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Mentax

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Mentax

CLINICAL PHARMACOLOGY

Pharmacokinetics

In one study conducted in healthy subjects for 14 days, 6 grams of Mentax® (butenafine) Cream, 1%, was applied once daily to the dorsal skin (3,000 cm2) of 7 subjects, and 20 grams of the cream was applied once daily to the arms, trunk and groin areas (10,000 cm2) of another 12 subjects. After 14 days of topical applications, the 6-gram dose group yielded a mean peak plasma butenafine HCl concentration, Cmax, of 1.4 ± 0.8 ng/mL, occurring at a mean time to the peak plasma concentration, Tmax, of 15 ± 8 hours, and a mean area under the plasma concentration-time curve, AUC0-24 hrs of 23.9 ± 11.3 ng-hr/mL. For the 20-gram dose group, the mean Cmax was 5.0 ± 2.0 ng/mL, occurring at a mean Tmax of 6 ± 6 hours, and the mean AUC0-24 hrs was 87.8 ± 45.3 ng-hr/mL. A biphasic decline of plasma butenafine HCl concentrations was observed with the half-lives estimated to be 35 hours and > 150 hours, respectively.

At 72 hours after the last dose application, the mean plasma concentrations decreased to 0.3 ± 0.2 ng/mL for the 6-gram dose group and 1.1 ± 0.9 ng/mL for the 20-gram dose group. Low levels of butenafine HCl remained in the plasma 7 days after the last dose application (mean: 0.1 ± 0.2 ng/mL for the 6-gram dose group, and 0.7 ± 0.5 ng/mL for the 20-gram dose group). The total amount (or % dose) of butenafine HCl absorbed through the skin into the systemic circulation has not been quantitated. It was determined that the primary metabolite in urine was formed through hydroxylation at the terminal t-butyl side-chain.

In 11 patients with tinea pedis, Mentax® (butenafine) Cream, 1%, was applied by the patients to cover the affected and immediately surrounding skin area once daily for 4 weeks and a single blood sample was collected between 10 and 20 hours following dosing at 1, 2 and 4 weeks after treatment. The plasma butenafine HCl concentration ranged from undetectable to 0.3 ng/mL.

In 24 patients with tinea cruris, Mentax® (butenafine) Cream, 1%, was applied by the patients to cover the affected and immediately surrounding skin area once daily for 2 weeks (mean average daily dose: 1.3 ± 0.2 g). A single blood sample was collected between 0.5 and 65 hours after the last dose, and the plasma butenafine HCl concentration ranged from undetectable to 2.52 ng/mL (mean ± SD: 0.91 ± 0.15 ng/mL). Four weeks after cessation of treatment, the plasma butenafine HCl concentration ranged from undetectable to 0.28 ng/mL.

Microbiology

Butenafine HCl is a benzylamine derivative with a mode of action similar to that of the allylamine class of antifungal drugs. Butenafine HCl is hypothesized to act by inhibiting the epoxidation of squalene, thus blocking the biosynthesis of ergosterol, an essential component of fungal cell membranes. The benzylamine derivatives, like the allylamines, act an earlier step in the ergosterol biosynthesis pathway than the azole class of antifungal drugs. Depending on the concentration of the drug and the fungal species tested, butenafine HCl may be fungicidal or fungistatic in vitro. However, the clinical significance of these in vitro data is unknown.

Butenafine HCl has been shown to be active against most strains of the following microorganisms, both in vitro and in clinical infections as described in the INDICATIONS section:

Epidermophyton floccosum
Malassezia furfur

Trichophyton mentagrophytes

Trichophyton rubrum

Trichophyton tonsurans

Clinical Studies

Interdigital Tinea Pedis

Once Daily Four Week Dosing

In the following data presentations, patients with interdigital tinea pedis in the absence of moccasin-type tinea pedis and onychomycosis were studied. The term “Mycological Cure” is defined as both negative KOH and culture. The term “Effective Treatment” refers to patients who had a “Mycological Cure” and an Investigator's Global of either “Excellent” (80% to 99% improvement) or “Cleared” (100% improvement). The term “Overall Cure” refers to patients who had both a “Mycological Cure” and an Investigator's Global Assessment of “Cleared”(100% improvement).

Data from the two controlled studies in which Mentax® (butenafine) Cream, 1%, was used once daily for 4 weeks have been combined in the table below. Patients were treated for 4 weeks and evaluated 4 weeks post-treatment. In the “per protocol” analysis shown in the table below, statistical significance (Mentax® (butenafine) vs. vehicle) was assessed 4 weeks post-treatment.

Interdigital Tinea Pedis: 4-Week Dosing Regimen

Patient Outcome Category WEEK 4
(End of Treatment)
WEEK 8
(4 Weeks Post-Treatment)
Butenafine Vehicle Butenafine Vehicle
Mycological Cure 89%
(83/93)
57%
(51/90)
90%
(66/73)
38%
(25/66)
Effective Treatment 57%
(53/93)
28%
(25/90)
74%
(54/73)
26%
(17/66)
Overall Cure 15%
(14/93)
8%
(7/90)
25%
(18/73)
9%
( 6/66)

Twice-Daily One Week Dosing

In the following data presentations, patients with interdigital tinea pedis in the absence of moccasin-type tinea pedis were studied. Patients with concurrent onychomycosis were not excluded. The term “Mycological Cure” is defined as both negative KOH and culture. The term “Effective Treatment” refers to patients who had a “Mycological Cure” and an Investigator's Global of either “Excellent” (90% to 99% improvement) or “Cleared” (100% improvement). The term “Overall Cure” refers to patients who had both a “Mycological Cure” and an Investigator's Global Assessment of “Cleared” (100% improvement).

Data from the two controlled studies in which Mentax® (butenafine) Cream, 1%, was used twice daily for 1 week have been combined in the table below. Patients were treated for 1 week and evaluated 5 weeks post-treatment. In the “modified-intent-to-treat” analysis shown in the table below, statistical significance (Mentax® (butenafine) vs. vehicle) was assessed 5 weeks post-treatment.

Interdigital Tinea Pedis: 1-Week Dosing Regimen

Patient Outcome Category WEEK 1
(End of Treatment)
WEEK 6
(5 Weeks Post-Treatment)
Butenafine Vehicle Butenafine Vehicle
Mycological Cure 44%
(111/253)
28%
(75/265)
79%
(200/253)
20%
(54/265)
Effective Treatment 5%
(12/253)
3%
(7/265)
38%
(95/253)
7%
(18/265)
Overall Cure 0.4%
(1/253)
0.4%
(1/265)
*15%
(37/253)
0.7%
(2/265)
* The Overall Cure Rate of 15% is calculated from a 9% rate in one trial and a 20% rate in the second trial.

Tinea Corporis and Tinea Cruris

In the following data presentations, patients with tinea corporis or tinea cruris were studied. The term “Mycological Cure” is defined as both negative KOH and culture. The term “Effective Treatment” refers to patients who had a “Mycological Cure” and an Investigator's Global of either “Excellent” (90% to 99% improvement) or “Cleared” (100% improvement). The term “Overall Cure” refers to patients who had both a “Mycological Cure” and an Investigator's Global Assessment of “Cleared”(100% improvement).

Separate studies compared Mentax® (butenafine) Cream to vehicle applied once daily for 2 weeks in the treatment of tinea corporis and tinea cruris. Patients were treated for 2 weeks and evaluated 4 weeks post-treatment. All subjects with a positive baseline exam (including positive culture and KOH) and who were dispensed medication were included in the “modified intent-to-treat” analysis shown in the table below. Statistical significance (Mentax® (butenafine) vs. vehicle) was achieved for all patient outcome categories at Week 2 (end of treatment) and Week 6 (4 weeks post-treatment).

Tinea Corporis

Patient Outcome Category WEEK 2
(End of Treatment)
WEEK 6
(4 Weeks Post-Treatment)
Butenafine Vehicle Butenafine Vehicle
Mycological Cure 88%
(37/42)
28%
(10/36)
88%
(37/42)
17%
(6/36)
Effective Treatment 60%
(25/42)
17%
(6/36)
81%
(34/42)
14%
(5/36)
Overall Cure 31%
(13/42)
3%
(1/36)
67%
(28/42)
14%
(5/36)

Tinea Cruris

Patient Outcome Category WEEK 2
(End of Treatment)
WEEK 6
(4 Weeks Post-Treatment)
Butenafine Vehicle Butenafine Vehicle
Mycological Cure 78%
(29/37)
11%
(4/38)
81%
(30/37)
13%
(5/39)
Effective Treatment 57%
(21/37)
8%
(3/39)
73%
(27/37)
5%
(2/39)
Overall cure 32%
(12/37)
8%
(3/39)
62%
(23/37)
3%
(1/39)

Tinea (pityriasis) versicolor

In the following data presentations, patients with tinea (pityriasis) versicolor were studied. The term “Negative Mycology” is defined as absence of hyphae in a KOH preparation of skin scrapings, i.e.; no fungal forms seen or the presence of yeast cells (blastospores) only. The term “Effective Treatment” is defined as Negative Mycology plus total signs and symptoms score (on a scale from zero to three) for erythema, scaling, and pruritus equal to or less than 1 at Week 8. The term “Complete Cure” refers to patients who had negative mycology plus sign/symptoms scores of zero for erythema, scaling, and pruritus.

Two separate studies compared Mentax® (butenafine) Cream to vehicle applied once daily for 2 weeks in the treatment of tinea (pityriasis) versicolor. Patients were treated for 2 weeks and were evaluated at the following weeks post-treatment: 2 (Week 4) and 6 (Week 8). All subjects with a positive baseline KOH and who were dispensed medications were included in the “intent-to-treat” analysis shown in the table below. Statistical significance (Mentax® (butenafine) vs. vehicle) was achieved for Effective Treatment, but not Complete Cure at 6 weeks post-treatment in Study 31. Marginal statistical significance (p = 0.051) (Mentax® (butenafine) vs. vehicle) was achieved for Effective Treatment but not Complete Cure at 6 weeks post-treatment in Study 32. Data from these two controlled studies are presented in the table below.

Tinea Veriscolor

Proportion (%) of responders in pivotal clinical trials (all randomized patients)
Patient Response Category Week@ Study 31 Study 32
Butenafine Vehicle Butenafine Vehicle
Complete Cure * 2 41/87 (47%) 11/40 (28%) 29/85 (34%) 12/41 (29%)
4 43/86 (50%) 15/42 (36%) 36/83 (43%) 13/41 (32%)
8 44/87 (51%) 15/42 (36%) 30/86 (35%) 10/43 (23%)
Effective Treatment** 2 56/87 (64%) 16/40 (40%) 46/85 (54%) 16/41 (39%)
4 50/86 (58%) 19/42 (45%) 45/83 (54%) 16/41 (39%)
8 48/87 (55%) 15/42 (36%) 37/86 (43%) 11/43 (26%)
Negative Mycology *** 2 57/87 (66%) 20/40 (50%) 57/85 (67%) 21/41 (51%)
4 51/86 (59%) 20/42 (48%) 52/83 (63%) 18/41 (44%)
8 48/87 (55%) 15/42 (36%) 43/86 (50%) 12/43 (28%)
@ Week 2 (end of treatment), Week 4 (2 weeks post-treatment), and Week 8 (6 weeks post-treatment)
* Negative Mycology plus absence of erythema, scaling, and pruritus
** Negative Mycology plus no or minimal involvement of erythema, scaling, or pruritus
*** Absence of hyphae in a KOH preparation of skin scrapings, i.e., no fungal forms seen or the presence of yeast cells (blastospores) only

Tinea (pityriasis) versicolor is a superficial, chronically recurring infection of the glabrous skin caused by Malassezia furfur (formerly Pityrosporum orbiculare). The commensal organism is part of the normal skin flora. In susceptible individuals the condition may give rise to hyperpigmented or hypopigmented patches on the trunk which may extend to the neck, arms and upper thighs. Treatment of the infection may not be immediately result in restoration of pigment to the affected sites. Normalization of pigment following successful therapy is variable and may take months, depending upon individual skin type and incidental sun exposure. The rate of recurrence of infection is variable.

Last reviewed on RxList: 4/3/2009
This monograph has been modified to include the generic and brand name in many instances.

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