Topical drug classification

A variety of prescription and over-the-counter topical products currently marketed as lotions, gels, creams, and ointments are evaluated using different techniques including rheology (viscosity and shear rate versus shear stress), loss on drying (LOD), specific gravity, surface tension, thermogravimetric analysis (TGA), water absorption, dilution properties, microscopic evaluation, transmittance of visible light, appearance and composition. Rheology is the most discriminating property separating creams and lotions. Water plus volatiles (as measured by LOD) and composition separate ointments and creams. Composition and thermal behavior separate gels from the other dosage forms. Based on these findings, new definitions and a decision tree are presented to assist in the determination of the appropriate nomenclature for a topical dosage form.