A new stability-indicating RP-HPLC method was developed for the simultaneous determination of fexofenadine hydrochloride and montelukast in combined dosage form, using a Aligent, Zorbax (Make: 150 mmx4.6 mm I.D; particle size 5μm and a mobile phase composed of phospahte buffer (pH 4.0): Acetonitile (60:40 v/v) at a flow rate of 1.0mL/min. The retention times of fexofenadine hydrochloride and montelukast were found to be 10.16 and 12.03 min, respectively. Linearity was established for fexofenadine hydrochloride and montelukast in the range of 10- 30μg/ml and 5.0-15μg/ml, respectively. The percentage recoveries of fexofenadine hydrochloride and montelukast were found to be in the range of 99.80 to 99.90 and 99.50 to 99.93 respectively. Both the drugs were subjected to acid and base hydrolysis, oxidation, photolytic, and thermal degradation conditions. The degradation products of fexofenadine hydrochloride and montelukast were well resolved from the pure drug with significant differences in their retention time values. This method can be successfully employed for simultaneous quantitative analysis of montelukast and fexofenadine hydrochloride in various combined formulations.
