Like other topical corticosteroids, clobetasol propionate has anti-inflammatory, antipruritic, and vasoconstrictive properties. The mechanism of the anti-inflammatory activity of the topical steroids, in general, is unclear. 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 A2.
The effect of CLOBEX® Spray, % on hypothalamic-pituitary-adrenal (HPA) axis function was investigated in adults in two studies. In the first study, patients with plaque psoriasis covering at least 20% of there body applied CLOBEX® Spray, % twice daily for up to 4 weeks. 15% (2 out of 13) of patients displayed adrenal suppression after 4 weeks of use based on the Cosyntropin Stimulation Test. The laboratory suppression was transient; all subjects returned to normal after cessation of drug use. In the second study, patients with plaque psoriasis covering at least 20% of their body applied CLOBEX® Spray, % twice daily for either 2 or 4 weeks. 19% (4 out of 21) of patients treated for 2 weeks and 20% (3 out of 15) of patients treated for 4 weeks displayed adrenal suppression at the end of treatment based on the Cosyntropin Stimulation Test. The laboratory suppression was transient; all subjects returned to normal after cessation of drug use. In these studies, HPA axis suppression was defined as serum cortisol level ≤ 18 μg/dL 30-min post cosyntropin (ACTH 1-24) stimulation [see WARNINGS AND PRECAUTIONS ].