On topical application of a semisolid drug, the drug diffuses passively out of its vehicle and partitions into either the stratum corneum or the sebum-filled ducts of the pilosebaceous glands. Inward diffusive movements continue from these locations to the viable epidermal and dermal points of entry. Thus, a concentration gradient develops across the skin up…

Learning Objectives Semisolid dosage forms are mainly meant for external application on the skin or mucous membrane. They are traditionally used for treating topical ailments. They are also used for treating ophthalmic, nasal, buccal, rectal and vaginal ailments. Semisolid dosage forms may be used for therapeutic, cosmetic or protective properties. Examples are ointments, pastes, creams,…