A Validated Stability-Indicating RP-HPLC Method for Concurrent Determination of Minoxidil and Dutasteride in a Synthetic Mixture
Abstract
The combined use of minoxidil and dutasteride has gained increasing attention in the management of androgenetic alopecia, making the availability of a reliable analytical method essential for quality control and formulation studies. Existing methods are limited by lengthy run times, lack of selectivity, or absence of simultaneous estimation. To address this gap, a novel, simple, selective, and rapid Reversed-Phase High-Performance Liquid Chromatographic (RP-HPLC) method was developed and validated for the simultaneous estimation of minoxidil and dutasteride in a synthetic mixture. Chromatographic separation was achieved using an Inertsil ODS column (100 mm × 4.6 mm, 3 μm) with a mobile phase of 0.1% triethylamine: acetonitrile (35:65, v/v) at a flow rate of 1.0 mL/min. Detection was performed at 240 nm with the column maintained at 25°C. The developed RP-HPLC method successfully resolved minoxidil and dutasteride, with retention times of 1.7 min and 6.7 min, respectively. Method validation demonstrated excellent linearity over the concentration ranges of 250–750 μg/mL for minoxidil and 2.50–7.50 μg/mL for dutasteride. The method also showed high accuracy, with recovery values ranging from 99.6% to 101.0% for minoxidil and 98.7% to 101.1% for dutasteride. The clear separation between minoxidil (1.7 minutes) and dutasteride (6.7 minutes) enabled simultaneous, interference-free quantification of both analytes. The retention of degradation peaks away from the analyte peaks under all five stress conditions confirmed the method's stability-indicating capability, supporting its suitability for shelf-life and quality control testing. The wide difference in linearity ranges reflects the large disparity in dose strength between the two drugs, while recovery values within 98–102% indicate high accuracy per ICH Q2(R1) criteria. The developed method offers significant advantages in terms of speed, sensitivity, and reliability, making it highly suitable for routine quality control, stability testing, and pharmaceutical analysis of minoxidil–dutasteride in a synthetic mixture.