Green stability-indicating RP-HPLC method for simultaneous bioanalysis of tedizolid phosphate and ciprofloxacin in human plasma.

Tedizolid phosphate (TP) and ciprofloxacin (CIP) represent orally effective antibiotics that are often administered in combination for hospitalized patients with complicated or mixed infections, aiming to provide wide antimicrobial coverage. This study describes, for the first time, the establishment of an environmentally sustainable reversed-phase HPLC approach for the simultaneous bioanalysis of TP and CIP in human plasma. The developed chromatographic method allowed for rapid separation within 4 min employing a methanol-water mobile phase, thereby reducing solvent consumption and improving environmental sustainability. The method was validated according to the validation parameters investigated in the present study, with reference to the US FDA Bioanalytical Method Validation Guidance. Excellent linearity was achieved over concentration ranges of 5-90 µg/mL (TP) and 5-80 µg/mL (CIP) in pure samples, and 0.5-30 µg/mL (TP) and 0.5-10 µg/mL (CIP) in human plasma. LOD/LOQ values were 1.60/4.86 µg/mL for TP and 1.58/4.78 µg/mL for CIP in pure samples, and 0.16/0.49 µg/mL for TP and 0.10/0.31 µg/mL for CIP in spiked human plasma. The proposed method was characterized by adequate sensitivity and demonstrated strong performance in terms of accuracy, precision, specificity, and robustness. Furthermore, it proved effective in assessing the forced degradation of TP and CIP under diverse stress conditions, confirming its capability as a stability-indicating approach. The environmental impact of the method was comprehensively evaluated using multiple established greenness and blueness assessment tools, confirming its favorable environmental profile. Overall, the developed approach presents a rapid, highly accurate, and environmentally sustainable strategy for the simultaneous bioanalysis of TP and CIP in bulk drugs, pharmaceutical formulations, and human plasma.