Method of finasteride gel preparation
Since the water solubility of Finesteride gel is very low, thus, at the beginning of work, solubility had to be increased. For this reason, solvent-aid was used. The solvents-aid is water mixable organic solvents, in which by decreasing solubility, and with surface tension of water, will cause increase water solubility of non-polar materials. An adequate amount of ethanol to increase solubility was determined by several examinations and by setting the drug solubility in different percentages of water-ethanol. After setting and preparing the suitable solvent to solve finasteride, several examinations to select the best polymer were done by different materials. For this reason, first the selected polymer was poured on a glass surface, containing an adequate drug solving system, and was maintained in lab temperature for 24 hours. Then, the receiving system was mixed by an electric mixer by velocity of 600 cycles per minute, until it was completely pure. The results showed that 40% water and 60% ethanol are the best solvent system, and hydroxyl propyl methyl cellulose (HPMC) is the best polymer. Preparation of this drug did not need a preservative. Physical stability of the drug as a viewpoint of deposition or opacity in 4°C in refrigerator was evaluated. Since the time frame between drug production and consumption was about one week, there was no need for chemical assessment. In addition, the placebo gel without drug was prepared by the same system. Because, finasteride 1% has the most dermal absorption, therefore, in this study finasteride gel 1% was prepared and used.