Topical Treatment Of Onychomycosis Research Articles

Nonclinical safety assessment of Efinaconazole Solution (10%) for onychomycosis treatment

Efinaconazole is a triazole developed as a 10% solution for topical treatment of onychomycosis, a common fungal nail infection. Efinaconazole solution and topical formulation vehicle administered dermally to mice (13weeks), rats (6months) and minipigs (9months) produced transient erythema, minimal to modest hyperkeratosis, and mild microscopic skin inflammation. The liver was the target organ of systemic toxicity; reversible, minimal to moderate vacuolated changes were noted in the rat dermal study at 15 and 50mg/kg/day. No systemic toxicity was observed in mice and minipigs, at approximate high dermal doses of 930 and 170mg/kg/day, respectively. Daily subcutaneous injection of propylene glycol vehicle or efinaconazole to rats for 6months produced severe local inflammation and systemic spread, evidenced by peritoneal adhesions, spinal cord necrosis and urinary tract disease. Mortalities occurred in all groups but were increased at the high dose (30 or 40mg/kg/day), suggesting that vehicle effects were exacerbated by efinaconazole. Efinaconazole was not carcinogenic in a 2-year mouse dermal study and was not genotoxic. Exposure-based safety margins at the NOAEL were 70–698 relative to onychomycosis patients. In conclusion, efinaconazole demonstrated low/moderate toxicity, consistent with other azole antifungals, and high safety margins for topical onychomycosis therapy.

Design and development of a safer non-invasive transungual drug delivery system for topical treatment of onychomycosis

Objective: The main objective of this study is to develop a safer non-invasive treatment for nail infections since the current treatment regimen has drawbacks like, incidence of systemic side-effects and higher cost. Proposed topical treatment on the other hand can drastically improve the situation, hence highly desirable. This work was undertaken with a hypothesis to develop a transungual microemulsion gel for topical treatment of onychomycosis.Methods: Benzyl alcohol and isopropyl myristate were used as oil, Pluronic F68 as surfactant and ethanol as co surfactant, in double-distilled water and loading itraconazole as the model antifungal drug. Pseudo-ternary phase diagram was developed by titrating different ratios of total oil and water with total surfactant, and Km ratio was fixed at 1:1. Microemulsion formulations were prepared based on the phase diagram and incorporated in gels by adding Carbopol 934P. Nail permeation enhancers like urea and salicylic acid were used to increase drug permeation through the nail plate. Parameters like drug loading, clarity, particle size distribution, drug entrapment efficiency (DEE), drug release profile, release kinetics and nail uptake were checked for the evaluation of the formulations.Results: Complete release of drug from the formulation varied from 60 to 120 min. The optimized formulation had DEE of 92.75%, complete drug release in 60 min and highest nail uptake of 0.386%/mm2 (39 µg of drug) with 5% urea as nail permeation enhancer.Conclusion: The formulation may prove beneficial in safer treatment of onychomycosis.

In Vitro and In Vivo Assessment of Dermatophyte Acquired Resistance to Efinaconazole, a Novel Triazole Antifungal

Efinaconazole is a novel triazole antifungal drug for the topical treatment of onychomycosis, a nail infection caused mainly by dermatophytes. We assessed the potential of efinaconazole to induce resistance in dermatophytes by continuous exposure of Trichophyton rubrum strains to efinaconazole in vitro (12 passages) and in a guinea pig onychomycosis model (8 weeks). There was no evidence of efinaconazole resistance development in the tested strains under the experimental conditions used.

Luliconazole: a review of a new antifungal agent for the topical treatment of onychomycosis

Luliconazole is a novel, broad-spectrum, imidazole antifungal under development in the USA as a treatment for dermatophytic skin and nail infections. In vitro, luliconazole is one of the most potent antifungal agents against filamentous fungi including dermatophytes. Luliconazole has been formulated in a 10% solution with unique molecular properties, which allow it to penetrate the nail plate and rapidly achieve fungicidal levels in the nail unit. These properties make luliconazole a potent compound in the treatment of onychomycosis. This article reviews the development of luliconazole solution, 10% its molecular properties, preclinical and clinical data and its future perspectives for the treatment of fungal infections.

Topical Treatment of Onychomycosis as a Realistic Option to Systemic Therapy

Onychomycosis is a very common disease, especially in podiatric medical practice. It can be associated with significant patient distress, major disability and pain, and is challenging to treat successfully. This is a case study of a 41-year-old man with distal lateral subungual onychomycosis of 5 years' duration. Forty percent of the great toenail was affected and a total of six toenails were involved. Baseline fungal cultures were positive for Trichophyton rubrum. This patient was treated with efinaconazole 10% solution, a new topical antifungal, once daily for 48 weeks. Mycological cure was noted at the first assessment period (12 weeks), and compete cure was seen at follow-up. This case study alerts physicians to a promising new topical treatment for onychomycosis under development, and to the importance of mycological cure as an early indicator of treatment success.

Transungual delivery of ketoconazole using novel lacquer formulation

Onychomycosis, a common fungal infection of the nail, can have a substantial impact on quality of life. The success of topical therapy for onychomycosis depends on effective penetration, which can be enhanced using an appropriate delivery method. This study evaluated the effectiveness of a novel topical lacquer on enhancing [(14)C]-ketoconazole penetration by comparing nail absorption, nail distribution, and nail penetration of [(14)C]-ketoconazole dissolved in the novel lacquer versus a commercial ketoconazole cream. Using the in vitro finite dose model, the formulations were applied daily to human nail plates for 7 days. Drug absorption was measured by monitoring rate of appearance in each nail layer and the supporting bed. After the multiple day treatment, cumulative concentrations of ketoconazole formulated in novel lacquer in the deep nail layer and the nail bed were significantly greater than cumulative concentrations of commercial ketoconazole (p<0.05), as well as several orders of magnitude greater than the minimal inhibitory concentration (MIC) deemed necessary to inhibit the growth of causative dermatophytic and yeast species. These results suggest that this novel ketoconazole lacquer has the potential to be an effective topical treatment for onychomycosis.

Efinaconazole 10% solution: a new topical antifungal therapy for onychomycosis

Onychomycosis is a common nail infection for which treatment options are limited, and no new treatment have been introduced for over 10 years. While patients might prefer a topical therapy, efficacy with ciclopirox and amorolfine lacquers has been disappointing especially in moderate to severe disease. Efinaconazole 10% solution is a new triazole antifungal, specifically developed for the topical treatment of onychomycosis. Its physicochemical properties, antifungal activity and formulation are all important aspects of the development program and are reviewed here. Efinaconazole 10% solution may provide the first viable alternative to oral therapy for onychomycosis. Mycologic cure rates are comparable to those seen with oral itraconazole, and greater than reported with ciclopirox lacquer.

An assessment of the genetic toxicology of novel boron‐containing therapeutic agents

Boron-containing compounds are being studied as potential therapeutic agents. As part of the safety assessment of these therapeutic agents, a battery of genetic toxicology studies was conducted. The battery included a bacterial reverse mutation (Ames) assay, an in vitro chromosome aberration assay in peripheral human lymphocytes, and an in vivo rat micronucleus study. The following compounds represent some of the boron-containing compounds that have been advanced to human clinical trials in various therapeutic areas. The borinic picolinate, AN0128, is an antibacterial compound with anti-inflammatory activity that has been studied in clinical trials for acne and the treatment of mild to moderate atopic dermatitis. AN2690 (tavaborole) is a benzoxaborole in Phase 3 clinical trials for the topical treatment of onychomycosis, a fungal infection of the toenails and fingernails. Another benzoxaborole derivative, AN2728, a phosphodiesterase-4 (PDE4) inhibitor, is in Phase 2 clinical trials for the treatment of atopic dermatitis. AN2898, also a PDE4 inhibitor, has been studied in clinical trials for atopic dermatitis and psoriasis. AN3365 is a leucyl-tRNA synthetase inhibitor that has been in clinical development for the treatment of various Gram-negative bacterial infections. These five representative compounds were negative in the three genotoxicity assays. Furthermore, AN2690 has been studied in mouse and rat 2-year bioassays and was not found to have any carcinogenic potential. These results demonstrate that it is possible to design boron-based therapeutic agents with no genetic toxicology liabilities.

Ciclopirox delivery into the human nail plate using novel lipid diffusion enhancers

Context: Onychomycosis is a common fungal infection of the nail plate and bed that affects up to 14% of the population and can have a substantial impact on the quality of life of those affected.Objective: This study compared the onychopharmacokinetics, nail absorption, nail distribution, and nail penetration of [14C]-ciclopirox dissolved in novel lipid diffusion enhancers with that of a commercial ciclopirox nail lacquer using the in vitro finite dose model.Materials and methods: The penetration rate of ciclopirox was determined by applying doses of topical formulation twice daily to human nail plates for 11 d. Drug absorption was then measured by monitoring its rate of appearance in each nail layer and in the cotton pad/nail supporting bed.Results: After a multiple day treatment, cumulative concentrations of ciclopirox formulated with lipid enhancers in the deep nail layer and the nail bed were significantly greater than cumulative concentrations of the commercial ciclopirox lacquer (p < 0.001) as well as several orders of magnitude greater than the minimal inhibitory concentration (MIC) deemed necessary to inhibit the growth of the causative dermatophyte species.Conclusion: When formulated with lipid enhancers, the amount of ciclopirox in the ventral/intermediate layer and supporting bed dramatically exceed the inhibitory concentration of ciclopirox for the most common onychomycosis organisms. These results suggest that topical ciclopirox with lipid enhancers has the potential to be an effective topical treatment for onychomycosis, and the lipidic pathway of the nail can be utilized as a means of effective transungual delivery.

Efficacy, Safety and Tolerability of an Optimized Avulsion Technique with Onyster® (40% Urea Ointment with Plastic Dressing) Ointment Compared to Bifonazole-Urea Ointment for Removal of the Clinically Infected Nail in Toenail Onychomycosis: a Randomized Evaluator-Blinded Controlled Study

Background: Toenail onychomycosis is highly prevalent, with 14-28% of people aged 60 or over suffering from the disease. Use of a topical antifungal alone in toenail onychomycosis is associated with low cure rates. This may be due to limited penetration of the topical antifungal through the diseased nail. The objective of the present study was to compare two treatment modalities to obtain diseased nail chemical avulsion in toenail onychomycosis. Methods: In this European, multicenter, randomized, parallel-group, open-label, active-controlled study, male or female adult patients with distal-lateral or lateral subungual dermatophyte onychomycosis on at least 12.5% of the great toenail were randomized either to a 40% urea ointment with plastic dressing group (n = 53) or to a bifonazole-urea ointment group (n = 52). The ointments were applied daily for a maximum of 3 weeks according to the summary of product characteristics. After assessment of infected nail debridement, topical antifungal treatment with bifonazole cream was applied daily in both groups for 8 weeks. 102 patients were evaluated, i.e. 51 in the 40% urea ointment with plastic dressing group and 51 in the bifonazole-urea group. The primary end point was complete removal of the nail plate at day 21 (D21). Secondary end points were: complete cure and mycological cure evaluated at D105. Ease of use and local tolerability were also assessed. Results: Complete removal of the clinically infected target nail plate area, assessed by blinded evaluators, was significantly higher in the 40% urea ointment with plastic dressing group (61.2%) than in the control group (39.2%), showing the superiority of 40% urea ointment with plastic dressing (p = 0.028). The same results were observed in the per-protocol population (63.0 vs. 36.6%; p = 0.014). Complete removal of the infected area assessed by the investigator at D21 showed a significantly higher success rate in patients treated with 40% urea ointment with plastic dressing (86.3%) as compared to patients treated with bifonazole-urea (60.8%), confirming the superiority of 40% urea ointment with plastic dressing (p = 0.004). At D105, the complete cure of onychomycosis, a criterion combining clinical and mycological assessments, showed a success rate of 27.7% for 40% urea ointment with plastic dressing versus 20.8% for the control group. No statistical difference was observed between the two treatment groups. The number of patients with at least one adverse event was twice as high in the bifonazole-urea group in comparison to the 40% urea ointment with plastic dressing group. Overall assessment of local tolerability by the investigator was considered good/very good in 98.0% of the 40% urea ointment with plastic dressing patients versus 90.4% of the bifonazole-urea patients, at D21, with no significant difference between both groups. Conclusion: This study shows the superiority of 40% urea ointment with plastic dressing to bifonazole-urea ointment for complete removal of the infected target nail assessed by blinded evaluators and by the investigators. Further studies are needed to assess the impact of preliminary chemical nail avulsion on the efficacy of topical treatment of onychomycosis as assessed by complete cure at 1 year.

Terbinafine nail solutions for topical treatment of onychomycosis: Ex vivo study on penetration/retention through and into keratin membranes

Terbinafine nail solutions for topical treatment of onychomycosis: Ex vivo study on penetration/retention through and into keratin membranes

Natural coniferous resin lacquer in treatment of toenail onychomycosis: an observational study

In in vitro tests, natural coniferous resin from the Norway spruce (Picea abies) is strongly antifungal. In this observational study, we tested the clinical effectiveness of a lacquer composed of spruce resin for topical treatment of onychomycosis. Thirty-seven patients with clinical diagnosis of onychomycosis were enrolled into the study. All patients used topical resin lacquer treatment daily for 9 months. A mycological culture and potassium hydroxide (KOH) stain were done from nail samples in the beginning and in the end of the study. Treatment was considered effective, if a mycological culture was negative and there was an apparent clinical cure. At study entry, 20 patients (20/37; 54%; 95% CI: 38–70) had a positive mycological culture and/or positive KOH stain for dermatophytes. At study end, the result of 13 patients was negative (13/19; 68%; 95% CI: 48–89). In one case (1/14; 7%; 95% CI: 0–21) the mycological culture was initially negative, but it turned positive during the study period. By 14 compliant patients (14/32; 44%; 95% CI: 27–61), resin lacquer treatment was considered clinically effective: complete healing took place in three cases (9%) and partial healing in 11 cases (85%). The results indicate some evidence of clinical efficacy of the natural coniferous resin used for topical treatment of onychomycosis.

Therapeutic potential of TDT 067 (terbinafine in Transfersome®): a carrier-based dosage form of terbinafine for onychomycosis

Introduction: Current topical treatments for onychomycosis are unsatisfactory. New topical agents that offer efficacy without the potential adverse effects of oral antifungal therapy would benefit patients with this condition and encourage a greater treatment rate.Areas covered: Currently available topical therapies are reviewed, and new approaches for enhancing delivery of the established antifungal terbinafine through the nail are summarized. We focus on the use of ultra-deformable lipid vesicles to facilitate delivery of terbinafine to the nail and surrounding tissue. TDT 067 (terbinafine in Transfersome®) is the only such therapy in development for onychomycosis, and we review published preclinical and clinical studies on this formulation.Expert opinion: TDT 067 offers the use of new technology to deliver an established antifungal, terbinafine. Preclinical data suggest that the Transfersome® accelerates entry of terbinafine released from TDT 067 into fungi and potentiates its antifungal effects, resulting in enhanced activity, compared with conventional terbinafine. This translated into high rates of mycological cure and evidence of clinical effect in a study of TDT 067 administered twice daily for 12 weeks in patients with onychomycosis. An ongoing Phase-III trial involving more than 700 patients treated for 48 weeks is investigating the efficacy and safety of TDT 067.

Double blind clinical trial of the Ageratina pichinchensis extract in the topical treatment of onychomycosis

Onychomycosis is a high-prevalence infectious disease that is usually treated with drugs administered chronically via the oral pathway, which produce important side effects. Ageratina pichinchensis, used in traditional medicine to treat dermatophytosis, has shown antifungal activity against Thrichophyton rubrum, and T. mentagrophytes. Clinically, a nail lacquer elaborated with the extract obtained from this plant showed similar rates of therapeutic effectiveness than 8% ciclopirox in patients with onichomycosis. OBJECTIVE: Evaluate two different concentrations of the standardized extract of A. pichinchensis in patients with mild to moderate onychomycosis. METHODOLOGY: By means of a randomly and comparative double blind clinical trial, 122 patients of either sex, within 19 and 65 years were included. A toenail sample was taken and submitted to direct microscopic identification before and after treatment. Two experimental groups were organized; group 1 was administered with a cosmetic nail lacquer formulation containing a 12.6% A. pichinchenis extract, while group 2 received an identical product containing 16.8% A. pichinchenis extract. All patients were treated and followed clinically for 6 months by means of monthly appointments. ANOVA and X2 test were employed to identify differences between groups. Values of p<0.05 were considered significant. Results: 103 patients concluded the treatment. The therapeutic effectiveness exhibited by the 12.6% formulation was 67.2% while that of the 16.8% was 79.1%. Regarding clinical evolution analysis of results at the end of the treatment evidenced that the 16.8% concentration possesses higher therapeutic effectiveness (p=0.01).

Double blind clinical trial of the ageratina pichinchensis extract in the topical treatment of onychomycosis

Onychomycosis is a high-prevalence infectious disease that is usually treated with drugs administered chronically via the oral pathway, which produce important side effects. Ageratina pichinchensis, used in traditional medicine to treat dermatophytosis, has shown antifungal activity against Thrichophyton rubrum, and T. mentagrophytes. Clinically, a nail lacquer elaborated with the extract obtained from this plant showed similar rates of therapeutic effectiveness than 8% ciclopirox in patients with onichomycosis. OBJECTIVE: Evaluate two different concentrations of the standardized extract of A. pichinchensis in patients with mild to moderate onychomycosis. METHODOLOGY: By means of a randomly and comparative double blind clinical trial, 122 patients of either sex, within 19 and 65 years were included. A toenail sample was taken and submitted to direct microscopic identification before and after treatment. Two experimental groups were organized; group 1 was administered with a cosmetic nail lacquer formulation containing a 12.6% A. pichinchenis extract, while group 2 received an identical product containing 16.8% A. pichinchenis extract. All patients were treated and followed clinically for 6 months by means of monthly appointments. ANOVA and X2 test were employed to identify differences between groups. Values of p<0.05 were considered significant. Results: 103 patients concluded the treatment. The therapeutic effectiveness exhibited by the 12.6% formulation was 67.2% while that of the 16.8% was 79.1%. Regarding clinical evolution analysis of results at the end of the treatment evidenced that the 16.8% concentration possesses higher therapeutic effectiveness (p=0.01).

A comparative evaluation of combination therapy of fluconazole 1% and urea 40% compared with fluconazole 1% alone in a nail lacquer for treatment of onychomycosis: therapeutic trial

This is a randomized, double-blind study enrolling 70 patients with onychomycosis of the finger and toenails. Clinical and mycological efficacies as well as measures of safety were assessed monthly for a maximum of 6 months of treatment. The treatment regimens were: fluconazole 1% and fluconazole 1% with urea 40%. These results indicated topical treatment of onychomycosis with a combination of fluconazole 1% and urea 40% was more effective (82.8%) than fluconazole 1% (62.8%) nail lacquer alone in treatment of dermatophytic onychomycosis. Fluconazole was well tolerated and side effects were negligible. At the end of therapy and the end of the 6-month follow-up, fluconazole 1% and urea 40% demonstrated statistically significant superiority in clinical and mycological responses compared with fluconazole 1% alone.

Activity of TDT 067 (Terbinafine in Transfersome) against Agents of Onychomycosis, as Determined by Minimum Inhibitory and Fungicidal Concentrations

TDT 067 is a novel carrier-based dosage form (liquid spray) of 15 mg/ml of terbinafine in Transfersome that has been developed to deliver terbinafine to the nail bed to treat onychomycosis. In this study, we report the in vitro activities of TDT 067 against dermatophytes, compared with those of the Transfersome vehicle, naked terbinafine, and commercially available terbinafine (1%) spray. The MICs of TDT 067 and comparators against 25 clinical strains each of Trichophyton rubrum, T. mentagrophytes, and Epidermophyton floccosum were determined according to the CLSI M38-A2 susceptibility method (2008). Minimum fungicidal concentrations (MFCs) were determined by subculturing visibly clear wells from the MIC microtiter plates. TDT 067 demonstrated potent activity against the dermatophyte strains tested, with an MIC range of 0.00003 to 0.015 μg/ml. Overall, TDT 067 MIC(50) values (defined as the lowest concentrations to inhibit 50% of the strains tested) were 8-fold and 60-fold lower than those of naked terbinafine and terbinafine spray, respectively. The Transfersome vehicle showed minimal inhibitory activity. TDT 067 demonstrated lower MFC values for T. rubrum and E. floccosum than naked terbinafine and terbinafine spray. TDT 067 has more potent antifungal activity against dermatophytes that cause nail infection than conventional terbinafine preparations. The Transfersome vehicle appears to potentiate the antifungal activity of terbinafine. Clinical investigation of TDT 067 for the topical treatment of onychomycosis is warranted.

Hydrosoluble medicated nail lacquers: in vitro drug permeation and corresponding antimycotic activity

Two nail lacquers, containing ciclopirox (CPX) or amorolfine (MRF), based on water-insoluble polymers are currently considered mainstays of topical treatment of onychomycosis. The present study aimed at evaluating the antimycotic activity of a new water-soluble nail lacquer containing CPX (CPX/sol), easily removable by washing with water and applicable to periungual skin. To compare transungual permeation of CPX with that of MRF in the same hydroxypropyl chitosan-based nail lacquer (MRF/sol) and with a nonwater-soluble reference (Loceryl); Galderma International, La Défense, France), and to evaluate the antimycotic activity of CPX/sol and Loceryl against the most common fungal strains that cause onychomycosis. Methods In vitro drug permeation experiments with CPX/sol, MRF/sol and Loceryl were carried out through bovine hoof slices. Experimental permeates from CPX/sol and Loceryl underwent in vitro susceptibility testing against clinical isolates of dermatophytes, moulds and yeast. Results MRF transungual flux from MRF/sol lacquer was significantly higher when compared with Loceryl. CPX was able to permeate hoof membranes more easily compared with MRF. CPX and MRF concentrations in the subungual fluids collected after application of CPX/sol or Loceryl were sufficient to inhibit fungal growth, with the exception of Candida parapsilosis. Smaller amounts of fluid containing CPX were required for complete inhibition of fungal growth. Efficacy index values were significantly higher for CPX/sol. Conclusions Application of the CPX/sol nail lacquer allows rapid nail penetration of CPX, providing CPX levels sufficient to inhibit fungal growth for a prolonged period of time (30 h) after application of lacquer dose. CPX/sol nail lacquer appeared superior to the market reference Loceryl in terms of both vehicle (hydroxypropyl chitosan) and active ingredient (CPX) as witnessed by its higher efficacy on all nail pathogens.

Clinical trial to compare the effectiveness of two concentrations of the Ageratina pichinchensis extract in the topical treatment of onychomycosis

The plant species Ageratina pichinchensis has been used, for many years, in Mexican traditional medicine for the treatment of superficial mycosis. Aim of the study This study compared the therapeutic effectiveness and tolerability of two concentrations of the standardized extract from Ageratina pichinchensis (12.6 and 16.8%) on patients with clinical and mycological diagnosis of mild and moderate onychomycosis. Materials and methods Two identical phytopharmaceuticals (containing the standardized extract from Ageratina pichinchensis) in nail lacquer solution for topical administration were evaluated in a double-blind clinical trial. Treatments were administered for 6 months to patients distributed in two groups. Results and discussion Of 122 patients who agreed to participate in the study, 103 (84.4%) concluded the treatment. The therapeutic effectiveness exhibited by the 12.6% Ageratina pichinchensis extract was 67.2%, while that of the 16.8% Ageratina pichinchensis extract was 79.1%. Regarding clinical evolution, analysis of results at the end of treatment evidenced that the 16.8% concentration possesses higher therapeutic effectiveness with a significant statistical difference ( p = 0.010). No treatment produced side effects. Conclusion Both concentrations of phytopharmaceuticals possess high rates of effectiveness on patients with mild and moderate onychomycosis, and the formulation with a 16.8% concentration possesses higher effectiveness.

Determination of the efficacy of terbinafine hydrochloride nail solution in the topical treatment of dermatophytosis in a guinea pig model

Currently available topical antifungals are often not satisfactory for the treatment of nail infections, because of the inability to penetrate the nail plate. Terbinafine HCl nail solution is a novel antifungal formulation containing a nail penetration enhancer dodecyl-2-N,N-dimethylaminopropionate hydrochloride (DDAIP HCl, trade name NexACT-88). In this study, we used a guinea pig model of Trichophyton mentagrophytes dermatophytosis and evaluated the clinical and mycological efficacy of different terbinafine HCl nail solutions (TNS) formulated with or without DDAIP HCl. Ciclopirox (8%) nail lacquer (Penlac), the only Food and Drug Administration approved topical treatment for onychomycosis, was used as a comparator. Following the IACUC Guidelines, the skin of male albino guinea pigs was abraded under anaesthesia. Each animal was infected with T. mentagrophytes ATCC 24953 (cell suspension containing 1 x 10(7) conidia). The experimental animals were divided into 11 groups (five animals per group) and tested with the following formulations: vehicle control, 0.5% DDAIP HCl, 1%, 5% and 10% TNS (without DDAIP HCl), 1% TNS with 0.5%, 2.5% and 5.0% DDAIP HCl, 5% and 10% TNS with 0.5% DDAIP HCl, 8% ciclopirox nail lacquer and an untreated control group. Evaluation of clinical and mycological efficacy was performed 72 h after completion of a 7-day treatment regimen. Skin biopsy samples were processed for histopathological examination. The infected untreated control guinea pigs showed patches of hair loss and ulcerated or scaly skin and fungal invasion of hair roots. The vehicle and 0.5% DDAIP HCl treated groups showed minimal clinical efficacy (only 11% and 5%, respectively). In contrast, all three concentrations of TNS (1%, 5% and 10% terbinafine HCl) formulated with or without 0.5% DDAIP HCl showed 100% mycological efficacy by the hair root invasion test. Clinical efficacy of the 5% and 10% TNS improved with addition of 0.5% DDAIP HCl (47.4% and 73.8% vs. 68.4% and 89.5%, respectively). In addition, no fungal elements were detected in the treated guinea pig skin. All formulations of TNS resulted in a higher clinical and mycological efficacy compared with the 8% ciclopirox nail lacquer (P = 0.0444). In conclusion, TNS containing 1%, 5% and 10% terbinafine HCl formulated with and without DDAIP HCl demonstrated high antifungal efficacy in experimental dermatophytosis. Addition of 0.5% DDAIP HCl to 5% and 10% TNS significantly enhanced the clinical and mycological efficacy of these formulations which were superior compared with the 8% ciclopirox nail lacquer. Evaluation of the 1%, 5% and 10% TNS in clinical trials for the treatment of dermatophytosis and onychomycosis is warranted.