Objective: A simple, reliable, and rapid RP-HPLC method showing stability has been established to detect Doxepin Hydrochloride (DOX) with its degraded products. The proposed method has been validated for specificity, linearity, system suitability, accuracy, precision, robustness, LOD, and LOQ as per ICH guidelines. All parameters were found to be within the accepted limits, affirming the method's reliability.

Methods: Analysis was conducted using RP-HPLC on a Phenomenex C18 Luna column (250 mm × 4.6 mm id, 5 µm) with a mobile phase comprising methanol, acetonitrile, and buffer (40:30:30, v/v/v) and a flow rate of 0.5 ml/min. The detection was performed with a UV detector set at 254 nm. Diverse methods have been employed to investigate forced degradation studies, including acid-base hydrolysis, photolysis, thermal degradation, and oxidation. These studies were conducted both in bulk and in capsule formulations of DOX.

Results: The retention time (tR) of DOX was 2.92 minutes, and all parameters met acceptable limit values. The response exhibited linearity over a concentration range of 10 to 50 µg/ml (R2 = 0.9974). The percentage of DOX recovered from the pharmaceutical cream dosage form ranged from 97.67% to 101%. Sensitivity levels for the developed method were indicated by limit of detection (LOD) and limit of quantification (LOQ) values of 0.40–0.50 µg/ml. The proposed method was validated according to ICH guidelines.

Conclusion: Hence, a simple, reliable, accurate, and precise HPLC method was developed, proving suitable for the analysis of DOX in both bulk and commercial formulations.