The precise mechanism of the antiinflammatory activity of topical steroids in the treatment of steroid-responsive dermatoses, in general, is uncertain. However, corticosteroids are thought to act by the induction of phospholipase A 2 inhibitory proteins, collectively called lipocortins. It is postulated that these proteins control the biosynthesis of potent mediators of inflammation such as prostaglandins and leukotrienes by inhibiting the release of their common precursor arachidonic acid. Arachidonic acid is released from membrane phospholipids by phospholipase A 2 . Initially, however, clobetasol, like other corticosteroids, bind to the glucocorticoid receptor, which complexes, enteres the cell nucleus and modifies genetic transcription (transrepression/transactivation).
Systemic absorption of topical corticosteroids has produced reversible hypothalamic-pituitary-adrenal (HPA) suppression and/or manifestations of Cushing's syndrome in some patients. Clobetasol propionate has been shown to suppress the HPA axis at doses as low as 2 g/day. Conditions which increase systemic absorption include application of high-potency corticosteroids, use over large surface areas, prolonged use, use in areas where the epidermal barrier is disrupted (., skin abrasion), use in pediatric patients, use in patients with hepatic disease, and the use of an occlusive dressing. Clobetasol propionate preparations should not be used with occlusive dressings. Patients receiving large doses of a potent topical corticosteroid like clobetasol should be evaluated periodically for evidence of HPA axis suppression and manifestations of Cushing's syndrome. If these effects are noted, an attempt should be made to withdraw the drug, to reduce the frequency of application, or to substitute a less potent corticosteroid. Recovery of HPA axis function is generally prompt and complete upon discontinuation. Infrequently, signs and symptoms of withdrawal may occur, requiring supplemental systemic corticosteroids. It is recommended that the administration of clobetasol creams, ointments, gels, or topical solutions be limited to no more than 14 days duration, in order to limit the risk of systemic effects. Clobetasol propionate emollient creams may be administered for up to 4 weeks duration if applied to no more than 5—10% of body surface area. The total weekly dose limit of 50 g or 50 mL of a % preparation should not be exceeded for any clobetasol preparation.