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Extina (Ketoconazole Topical) - Description and Clinical Pharmacology

 
 



DESCRIPTION

EXTINA® Foam contains 2% ketoconazole USP, an antifungal agent, in a thermolabile hydroethanolic foam for topical application.

The chemical name for ketoconazole is piperazine, 1-acetyl-4-[4-[[2-(2,4-dichlorophenyl) -2-(1H-imidazol-l-ylmethyl)-1,3-dioxolan-4-yl]methoxy]phenyl]-, cis- with the molecular formula C26H28Cl2N4O4 and a molecular weight of 531.43. The following is the chemical structure:

EXTINA® Foam contains 20 mg ketoconazole per gram in a thermolabile hydroethanolic foam vehicle consisting of cetyl alcohol, citric acid, ethanol (denatured with tert-butyl alcohol and brucine sulfate) 58%, polysorbate 60, potassium citrate, propylene glycol, purified water, and stearyl alcohol pressurized with a hydrocarbon (propane/butane) propellant.

CLINICAL PHARMACOLOGY

Mechanism of Action

The mechanism of action of ketoconazole in the treatment of seborrheic dermatitis is not known.

Pharmacodynamics

The pharmacodynamics of EXTINA® Foam has not been established.

Pharmacokinetics

In a bioavailability study, 12 subjects with moderate to severe seborrheic dermatitis applied 3 g of EXTINA® Foam twice daily for 4 weeks. Circulating plasma levels of ketoconazole were < 6 ng/mL for a majority of subjects (75%), with a maximum level of 11 ng/mL observed in one subject.

Microbiology

Ketoconazole is an antifungal agent which inhibits the in vitro synthesis of ergosterol, a key sterol in the cell membrane of Malasseziafurfur. The clinical significance of antifungal activity in the treatment of seborrheic dermatitis is not known.

NONCLINICAL TOXICOLOGY

Carcinogenesis, Mutagenesis, Impairment of Fertility

Long-term animal studies have not been performed to evaluate the carcinogenic or photo-carcinogenic potential of EXTINA® Foam.

In oral carcinogenicity studies in mice (18-months) and rats (24-months) at dose levels of 5, 20 and 80 mg/kg/day ketoconazole was not carcinogenic. The high dose in these studies was approximately 2.4 to 4.8 times the expected topical dose in humans based on a mg/m2 comparison. In a bacterial reverse mutation assay, ketoconazole did not express any mutagenic potential. In three in vivo assays (sister chromatid exchange in humans, dominant lethal and micronucleus tests in mice), ketoconazole did not exhibit any genotoxic potential.

At oral dose levels of 75 mg/kg/day (4.5 times the expected topical human dose in mg/m2), ketoconazole impaired reproductive performance and fertility when administered to male rats (increased abnormal sperm, decreased sperm mobility and decreased pregnancy in mated females).

CLINICAL STUDIES

The safety and efficacy of EXTINA® Foam were evaluated in a randomized, double-blind, vehicle-controlled study in subjects 12 years and older with mild to severe seborrheic dermatitis. In the study, 427 subjects received EXTINA® Foam and 420 subjects received vehicle foam. Subjects applied EXTINA® Foam or vehicle foam twice daily for 4 weeks to affected areas on the face, scalp, and/or chest. The overall disease severity in terms of erythema, scaling, and induration was assessed at Baseline and week 4 on a 5-point Investigator’s Static Global Assessment (ISGA) scale.

Treatment success was defined as achieving a Week 4 (end of treatment) ISGA score of 0 (clear) or 1 (majority of lesions have individual scores for scaling, erythema, and induration that averages 1 [minimal or faint]) and at least two grades of improvement from baseline. The results are presented in Table 2. The database was not large enough to assess whether there were differences in effects in age, gender, or race subgroups.

Table 2: Efficacy Results
 

Number of Subjects

 EXTINA® Foam
N = 427
n (%)
  Vehicle Foam
N = 420
n (%)
Subjects Achieving
Treatment Success
 
239 (56%)
 
176 (42%)

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