A novel TLC method for the concurrent bioanalysis of methotrexate and etoricoxib in spiked human plasma with comprehensive sustainability evaluation

Methotrexate (MTX) is the primary disease-modifying agent used in the treatment of rheumatoid arthritis, with etoricoxib (ETO) and other selective COX-2 inhibitors serving as adjuvant therapy to alleviate pain and inflammation. However, ETO may impede the kidney clearance of MTX, raising its plasma levels and the probability of dose-dependent toxicity. Therefore, a novel, FDA-validated TLC method was developed to simultaneously determine MTX and ETO in spiked human plasma in a single chromatographic run. The best separation was achieved using a mobile phase of methanol and isopropanol (9.5:0.5 v/v), with cyproheptadine as an internal standard and detection at 285 nm. The R f values were plasma (0.04), cyproheptadine (0.36), methotrexate (0.73), and etoricoxib (0.83), showing good resolution. The method was linear over the ranges 0.2–0.9 µg band −1 and 0.5–1.1 µg band −1 for MTX and ETO, respectively. The method was also validated in compliance with the main FDA bioanalytical criteria in spiked human plasma, showing acceptable accuracy and precision. The sustainability of the proposed method was assessed using a range of evaluation tools, namely MoGAPI, AGSA, CaFRI, EPPI, BAGI, and SAMI, collectively confirming that the method provides a green, simple, rapid, and inexpensive option for quality control laboratories, especially those with limited resources. Furthermore, a web-based tool was employed to assess the potential for CYP-mediated drug-drug interactions between MTX and ETO. The findings indicated a low risk of interaction.