Eco-friendly RP-HPLC method for concurrent estimation of a promising combination of methocarbamol and etoricoxib in rat plasma

An innovative green reverse phase high-performance liquid chromatography method was developed and validated for the concurrent quantification of methocarbamol (MTC) and etoricoxib (ETC) in rat plasma using diclofenac potassium as an internal standard. This method introduces significant advancements over existing chromatographic techniques, including a rapid analysis time (8-min run time) and cost efficiency due to low solvent consumption (total solvent use of 444 mL), achieved through optimized chromatographic conditions. The method employs a Hypersil BDS C8 column (4.6 mm × 250 mm, 5 µm) with an isocratic mobile phase (buffer pH 2.5:methanol, 34:66 v/v) at 1.5 mL·min −1 and 274 nm detection. Linearity (1–50 µg·mL −1 , R 2 > 0.999) was demonstrated with sensitive detection limits (LOD = 0.20 µg·mL −1 [MTC], 0.25 µg·mL −1 [ETC] and LOQ = 0.60 µg·mL −1 [MTC], 0.75 µg·mL −1 [ETC]). Environmental sustainability was rigorously confirmed using eight green metrics (AGREE, ComplexGAPI, AMVI), yielding an analytical eco-scale score of 84, surpassing conventional methods in eco-friendliness . In vivo studies on complete Freund’s adjuvant-induced rheumatoid arthritis rats revealed the MTC–ETC combination’s potent anti-inflammatory and anti-arthritic effects, including reduced serum c-reactive protein levels ( p < 0.05) and preserved hepatorenal function. Validated per United States Food and Drug Administration guidelines, this method offers a fast, economical, and eco-conscious solution for pharmacokinetic studies and therapeutic monitoring, positioning the MTC–ETC combination as a promising, safe therapy for rheumatoid arthritis.