1Assistant Professor of Pharmaceutics, Pharmacy School
2Associate Professor of Dermatology, Kerman University of Medical Sciences and Health Services, Kerman, Iran
Acne vulgaris is a chronic and prevalent usually self-limited disorder. Topical medication is the main route for acne therapy. In this disorder the most widely used topical preparations are antibiotics such as Erythromycin and keratolytic agents such as Tretinoin. Excellent results with minimal side effects may be achieved by a fixed combination of Tretinoin and Erythromycin. This combination therapy increases efficacy and a faster response in the treatment of acne may be achieved. The purpose of this work was to assess a suitable formulation of Erytromycin and Tretinoin in a topical gel base. UV spectrophotometer analysis was chosen for Erythromycin and Tretinoin assay. This method was adapted to assay Erytromycin and Tretinoin in their combination. The proposed method for Erythromycin was the formation of a complex with Onitrobenzaldehyde, in glacial acetic acid and in the presence of hydrochloric acid, which manifested maximum absorbance at 486nm. For the measurement of Tretinoin, the absorption peak at 355nm in acidic Ethanol-Water-Iso Propyl alcohol (IPA) mixture was suitable. In order to formulate the Tretinoin and Erythromycin in a gel base, gelling agents, plasticizers, solvents, cosolvents such as Carbopol, HPC, HPMC, Ethanol, Propylene Glycol (PG), Isopropyl Alcohol (IPA) and Water have been used. By using tertiary diagrams, the most proportionate percentage of gel constituents have been determined. The formulations have been controlled for rheological, organoleptic properties and physical and chemical stability under several conditions (4, 25, 40°C). The release of drugs from the gels was studied using Franz diffusion cell and the best formulations were chosen. Drug release rates followed Higuchi's law. The results indicated that Erythromycin and Tretinoin could be formulated in a gel base with a suitable release profile and presented to pharmaceutical market.