DefinePK

Abstract

A simple, precise, accurate, and robust reverse-phase high-performance liquid chromatography (RP-HPLC) method was developed and validated for the simultaneous estimation of Doxofylline and Montelukast in combined pharmaceutical dosage forms. The primary objective was to establish a stability-indicating method capable of separating the active pharmaceutical ingredients from their degradation products under various stress conditions. Chromatographic separation was achieved using a Discovery C18 column (250mm × 4.6 mm, 5 μm) with a mobile phase of acetonitrile and 0.01 potassium dihydrogen phosphate (50:50, v/v) at a flow rate of 1.0 mL/min, and detection at 240 nm. The methodwas validated as per ICH Q2(R1) guidelines and demonstrated excellent linearity (R² =0.999) in the concentration ranges of 40–240 µg/mL for Doxofylline and 1–6 µg/mL forMontelukast. The LOD and LOQ were found to be 1.26 and 3.81 µg/mL for Doxofylline and 0.01 and 0.02 µg/mL for Montelukast, respectively. Precision, accuracy, and robustness studies confirmed the method’s reliability. Forced degradation studies under acid, alkali,oxidative, thermal, photolytic, and neutral conditions showed no interference at the analyteretention times, confirming the method’s stability-indicating capability. The validated method is suitable for routine quality control and stability testing of combined Doxofylline and Montelukast formulations in the pharmaceutical industry.