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Clotrimazole and Betamethasone (Clotrimazole / Betamethasone Dipropionate Topical) - Description and Clinical Pharmacology

 
 



Rx Only

FOR TOPICAL USE ONLY. NOT FOR OPHTHALMIC, ORAL, OR INTRAVAGINAL USE.
NOT RECOMMENDED FOR PATIENTS UNDER THE AGE OF 17 YEARS AND NOT RECOMMENDED FOR DIAPER DERMATITIS.

DESCRIPTION:

Clotrimazole and betamethasone dipropionate lotion USP, contains combinations of clotrimazole USP, a synthetic antifungal agent, and betamethasone dipropionate USP, a synthetic corticosteroid, for dermatologic use.

Chemically, clotrimazole is 1-(o-chloro-α,α-diphenylbenzyl)imidazole, with the empirical formula C22H17CIN2, a molecular weight of 344.84, and the following structural formula:

Clotrimazole is an odorless, white crystalline powder, insoluble in water and soluble in ethanol.

Betamethasone dipropionate has the chemical name 9-fluoro-11β,17,21-trihydroxy-16β-methylpregna-1,4-diene-3,20-dione 17,21-dipropionate, with the empirical formula C28H37FO7, a molecular weight of 504.59, and the following structural formula:

Betamethasone dipropionate is a white to creamy white, odorless crystalline powder, insoluble in water.

Each gram of clotrimazole and betamethasone dipropionate lotion USP contains 10 mg clotrimazole and 0.64 mg betamethasone dipropionate (equivalent to 0.5 mg betamethasone), in a hydrophilic base of purified water, mineral oil, white petrolatum, cetostearyl alcohol, ceteareth-30, propylene glycol, sodium phosphate monobasic monohydrate, and phosphoric acid (used for pH adjustment, if required); benzyl alcohol as a preservative. Clotrimazole and betamethasone dipropionate lotion USP is opaque and white in color.

CLINICAL PHARMACOLOGY

Clotrimazole and Betamethasone Dipropionate

No comparative studies have been conducted with clotrimazole and betamethasone dipropionate lotion and clotrimazole alone. Use of corticosteroids in the treatment of a fungal infection may lead to suppression of host inflammation leading to worsening or decreased cure rate.

Clotrimazole

Skin penetration and systemic absorption of clotrimazole following topical application of clotrimazole and betamethasone dipropionate lotion have not been studied. The following information was obtained using 1% clotrimazole cream and solution formulations. Six hours after the application of radioactive clotrimazole 1% cream and 1% solution onto intact and acutely inflamed skin, the concentration of clotrimazole varied from 100 mcg/cm3 in the stratum corneum, to 0.5 to 1 mcg/cm3 in the reticular dermis, and 0.1 mcg/cm3 in the subcutis. No measurable amount of radioactivity (<0.001 mcg/mL) was found in the serum within 48 hours after application under occlusive dressing of 0.5 mL of the solution. Only 0.5% or less of the applied radioactivity was excreted in the urine.

Microbiology

Mechanism of Action: Clotrimazole is an imidazole antifungal agent. Imidazoles inhibit 14-α-demethylation of lanosterol in fungi by binding to one of the cytochrome P-450 enzymes. This leads to the accumulation of 14-α-methylsterols and reduced concentrations of ergosterol, a sterol essential for a normal fungal cytoplasmic membrane. The methylsterols may affect the electron transport system, thereby inhibiting growth of fungi.

Activity In Vivo: Clotrimazole has been shown to be active against most strains of the following dermatophytes, both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section: Epidermophyton floccosum, Trichophyton mentagrophytes, and Trichophyton rubrum.

Activity In Vitro: In vitro, clotrimazole has been shown to have activity against many dermatophytes, but the clinical significance of this information is unknown.

Drug Resistance: Strains of dermatophytes having a natural resistance to clotrimazole have not been reported.

Resistance to azoles including clotrimazole has been reported in some Candida species. No single-step or multiple-step resistance to clotrimazole has developed during successive passages of Trichophyton mentagrophytes.

Betamethasone Dipropionate

Betamethasone dipropionate, a corticosteroid, has been shown to have topical (dermatologic) and systemic pharmacologic and metabolic effects characteristic of this class of drugs.

Pharmacokinetics: The extent of percutaneous absorption of topical corticosteroids is determined by many factors, including the vehicle, the integrity of the epidermal barrier and the use of occlusive dressings. (See DOSAGE AND ADMINISTRATION section). Topical corticosteroids can be absorbed from normal intact skin. Inflammation and/or other disease processes in the skin may increase percutaneous absorption of topical corticosteroids. Occlusive dressings substantially increase the percutaneous absorption of topical corticosteroids. (See DOSAGE AND ADMINISTRATION section).

Once absorbed through the skin, the pharmacokinetics of topical corticosteroids are similar to systemically administered corticosteroids. Corticosteroids are bound to plasma proteins in varying degrees. Corticosteroids are metabolized primarily in the liver and are then excreted by the kidneys. Some of the topical corticosteroids and their metabolites are also excreted into the bile.

Studies performed with clotrimazole and betamethasone dipropionate lotion indicate that this topical combination anti-fungal/corticosteroids may have vasoconstrictor potencies in a range that is comparable to high potency topical corticosteroids. Therefore use is not recommended in patients less than 17 years of age, in diaper dermatitis, and under occlusion.

CLINICAL STUDIES (Clotrimazole and Betamethasone Dipropionate Lotion)

In the treatment of tinea pedis twice daily for 4 weeks, clotrimazole and betamethasone dipropionate lotion was shown to be superior to vehicle in relieving symptoms of erythema, scaling, pruritus, and maceration at week 2.

Clotrimazole and betamethasone dipropionate lotion was also shown to have a superior mycological cure rate compared to vehicle 2 weeks after discontinuation of treatment. It is unclear if the relief of symptoms at 2 weeks in this clinical study with clotrimazole and betamethasone dipropionate lotion was due to the contribution of betamethasone dipropionate, clotrimazole, or both.

In the treatment of tinea cruris twice daily for 2 weeks, clotrimazole and betamethasone dipropionate lotion was shown to be superior to vehicle in the relief of symptoms of erythema, scaling, pruritus after 3 days. It is unclear if the relief of symptoms after 3 days in this clinical study with clotrimazole and betamethasone dipropionate lotion was due to the contribution of betamethasone dipropionate, clotrimazole, or both.

The comparative efficacy and safety of clotrimazole and betamethasone dipropionate lotion versus clotrimazole alone in a lotion vehicle have not been studied in the treatment of tinea pedis or tinea cruris or tinea corporis. The comparative efficacy and safety of clotrimazole and betamethasone dipropionate lotion and clotrimazole and betamethasone dipropionate cream have also not been studied.

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