Pharmacokinetics

The penetration of oxiconazole nitrate into different layers of the skin was assessed using an in vitro permeation technique with human skin. Five hours after application of 2.5 mg/cm2 of oxiconazole nitrate cream onto human skin, the concentration of oxiconazole nitrate was demonstrated to be 16.2 μmol in the epidermis, 3.64 μmol in the upper corium, and 1.29 μmol in the deeper corium. Systemic absorption of oxiconazole nitrate is low. Using radiolabeled drug, less than 0.3% of the applied dose of oxiconazole nitrate was recovered in the urine of volunteer subjects up to 5 days after application of the cream formulation.

Neither in vitro nor in vivo studies have been conducted to establish relative activity between the lotion and cream formulations.

Microbiology

Oxiconazole nitrate is an imidazole derivative whose antifungal activity is derived primarily from the inhibition of ergosterol biosynthesis, which is critical for cellular membrane integrity. It has in vitro activity against a wide range of pathogenic fungi.

Oxiconazole has been shown to be active against most strains of the following organisms both in vitro and in clinical infections at indicated body sites (see INDICATIONS AND USAGE):

  Epidermophyton floccosum
  Trichophyton mentagrophytes
  Trichophyton rubrum
  Malassezia furfur

The following in vitro data are available; however, their clinical significance is unknown. Oxiconazole exhibits satisfactory in vitro minimum inhibitory concentrations (MICs) against most strains of the following organisms; however, the safety and efficacy of oxiconazole in treating clinical infections due to these organisms have not been established in adequate and well-controlled clinical trials:

  Candida albicans
  Microsporum audouini
  Microsporum canis
  Microsporum gypseum
  Trichophyton tonsurans
  Trichophyton violaceum

General

OXISTAT Lotion is for external dermal use only. Avoid introduction of OXISTAT Lotion into the mouth, eyes, or vagina. If a reaction suggesting sensitivity or chemical irritation should occur with the use of OXISTAT Lotion, treatment should be discontinued and appropriate therapy instituted. If signs of epidermal irritation should occur, the drug should be discontinued.

Information for Patients

The patient should be instructed to:

1.

Use OXISTAT as directed by the physician. The hands should be washed after applying the medication to the affected area(s). Avoid contact with the eyes, nose, mouth, and other mucous membranes. OXISTAT is for external use only.

2.

Use the medication for the full treatment time recommended by the physician, even though symptoms may have improved. Notify the physician if there is no improvement after 2 to 4 weeks, or sooner if the condition worsens (see below).

3.

Inform the physician if the area of application shows signs of increased irritation, itching, burning, blistering, swelling, or oozing.

4.

Avoid the use of occlusive dressings unless otherwise directed by the physician.

5.

Do not use this medication for any disorder other than that for which it was prescribed.

Drug Interactions

Potential drug interactions between OXISTAT and other drugs have not been systematically evaluated.

Carcinogenesis, Mutagenesis, Impairment of Fertility

Although no long-term studies in animals have been performed to evaluate carcinogenic potential, no evidence of mutagenic effect was found in 2 mutation assays (Ames test and Chinese hamster V79 in vitro cell mutation assay) or in 2 cytogenetic assays (human peripheral blood lymphocyte in vitro chromosome aberration assay and in vivo micronucleus assay in mice).

Reproductive studies revealed no impairment of fertility in rats at oral doses of 3 mg/kg/day in females (1 time the human dose based on mg/m2) and 15 mg/kg/day in males (4 times the human dose based on mg/m2). However, at doses above this level, the following effects were observed: a reduction in the fertility parameters of males and females, a reduction in the number of sperm in vaginal smears, extended estrous cycle, and a decrease in mating frequency.

Pregnancy

Teratogenic Effects

Reproduction studies have been performed in rabbits, rats, and mice at oral doses up to 100, 150, and 200 mg/kg/day (57, 40, and 27 times the human dose based on mg/m2), respectively, and revealed no evidence of harm to the fetus due to oxiconazole nitrate. There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.

Nursing Mothers

Because oxiconazole is excreted in human milk, caution should be exercised when the drug is administered to a nursing woman.

Pediatric Use

Safety and effectiveness in pediatric patients have not been established.

Geriatric Use

A limited number of patients at or above 60 years of age (n ~ 396) have been treated with oxiconazole nitrate cream in US and non-US clinical trials, and a limited number (n = 43) have been treated with OXISTAT Lotion in US clinical trials. The number of patients is too small to permit separate analysis of efficacy and safety. No adverse events were reported with OXISTAT Lotion in geriatric patients, and the adverse reactions reported with oxiconazole nitrate cream in this population were similar to those reported by younger patients. Based on available data, no adjustment of dosage of OXISTAT Lotion in geriatric patients is warranted.

Definitions

1.

Mycological Cure: No evidence (culture and KOH preparation) of the baseline (original) pathogen in a specimen from the affected area taken at the 2-week post-treatment visit (for tinea [pityriasis] versicolor, mycological cure was limited to KOH only).

2.

Treatment Success: Both a global evaluation of 90% clinical improvement and a microbiologic eradication (see above) at the 2-week post-treatment visit.

Tinea Pedis

The clinical trial for the lotion formulation line extension involved 332 evaluable patients with clinically and microbiologically established tinea pedis. Of these evaluable patients, 64% were diagnosed with hyperkeratotic plantar tinea pedis and 28% with interdigital tinea pedis. Seventy-seven percent (77%) had disease secondary to infection with Trichophyton rubrum, 18% had disease secondary to infection with Trichophyton mentagrophytes, and 4% had disease secondary to infection with Epidermophyton floccosum.

The results of this clinical trial at the 2-week post-treatment follow-up visit are shown in the following table:

In this study, the improvement and cure rates of the b.i.d.- and q.d.-treated groups did not differ significantly (95% confidence interval) from each other but were statistically (95% confidence interval) superior to the vehicle-treated group.