Emollients in dermatological creams: Early evaluation for tailoring formulation and therapeutic performance

The targeted choice of the emollient of a cream determines its physicochemical properties and clinical effectiveness. This work researched the effects of emollient properties on the final characteristics and potential performance of oil-in-water dermatological creams. Seven emollients with different chemical characteristics and structures (alkane, triglyceride, ether, silicone, vegetable oils, and mineral oil) were tested in a model formulation. Early stability, pH, droplet size distribution, rheology, tackiness, adhesivity, spreadability, tribology, and release profile of a lipophilic substance model (in Franz cells, through a synthetic membrane, for six hours) were assessed. The creams had acid epicutaneous pH and a "shear-thinning" "solid-like" viscoelastic behavior. Among the seven emollients' properties, polarity, density, and viscosity were the most influential. Droplet parameters were the most impacted, pH and release were moderately affected, and the textural properties were lowly to moderately impacted. The emollient substitution in the model formulation affected the experimental parameters differently, allowing formulation optimization and tailoring its potential therapeutic performance regarding drug release, coadjutant effects, and dwell time on the skin. By looking at the creams' characteristics, it was possible to select the best-suited emollients for releasing a lipophilic drug, applying on painful skin, and formulation in wash-off products or leave-on protective barrier creams.