Halcinonide is one of the available highly potent topical cor¬ticosteroids. It is a derivative of hydrocortisone and contains important modifications in its structure that alter its absorption, potency, and adverse effects compared with hydrocortisone. Halcinonide—along with desoximetasone, betamethasone, fluocinonide, and diflorasone diacetate—is classified as a Class II potency corticosteroid. Although similar in strength, halcinonide in Halog (the only topical product available that contains halcinonide) differs from many other compounds of this class in the formulation. Halcinonide cream is formulated in a biphasic base that allows for immediate-release of halcinonide upon application to the skin, followed by a delayed and sustained release of halcinonide over time. This “dual formulation” strategy allows for prolonged halcinonide activity. The formulation of halcinonide cream contains microcrystals of halcinonide. An equilibrium is established between dissolved halcinonide in the cream and non-dissolved halcinonide in the microcrystals. As soluble hal¬cinonide enters the skin, additional quantities of halcinonide from the microcrystals become available as a new equilibrium is established. This dynamic equilibrium serves to maintain a sustained level of halcinonide well beyond the time of application.