[Synthesis and antifungal activity of butenafine hydrochloride (KP-363), a new benzylamine antifungal agent]

Allylamines, Benzylamines, and Fungal Cell Permeability: A Review of Mechanistic Effects and Usefulness against Fungal Pathogens

Allylamines, naftifine and terbinafine, and the benzylamine, butenafine, are antifungal agents with activity on the fungal cell membrane. These synthetic compounds specifically inhibit squalene epoxidase, a key enzyme in fungal sterol biosynthesis. This results in a deficiency in ergosterol, a major fungal membrane sterol that regulates membrane fluidity, biogenesis, and functions, and whose damage results in increased membrane permeability and leakage of cellular components, ultimately leading to fungal cell death. With the fungal cell membrane being predominantly made up of lipids including sterols, these lipids have a vital role in the pathogenesis of fungal infections and the identification of improved therapies. This review will focus on the fungal cell membrane structure, activity of allylamines and benzylamines, and the mechanistic damage they cause to the membrane. Furthermore, pharmaceutical preparations and clinical uses of these drugs, mainly in dermatophyte infections, will be reviewed.

New Amine and Aromatic Substituted Analogues of Phencyclidine: Synthesis and Determination of Acute and Chronic Pain Activities

BACKGROUND

Phencyclidine (PCP, I) is a synthetic drug with remarkable physiological properties. PCP and its analogues exert many pharmacological activities and interact with some neurotransmitter systems in the central nervous system like particular affinity for PCP sites in NMDA receptors or dopamine uptake blocking or even both.

AIM AND OBJECTIVE

The following research, methyl group with electron-donating and dipole moment characters was added in different positions of phenyl ring along with the substitution of benzylamine (with many pharmacological effects) instead of piperidine ring of I to produce new compounds (II-V) of this family with more analgesic activities.

MATERIALS AND METHODS

Analgesic activities of these new compounds were measured by tail immersion and formalin tests for acute and chronic pains, respectively. Also, the outcomes were compared with control and PCP (10 mg/kg) groups.

RESULTS

The results indicate that compounds III, IV, and V have more acute and chronic antinociceptive effects than PCP and compound II which may be concerned with more antagonizing activities of these new painkillers for the blockage of dopamine reuptake as well as high affinity for NMDA receptors PCP binding site.

CONCLUSION

It can be concluded that the benzylamine derivative of phencyclidine with a methyl group on the benzyl position on phenyl ring (V) is a more appropriate candidate to reduce acute and chronic (thermal and chemical) pains compared to other substituted phenyl analogs (II-IV) and PCP.

Butenafine and analogues: An expeditious synthesis and cytotoxicity and antifungal activities

The incidence of fungal infections is considered a serious public health problem worldwide. The limited number of antimycotic drugs available to treat human and animal mycosis, the undesirable side effects and toxicities of the currently available drugs, and the emergence of fungal resistance emphasizes the urgent need for more effective antimycotic medicines. In this paper, we describe a rapid, simple, and efficient synthetic route for preparation of the antifungal agent butenafine on a multigram scale. This novel synthetic route also facilitated the preparation of 17 butenafine analogues using Schiff bases as precursors in three steps or less. All the synthesized compounds were evaluated against the yeast, Cryptococcus neoformans/C. gattii species complexes and the filamentous fungi Trichophyton rubrum and Microsporum gypseum. Amine 4bd, a demethylated analogue of butenafine, and its corresponding hydrochloride salt showed low toxicity in vitro and in vivo while maintaining inhibitory activity against filamentous fungi.

Advances in topical and systemic antifungals

Topical antifungal agents are generally used for the treatment of superficial fungal infections unless the infection is widespread, involves an extensive area, or is resistant to initial therapy. Systemic antifungals are often reserved for the treatment of onychomycosis, tinea capitis, superficial and systemic candidiasis, and prophylaxis and treatment of invasive fungal infections. With the development of resistant fungi strains and the increased incidence of life-threatening invasive fungal infections in immunocompromised patients, some previously effective traditional antifungal agents are subject to limitations including multidrug interactions, severe adverse effects, and their fungistatic mechanism of actions. Several new antifungal agents have demonstrated significant therapeutic benefits and have broadened clinicians' choices in the treatment of superficial and systemic invasive fungal infections.

Current use of anti-infectives in dermatology

Dermatologic diseases encompass a broad category of pathologic situations. Infection remains a significant aspect of the pathology faced in patient encounters, and it is natural to expect that anti-infectives play a major element in the armamentarium utilized by dermatologists. Aside from the treatment of the classic bacterial and fungal infections, there are now new uses for antiviral agents to help suppress recurrent disease, such as herpes simplex. There is also the novel approach of using anti-infectives, or agents that have been thought to have antimicrobial activity, to treat inflammatory diseases. This review describes anti-infectives, beginning with common antibiotics used to treat bacterial infections. The discussion will then cover the current use of antivirals. Finally, the description of antifungals will be separated, starting with the oral agents and ending with the topical antimycotics. The use of anti-infectives in tropical dermatology has been purposefully left out, and perhaps should be the subject of a separate review. Cutaneous bacterial infections consist chiefly of those microorganisms that colonize the skin, such as species of staphylococcus and streptococcus. Propionibacterium acnes and certain other anaerobes can be involved in folliculitis, pyodermas and in chronic conditions such as hidradenitis suppurativa.

In vivo fungicidal effect of KP-103 in a guinea pig model of interdigital tinea pedis determined by using a new method for removing the antimycotic carryover effect

We developed a new technique for culture study that successfully recovers fungi from drug-treated skin tissues, in which tissue specimens were homogenized, dialyzed against water, digested with trypsin, and then washed with PBS, to eliminate the drug that remaining in the skin tissue specimens. With this modified culture method, we reevaluated the efficacy of KP-103, neticonazole, and lanoconazole in a guinea pig interdigital tinea pedis model. Guinea pigs with tinea pedis were topically treated with a 1% solution of KP-103 or a reference drug once a day for 10 consecutive days. Five days after the last treatment, left and right feet were subjected to culture study by the conventional and modified recovery culture methods, respectively. One hundred percent (20/20) of lanoconazole-treated feet were judged as culture-negative by the conventional culture method, but 85% (17/20) of the feet were shown to be culture-positive when the modified recovery culture method was used. On the other hand, KP-103 achieved high rates of culture-negative rates, 95% (19/20) and 85% (17/20), in both conventional and modified culture methods, respectively. Furthermore, on day-30 posttreatment, KP-103 sterilized 14 of the 20 infected feet, whereas neticonazole and lanoconazole were not effective even in reducing fungal burden. KP-103 proved to be highly effective in achieving mycological cure and preventing relapse against tinea pedis presumably because of its good bioavailability in the skin based on its low keratin-affinity, along with its potent antifungal activity.

KP-103, a novel triazole derivative, is effective in preventing relapse and successfully treating experimental interdigital tinea pedis and tinea corporis in guinea pigs

The therapeutic efficacy of KP-103, a triazole derivative, for 10 guinea pigs with interdigital tinea pedis or tinea corporis was investigated. Topical KP-103 solution (0.25 to 1%) was dose-dependently effective in treating both dermatophytoses. A 1% KP-103-treatment rendered all infected skins culture-negative on day-2 posttreatment. A high negative-culture rate was obtained with 1% solutions of butenafine and lanoconazole but not with 1% neticonazole solution. The follow up study performed on day-30 and day-9 posttreatment demonstrated that the relapse rates for 1% KP-103-treated animals with tinea pedis and for those with tinea corporis were 20 and 30%, respectively, and that these values were the same as those for 1% butenafine-treated animals, but lower than those for 1% lanoconazole-treated animals (55 and 80%, respectively). When a single dose of 1% KP-103 was applied to the back skin 48 hr before fungal inoculation, 9 of the 10 animals were protected from the dermatophytosis, suggesting that active KP-103 is retained in skin tissue for at least 48 hr after dosing. Moreover, it was suggested that KP-103 retains a high activity in the horny layer because of its lower keratin-affinity. The effectiveness of KP-103 against dermatophytoses may be due to the favorable pharmacokinetic properties in the skin tissues, together with its potent antifungal activity.

Therapeutic efficacy of topically applied KP-103 against experimental tinea unguium in guinea pigs in comparison with amorolfine and terbinafine

The therapeutic efficacy of KP-103, a novel topical triazole, in a guinea pig tinea unguium model was investigated. Experimental tinea unguium and tinea pedis were produced by inoculation of Trichophyton mentagrophytes SM-110 between the toes of the hind paw of guinea pigs. One percent solution (0.1 ml) of KP-103, amorolfine, or terbinafine was topically applied to the nails and whole sole of an infected foot once daily for 30 consecutive days, and terbinafine was also orally administered at a daily dose of 40 mg/kg of body weight for 30 consecutive days, starting on day 60 postinfection. The fungal burdens of nails and plantar skin were assessed using a new method, which makes it possible to recover infecting fungi by removing a carryover of the drug remaining in the treated tissues into the culture medium. Topically applied KP-103 inhibited the development of nail collapse, significantly reduced the fungal burden of the nails, and sterilized the infected plantar skin. On the other hand, topical amorolfine and topical or oral terbinafine were ineffective for tinea unguium, although these drugs eradicated or reduced the fungal burden of plantar skin. The in vitro activities of amorolfine and terbinafine against T. mentagrophytes SM-110 were 8- and 32-fold, respectively, decreased by the addition of 5% keratin to Sabouraud dextrose broth medium. In contrast, the activity of KP-103 was not affected by keratin because its keratin affinity is lower than those of the reference drugs, suggesting that KP-103 largely exists in the nails as an active form that was not bound to keratin and diffuses in the nail without being trapped by keratin. The effectiveness of KP-103 against tinea unguium is probably due to its favorable pharmacokinetic properties in the nails together with its potent antifungal activity.

Butenafine hydrochloride (Mentax) cream for the treatment of hyperkeratotic type tinea pedis and its transfer into the horny layer, with or without concomitant application of 20% urea ointment (Keratinamin)

Forty-five patients were divided into two groups: group I, 23 patients, treated with butenafine hydrochloride (Mentax) cream alone, and group II, 22 patients, treated with butenafine hydrochloride and 20% urea ointment (Keratinamin) to evaluate the usefulness of the treatments. We also measured the transfer of these drugs to the horny layer in some patients. The clinical improvement rate of dermatological symptoms (marked improvement + improvement) was 91.3% in group I, 100% in group II, with therapeutic effects evident earlier in group II than in group I. The mycological eradication rate was found to be 47.4% in group I, 50.0% in group II after 4 weeks of treatment, and 81.8 and 87.5% at 12 weeks thereaftcr. respectively, with no adverse reactions found. The clinical utility rate (markedly useful + useful) was 91.3% in group I and 86.4% in group II. These results demonstrate that application of butenafine hydrochloride alone was extremely effective for the treatment of hyperkeratotic-type tinea pedis and that combination application with urea ointment resulted in an earlier improvement of dermatological symptoms. The concentration of butenafine in the horny layer from healthy volunteers reached a steady state in both groups I and II at 2 weeks after the application, with a lower concentration found in group II (about 70 ng mg(-1)) than in group I (about 100 ng,mg(-1)). Although some variations in concentration were found in case by case, patients in whom the treatment was determined to be 'markedly effective and effective' showed the increase in concentration of the drug in the lesional horny layer to be directly proportional to the number of days of treatment, with a lower concentration found in group II than in group I. This trend was also seen in healthy volunteers.

Experimental and conformational analyses of interactions between butenafine and lipids

Butenafine (N-4-tert-butylbenzyl-N-methyl-1-naphtalenemethylamine hydrochloride) is an antifungal agent of the benzylamine class that has excellent therapeutic efficacy and a remarkably long duration of action when applied topically to treat various mycoses. Given the lipophilic nature of the molecule, efficacy may be related to an interaction with cell membrane phospholipids and permeabilization of the fungal cell wall. Similarly, high lipophilicity could account for the long duration of action, since fixation to lipids in cutaneous tissues might allow them to act as local depots for slow release of the drug. We have therefore used computer-assisted conformational analysis to investigate the interaction of butenafine with lipids and extended these observations with experimental studies in vitro using liposomes. Conformational analysis of mixed monolayers of phospholipids with the neutral and protonated forms of butenafine highlighted a possible interaction with both the hydrophilic and hydrophobic domains of membrane phospholipids. Studies using liposomes demonstrated that butenafine increases membrane fluidity [assessed by fluorescence polarization of 1-(4-trimethylammonium-phenyl)-6-phenyl-1,3,5-hexatriene and 1,6-diphenylhexatriene] and membrane permeability (studied by release of calcein from liposomes). The results show, therefore, that butenafine readily interacts with lipids and is incorporated into membrane phospholipids. These findings may help explain the excellent antifungal efficacy and long duration of action of this drug when it is used as a topical antifungal agent in humans.

In vitro antifungal activity of KP-103, a novel triazole derivative, and its therapeutic efficacy against experimental plantar tinea pedis and cutaneous candidiasis in guinea pigs

The in vitro activity of KP-103, a novel triazole derivative, against pathogenic fungi that cause dermatomycoses and its therapeutic efficacy against plantar tinea pedis and cutaneous candidiasis in guinea pigs were investigated. MICs were determined by a broth microdilution method with morpholinepropanesulfonic acid-buffered RPMI 1640 medium for Candida species and with Sabouraud dextrose broth for dermatophytes and by an agar dilution method with medium C for Malassezia furfur. KP-103 was the most active of all the drugs tested against Candida albicans (geometric mean [GM] MIC, 0.002 microg/ml), other Candida species including Candida parapsilosis and Candida glabrata (GM MICs, 0.0039 to 0.0442 microg/ml), and M. furfur (GM MIC, 0.025 microg/ml). KP-103 (1% solution) was highly effective as a treatment for guinea pigs with cutaneous candidiasis and achieved mycological eradication in 8 of the 10 infected animals, whereas none of the imidazoles tested (1% solutions) was effective in even reducing the levels of the infecting fungi. KP-103 was as active as clotrimazole and neticonazole but was less active than lanoconazole and butenafine against Trichophyton rubrum (MIC at which 80% of isolates are inhibited [MIC(80)], 0.125 microg/ml) and Trichophyton mentagrophytes (MIC(80), 0.25 microg/ml). However, KP-103 (1% solution) exerted therapeutic efficacy superior to that of neticonazole and comparable to those of lanoconazole and butenafine, yielding negative cultures for all samples from guinea pigs with plantar tinea pedis tested. This suggests that KP-103 has better pharmacokinetic properties in skin tissue than the reference drugs. Because the in vitro activity of KP-103, unlike those of the reference drugs, against T. mentagrophytes was not affected by hair as a keratinic substance, its excellent therapeutic efficacy seems to be attributable to good retention of its antifungal activity in skin tissue, in addition to its potency.

Butenafine hydrochloride: for the treatment of interdigital tinea pedis

Butenafine, a derivative of benzylamine with potent fungicidal activity is a new generation of antimycotic compound that has shown to be extremely effective against experimentally-induced tinea pedis in the guinea-pig, a situation that resembles synergetic pathology similar to that of tinea pedis in humans. Butenafine, (N-4-tert-butylbenzyl-N-methyl-1-naphthalenemethyl-amine hydrochloride) with a chemical structure and mode of action similar to those of the allylamines, demonstrates superior fungicidal activity in vitro against dermatophytes and superior fungistatic activity toward Candida albicans that of naftifine and terbinafine. In vitro, pharmacodynamic data has shown that the geometric mean of minimum inhibitory concentration values for butenafine were comparatively lower than those of naftifine and clotrimazole against clinical isolates for many dermatophytes. It inhibits sterol synthesis by blocking the squalene epoxidation stage in fungi. In phramacokinetic assessments butenafine achieves and maintains high concentrations and long retention time in skin, with associated anti-inflammatory activity in vivo. In controlled clinical trials when applied topically, butenafine appears to be well tolerated with a subjective mild burning sensation at the application site. There were no withdrawals from the study. Butenafine is sparingly soluble in water but readily soluble in methanol, ethanol, dichloromethane and chloroform. If incorporated properly in semisolid topical preparations, with a balanced vehicle, butenafine hydrochloride potentially exhibits as a promising alternative antimycotic agent for the treatment of tinea pedis.

The antifungal agent butenafine manifests anti-inflammatory activity in vivo

BACKGROUND

Dermatophyte infections are often accompanied by a striking inflammatory reaction, alleviation of which has often been achieved by the concomitant but controversial use of topical steroidal agents. Recent investigations have suggested the presence of inherent anti-inflammatory properties associated with certain antifungal agents, particularly those within the allylamine class. Butenafine, the first and only approved representative of the benzylamine antifungals, possesses a chemical structure and antifungal activity similar to the allylamines. Although several studies have demonstrated excellent antimycotic efficacy, none has addressed anti-inflammatory properties associated with butenafine.

OBJECTIVE

This study was designed to determine whether butenafine, a benzylamine antifungal, expresses anti-inflammatory activity in vivo.

METHODS

A randomized single-blinded control investigation comparing the attenuation of UVB irradiation-induced erythema by butenafine, its proprietary base cream, and no application (negative control) was performed in humans.

RESULTS

Butenafine demonstrated a significant and marked decrease in UVB-induced erythema as compared with both the base cream and the unaltered control.

CONCLUSION

The benzylamine antifungal agent butenafine demonstrates inherent anti-inflammatory properties, in vivo, as demonstrated by reduced cutaneous erythema response after UVB irradiation.

A randomized trial to assess once-daily topical treatment of tinea corporis with butenafine, a new antifungal agent

BACKGROUND

Tinea corporis treatment usually requires topical application of an antifungal agent for 2 to 3 weeks.

OBJECTIVE

We evaluated short-term treatment of tinea corporis with butenafine hydrochloride, a new benzylamine with in vitro fungicidal activity.

METHODS

Patients (n = 78) were randomly selected to apply butenafine or its cream vehicle alone once daily for 14 days and were periodically assessed until day 42.

RESULTS

Butenafine recipients had significantly higher rates of mycologic cure beginning at day 7 (64% vs 9%) with continued improvements through day 42 (88% vs 17%). They also had higher rates of effective treatment (mycologic cure and 90% to 100% symptom improvement) at day 7 (33% vs 0%) with increasing rates through day 42 (81% vs 14%).

CONCLUSION

Butenafine provides rapid and persistent antifungal activity and symptom relief in patients with tinea corporis. Significant effects were observed within 7 days of therapy initiation, and increasing effectiveness was observed 4 weeks after therapy.

Overview of topical therapy for common superficial fungal infections and the role of new topical agents

Until recently the treatment options for superficial fungal infections have been limited mainly to the use of fungistatic drugs of the imidazole class, discovered in the 1960s. The recent development of allylamine and benzylamine compounds provides antifungal agents with fungicidal mechanisms of action. Both imidazole and allylamine/benzylamine drugs interfere with the production of ergosterol, an essential component of the fungal cell membrane; however, the newer drugs act at an earlier stage of the metabolic pathway than the azoles and cause an accumulation of squalene in the fungal cell, which leads to cell death. In vitro test results show that allylamine/benzylamine minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations (MFCs) are lower than the MICs and MFCs of azoles tested by the same methods. In studies using animal models of dermatophytosis, results have shown the efficacy of the allylamine/benzylamine drugs to be superior to that of azole drugs. Clinical trials have also shown significant differences favoring allylamine/benzylamine drugs over imidazoles in the treatment of dermatophytosis. The fungicidal drugs provide earlier evidence of efficacy, higher cure rates with shorter treatment periods, and lower relapse rates than imidazoles in direct-comparison studies. The allylamine/benzylamine drugs have also shown high cure rates in patients with candidiasis.

Butenafine 1% cream in the treatment of tinea cruris: a multicenter, vehicle-controlled, double-blind trial

BACKGROUND

Butenafine hydrochloride, a potent antifungal agent related to the allylamines, has been used in Japan for treating various cutaneous mycoses including tinea cruris.

OBJECTIVE

We compared the safety and efficacy of butenafine hydrochloride and its vehicle when used once daily for 2 weeks to treat tinea cruris.

METHODS

Patients (n = 93) with tinea cruris and a positive potassium hydroxide examination and mycologic culture were enrolled. Of the 76 patients assessed for efficacy, 37 applied butenafine and 39 applied vehicle once daily for 2 weeks. Assessments were made at the end of the 2-week treatment period and 4 weeks after the end of treatment.

RESULTS

Patients in the butenafine group had a higher mycologic cure rate by day 7 (66% vs 13%, p < 0.0001), with marked improvement 4 weeks after the end of treatment (81% vs 13%, p < 0.0001). They also had a higher rate of effective treatment at day 7 (29% vs 5%, p < 0.01) and at 4 weeks after treatment (73% vs 5%, p < 0.0001). Adverse events definitely related to butenafine treatment were limited to one case of burning sensation after application.

CONCLUSION

Butenafine applied once daily for 2 weeks is effective in treating tinea cruris. The proportion of patients cured increased between the end of treatment and 4 weeks after treatment.

One-week therapy with twice-daily butenafine 1% cream versus vehicle in the treatment of tinea pedis: a multicenter, double-blind trial

BACKGROUND

Butenafine hydrochloride, a benzylamine derivative with potent antifungal activity, has been used in Japan to treat superficial fungal diseases.

OBJECTIVE

We evaluated the safety and efficacy of twice-daily butenafine versus its vehicle in the treatment of interdigital tinea pedis in a multicenter, randomized, double-blind, parallel-group trial.

METHODS

A total of 402 patients with interdigital tinea pedis and a positive potassium hydroxide examination were enrolled. Of the 271 patients who had culture-confirmed tinea pedis and were assessed for efficacy, 132 applied butenafine and 139 applied vehicle twice daily for 1 week. Patients were assessed for mycologic cure, effective treatment, overall cure, and mycologic/clinical cure.

RESULTS

The rates of all four end points were significantly higher with butenafine than with vehicle 5 weeks after treatment ended. Rates of mycologic cure and effective treatment with butenafine were significantly higher than with vehicle at cessation of treatment. Adverse events to treatment occurred in less than 1% of patients treated with butenafine and 2% of patients who applied vehicle.

CONCLUSION

Butenafine applied twice daily for 1 week is highly effective in treating interdigital tinea pedis.

Treatment of interdigital tinea pedis with a 4-week once-daily regimen of butenafine hydrochloride 1% cream

BACKGROUND

Butenafine hydrochloride, a potent new benzylamine with fungicidal activity, has been extensively studied and approved for topical use in Japan. Results reported here are from one of the first major North American butenafine clinical trials.

OBJECTIVE

We evaluated butenafine in the treatment of tinea pedis in a controlled, randomized, double-blind trial.

METHODS

Of 80 patients with positive fungal cultures, 40 applied butenafine 1% cream and 40 applied vehicle to the affected area once daily for 4 weeks. Efficacy was assessed during treatment and 4 weeks after.

RESULTS

Significantly more patients using butenafine than using vehicle had mycologic cure (butenafine, 88%; vehicle, 33%) and effective clinical response (butenafine, 78%; vehicle, 35%). Differences between treatment groups were greatest (p < 0.001) 4 weeks after treatment.

CONCLUSION

Butenafine applied once daily for 4 weeks resulted in an effective clinical response and mycologic cure of tinea pedis during treatment. Patients continued to improve for at least 4 weeks after treatment.

Two mechanisms of butenafine action in Candida albicans

The mechanism of action of a new benzylamine antimycotic, butenafine hydrochloride, was studied in Candida albicans by using the thiocarbamate antimycotic tolnaftate as a reference drug. Butenafine completely inhibited the growth of a test strain of C. albicans at 25 micrograms/ml and was cidal at 50 micrograms/ml. Tolnaftate did not show any growth-inhibitory activity up to 100 micrograms/ml. Both butenafine and tolnaftate inhibited squalene epoxidation in C. albicans, with 50% inhibitory concentrations being 0.57 and 0.17 microgram/ml, respectively. Butenafine, but not tolnaftate, induced the release of appreciable amounts of Pi from C. albicans cells at 12.5 micrograms/ml. This effect of butenafine was augmented when the cells were pretreated with tolnaftate. The results suggest that the direct membrane-damaging effect of butenafine may play a major role in its anticandidal activity and that the drug-induced alteration in the cellular sterol composition renders the cell membrane more susceptible to the membrane-damaging effect of this drug.

Anti-Trichophyton mentagrophytes activity and percutaneous permeation of butenafine in guinea pigs

We examined anti-Trichophyton mentagrophytes activity, cutaneous penetration, and skin localization of butenafine, a novel benzylamine antifungal agent. The following results were obtained. (i) In the guinea pig dorsal skin trichophytosis model, butenafine produced complete eradication of fungi from infected sites. Clotrimazole was active when animals were infected with 10(4) or 10(5) cells but was almost inactive when the inoculum size was 10(6) cells. (ii) The MICs of butenafine and clotrimazole against arthrospores of T. mentagrophytes KD-04 were 0.025 and 0.39 microgram/ml, respectively. (iii) When 0.2 ml of a 1% 14C-butenafine solution was applied for 23 h/day for 7 days, high radioactivity corresponding to 250 to 500 micrograms of butenafine per g of skin in the epidermis, including the horny layer, was observed. (iv) Butenafine penetrates through transepidermal and transfollicular routes. The excellent therapeutic efficacy of butenafine on experimental dermatophytosis may be attributed to its low MIC and good penetration and distribution in the horny layer and hair follicles, where fungi reside.

Topical treatment with butenafine significantly lowers relapse rate in an interdigital tinea pedis model in guinea pigs

Butenafine is a novel antifungal agent of the class of benzylamines. The incidence of relapse after topical treatment with butenafine or bifonazole was investigated in a guinea pig interdigital tinea pedis model. One percent butenafine or bifonazole cream was applied on the infected site of animals for 20 consecutive days starting on day 10 postinfection. On day 30 posttreatment, relapse of the infection occurred in 11 of the 12 feet treated with bifonazole but in only 3 of the 12 feet treated with butenafine. The lower relapse rate after butenafine treatment might be attributable to its potent fungicidal activity and long retention time in the skin.