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.
Pharmacodynamics
Vasoconstrictor Assay
CLOBEX® (clobetasol propionate spray) 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® (clobetasol propionate spray) 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® (clobetasol propionate spray)
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® (clobetasol propionate spray) 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].
Pharmacokinetics
The extent of percutaneous absorption of topical corticosteroids is determined
by many factors, including the vehicle, the integrity of the epidermal barrier
and occlusion.
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.
Clinical Studies
The efficacy of CLOBEX® (clobetasol propionate spray) 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® (clobetasol propionate spray) 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 |
CLOBEX®
N=60 |
Vehicle
N=60 |
CLOBEX®
N=60 |
Vehicle
N=60 |
| 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: 2/25/2011
This monograph has been modified to include the generic and brand name in many instances.