Source: FDA, National Drug Code (US) Revision Year: 2020
The most widely accepted mechanism of action of sulfonamides is the Woods-Fildes theory, based on sulfonamides acting as a competitive inhibitor of para-aminobenzoic acid (PABA) utilization, an essential component for bacterial growth. While absorption through intact skin in humans has not been determined, in vitro studies with human cadaver skin indicated a percutaneous absorption of about 4%. Sodium sulfacetamide is readily absorbed from the gastrointestinal tract when taken orally and excreted in the urine largely unchanged. The biological half-life has been reported to be between 7 to 13 hours.
The pharmacokinetics of sulfacetamide and its major metabolite sulfaniliamide in Klaron Lotion was evaluated in adult subjects (N=14) with acne vulgaris. The subjects applied Klaron Lotion to their face, back, chest, and shoulders every 12 hours for 28 days. The percentage of the applied dose of Klaron Lotion excreted in the urine as sulfacetamide plus sulfanilamide ranged from 0.08 to 0.33%.
Long-term studies in animals have not been performed to evaluate carcinogenic potential.
Animal reproduction studies have not been conducted with Klaron Lotion. It is also not known whether Klaron Lotion can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Klaron Lotion should be given to a pregnant woman only if clearly needed.
Kernicterus may occur in the newborn as a result of treatment of a pregnant woman at term with orally administered sulfonamide. There are no adequate and well-controlled studies of Klaron Lotion in pregnant women, and it is not known whether topically applied sulfonamides can cause fetal harm when administered to a pregnant woman.
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