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CLINICAL PHARMACOLOGY
Like other topical
corticosteroids, halobetasol propionate has anti-inflammatory,
antipruritic
and vasoconstrictive
actions. The mechanism
of the anti-inflammatory
activity of the
topical corticosteroids,
in general, is unclear. However, corticosteroids are thought
to act by the 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.
Pharmacokinetics
The extent of percutaneous
absorption of
topical corticosteroids
is determined by many factors including the vehicle
and the integrity
of the epidermal barrier. Occlusive dressings with hydrocortisone
for up to 24 hours have not been demonstrated to increase
penetration; however, occlusion
of hydrocortisone
for 96 hours markedly enhances penetration. Topical corticosteroids
can be absorbed from normal
intact skin. Inflammation and/or other disease
processes in the skin
may increase percutaneous
absorption.
Human and animal
studies indicate that less than 6% of the applied dose
of halobetasol propionate enters the circulation
within 96 hours following topical
administration
of the cream.
Studies performed with ULTRAVATE (halobetasol propionate
cream) Cream indicate that it is in the super-high range
of potency as compared
with other topical
corticosteroids.
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