Development and validation of a sustainable stability-indicating RP-HPLC method for the quantitative determination of tenoxicam in rectal suppositories: Applications to dissolution testing, content uniformity, and proposed degradation pathways

A rapid, sensitive, and environmentally sustainable RP-HPLC method was developed and validated for the determination of tenoxicam (TEN) in bulk drug and a newly registered dosage form, rectal suppositories. The same chromatographic conditions were successfully applied to assay, content uniformity, and dissolution testing. Separation was achieved on a Hypersil BDS C18 column (150 × 4.6 mm, 5 μm) using an isocratic mobile phase of 0.025 M potassium phosphate buffer (the potassium phosphate buffer was prepared by dissolving 3.4 g of potassium dihydrogen phosphate in 1 L of bi-distilled water pH 3.5 adjusted with concentrated orthophosphoric acid 85% (w/v)) and ethanol (60:40, v/v) at 1.0 mL/min, with PDA detection at 375 nm and an analysis time of 3.731 min ± 0.132. The method exhibited excellent linearity over 0.55–33.00 μg/mL (R 2 = 0.9999), with detection and quantification limits of 0.02 and 0.06 μg/mL, respectively. Recoveries ranged from 99.80% to 100.94%, with precision RSD values below 2.0%. The method was robust to small variations in flow rate, column type, and detection wavelength. Forced-degradation studies showed degradation of 7.00%, 3.48%, 8.31%, 2.94%, and 0.29% under acidic, alkaline, oxidative, thermal, and photolytic conditions, respectively, with satisfactory separation of degradation products from TEN. Favorable sustainability was demonstrated by AGREE, AGSA, BAGI, CaFRI, AES, MoGAPI, SAMI, AGREEprep, AGSA-prep, and TriCA scores of 0.61, 69.44, 72.50, 91.00, 88.00, 78.00, 38.00, 0.63, 71.00%, and 75.00%, respectively. The proposed method is suitable for routine quality control, content uniformity, dissolution, and stability assessment of TEN rectal suppositories.