Preparation and Evaluation of Minoxidil Gels for Topical Application in Alopecia

In the present study four minoxidil gels were prepared using carbopol, hydroxypropyl cellulose, hydroxypropyl methylcellulose and combination of hydroxypropyl cellulose, hydroxypropyl methylcellulose for the treatment of alopecia. The gels were evaluated for drug content, viscosity determination, in vitro permeation (across dialysis membrane and mouse skin), skin irritation and stability at 4, 25 and 37° tests. The drug content of the gels was found to range from 96.40±0.57 to 98.10±0.32%. The viscosity of the gels ranged between 13,780±100 and 24,950±150 cps. The drug permeation across dialysis membrane from all the formulations at the end of 24 h was almost same and ranged between 92.05±1.52 and 93.52±1.95%. Although the difference is insignificant, the percentage release of drug was found to increase in the following order of the polymer composition: HPC>Carbopol>HPMC>HPMC+HPC. All the gel formulations released almost similar amounts of drug (90.05±1.92 to 91.56±1.65%) across the mouse skin; but the cumulative amount of drug permeated across dialysis membrane was more than that of the mouse skin. The marketed topical solution was found to diffuse almost 100% of drug across dialysis membrane and mouse skin at the end of 12 h. As supported by Higuchi’s equation, the drug release mechanism from all the gels was found to be diffusion dominated. The prepared gels did not produce any dermatological reactions and were well tolerated by the mice. The gels were found to be stable with respect to viscosity, drug content and physical appearance at all temperature conditions for 3 months.