RESUMEN
Surfactants are the most common inactive ingredients used in topical drug products. Surfactants in topical products play many functional roles such as emulsifiers, permeation enhancers, and solubilizers. This study was aimed to evaluate the influence of incremental change in the concentration of a surfactant (tween 80) on the quality attributes and performance of semisolid topical products. Four creams were prepared using metronidazole as a model drug using the same manufacturing protocol and similar composition except for the concentration of tween 80, which was increased by 5% w/w across SF1 to SF4. The quality attributes like globule size, pH, drying rate, and in-vitro permeation profile were characterized. The critical quality attributes did not differ significantly across the products. However, there was a significant difference in the permeation profile of the products. The permeation flux (Jmax) varied from SF1 to SF4 (51.25 ± 35.29 to 307.98 ± 138.89 ng/cm2/h, respectively). The reason for the difference in the performance of products despite having consistent quality attributes was investigated. One of the major reasons was found to be the difference in the time course of degree of saturation of drug during the evaporative metamorphosis. This study confirms that the time course of degree of saturation is one of the important quality attributes of the topical product that could influence bioavailability and performance of topical products.