High performance liquid chromatography (HPLC) analysis of both the drugs i.e. Minoxidil and Tretinoin was carried out in methanol and phosphate buffer pH 7.4 using Agilent HPLC system. A stock solution of 100µg/ml for both the drugs was prepared in methanol and phosphate buffer pH 7.4 and from this stock solution different dilutions were prepared to plot a calibration curve between area and concentration. The different parameters for HPLC analysis of both the drugs are indicated in Table 1.