic interaction, and underscoring the need for careful monitoring during combination therapy.The greenness of the proposed HPLC-PDA method was evaluated using four metric tools and the findings confirmed the method's minimal environmental impact. In conclusion, the developed HPLC-PDA method not only provides a reliable tool for therapeutic drug monitoring in clinical practice but also establishes a robust framework for future investigations into drug-drug interactions in human therapeutics.