A Validated Stability Indicating RP-HPLC Method for Milnacipran Hydrochloride, Identification and Characterization of Forced Degradation Products Using LC-MS/MS

Abstract

A stability-indicating reverse-phase high-performance liquid chromatography (RP-HPLC) method was developed and validated for milnacipran hydrochloride. The drug was subjected to forced degradation studies under hydrolytic, oxidative, photolytic and thermal stress conditions according to International Conference on Harmonisation (ICH) guidelines. A single major degradation product (DP-1) was detected under oxidative stress conditions with 30% hydrogen peroxide at room temperature, showing 32% degradation after 4 days. The drug remained stable under acidic, basic, neutral hydrolytic, photolytic and thermal stress conditions. Chromatographic separation was achieved on a Hypersil Gold C18 column (250 mm × 4.6 mm, 5 µm) using gradient elution with 10 mM potassium dihydrogen phosphate buffer (pH 3.5) and acetonitrile as mobile phase at a flow rate of 1.0 mL/min with detection at 220 nm. The degradation product was characterized by LC-MS/MS and identified as milnacipran N-oxide. The method was validated for specificity, linearity, accuracy, precision, robustness and system suitability parameters. The validated method was successfully applied to commercial tablet formulations for stability studies.