Mechanism of Action
Like other topical corticosteroids CLOBEX® (clobetasol propionate) Spray, 0.05% 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 induction of phospholipase A2 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.
CLOBEX® Spray, 0.05% is in the super-high range of potency as demonstrated in a vasoconstrictor study in healthy subjects when compared with other topical corticosteroids. However, similar blanching scores do not necessarily imply therapeutic equivalence.
Hypothalamic-Pituitary-Adrenal (HPA) Axis Suppression
The effect of CLOBEX® Spray, 0.05% 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, 0.05% 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, 0.05% 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].
Topical corticosteroids can be absorbed from normal intact skin. Inflammation and other disease processes in the skin may increase percutaneous absorption.
There are no human data regarding the distribution of corticosteroids to body organs following topical application. Nevertheless, once absorbed through the skin, topical corticosteroids are handled through metabolic pathways similar to systemically administered corticosteroids. They are metabolized, primarily in the liver, and are then excreted by the kidneys. In addition, some corticosteroids and their metabolites are also excreted in the bile.
The efficacy of CLOBEX® Spray, 0.05% in psoriasis has been demonstrated in two randomized, vehicle controlled clinical trials, which were identical in design. The studies were conducted in patients aged 18 years and older with moderate to severe plaque psoriasis. Patients were treated twice daily for up to 4 weeks with either CLOBEX® Spray, 0.05% or vehicle spray.
Patients were evaluated on their Overall Disease Severity, a 5-point scale based on scaling, erythema, and plaque elevation that classified subjects as clear, almost clear, mild, moderate, or severe/very severe. Only patients classified as moderate or severe/very severe at baseline were enrolled in the studies. The median percent body surface area (BSA) at baseline was 6% for the two studies. The numbers of patients scored as clear or almost clear at Weeks 2 and 4 are presented in Table 2.
Table 2: Number of Patients Clear or Almost Clear on the
Overall Disease Severity Scale at Weeks 2 & 4
|Study 1||Study 2|
|Week 2||Clear||1 (2%)||0 (0%)||0 (0%)||0 (0%)|
|Almost Clear||32 (53%)||1 (2%)||28 (47%)||0 (0%)|
|Week 4||Clear||15 (25%)||0 (0%)||18 (30%)||0 (0%)|
|Almost Clear||32 (53%)||2 (3%)||31 (52%)||1 (2%)|
Last reviewed on RxList: 9/14/2012
This monograph has been modified to include the generic and brand name in many instances.
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