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Terbinafine is an orally and topically active allylamine antifungal drug which is an effective and well tolerated therapy for a wide range of superficial dermatophyte infections. In contrast to most other commonly prescribed antifungal agents, terbinafine is fungicidal in vitro and possesses improved pharmacokinetic properties with respect to drug penetration into nail tissue following oral administration. These properties enable terbinafine to achieve high success rates with shortened therapy regimens in the treatment of dermatophyte skin infections and onychomycosis.
Pharmacoeconomic analyses have shown that oral terbinafine, with its higher rates of clinical efficacy and lower rates of relapse/reinfection, is less costly and more cost effective than oral griseofulvin, ketoconazole and itraconazole when used as initial therapy in the treatment of onychomycosis. However, some points regarding the clinical efficacy of itraconazole relative to terbinafine and the drug treatment regimens used in these studies need further clarification.
In the management of tinea pedis, a cost analysis suggested that initial therapy with terbinafine 1% cream was more costly than initial therapy with miconazole, oxiconazole or clotrimazole. However, in cost-effectiveness studies, terbinafine had a lower cost per disease-free day than ciclopirox, clotrimalzole, ketoconazole and miconazole in the treatment of dermatophyte skin infections.
In conclusion, available clinical and pharmacoeconomic data support the use of topical terbinafine as first-line treatment of dermatophyte skin infections unless the acquisition cost of terbinafine is markedly greater, than that of alternative topical antifungal agents. Oral terbinafine can be recommended as a cost-effective first-line treatment, preferable to oral griseofulvin, ketoconazole and itraconazole, in patients with dermatophyte onychomycosis.
Disease and Treatment Considerations
Superficial fungal infections caused by detmatophyte fungi are prevalent in the general population and have been called the most common infectious disease. These infections can be disfiguring and painful and can adversely impact on quality of life (most notably in patients with onychomycosis). They are associated with substantial treatment costs.
Detmatophytoses such as tinea pedis. tinea cruris and tinea corporis typically respond to treatment with topical antifungal agents (e.g. miconazole, tolnaftate. clotrimazole, naftifine and ketoconazole) applied twice daily for up to 4 weeks. with efficacy rates generally >80%. However, noncompliance with full treatment courses is common. Extensive or recalcitrant dennatophyte infections such as onychomycosis and severe forms of tinea pedis (e.g. plantar- or moccasin-type tinea pedis) require therapy with oral antifungal drugs.
Terbinafine is an orally and topically active allylamine antifungal drug. In contrast to the in vitro fungistatic activities of griseofulvin, ketoconazole, itraconazole and most other antifungal drugs, terbinafine is fungicidal in vitro. It also penetrates well into nails, maintaining high concentrations for at least 55 days after discontinuation of oral therapy which allows for continued clinical resolution of infection even after the completion of a course of treatment. These properties enable terbinafine to achieve high efficacy rates in the treatment of superficial fungal infections, even with shortened treatment regimens.
In the treatment of dennatophyte nail infections, clinical trials have shown that oral terbinafine (250 mg/day for 12 to 24 weeks) is effective and well tolerated, producing success rates (both clinical and mycological cure) in approximately 80 and 95% of patients, respectively, with toenail and fingernail mycoses. In recent comparative trials, terbinafine 250 mg/day for 12 and 16 weeks. respectively, achieved significantly higher success rates than griseofulvin 500 mg/day for 12 weeks (76 vs 39%) in the treatment of fingernail dermatophyte infections and imennittent itraconazole 400 mg/day for 1 of 4 weeks for 16 weeks (76 vs 35%) in the treatment of toenail and fingernail dermatophyte infections.
Oral terbinafine has also demonstrated good clinical and mycological efficacy in the treatment of tinea pedis. including more extensive infections (e.g. plantar-type tinea pedis). Rates of mycological cure with 2 weeks’ treatment with terbinafine 250 mg/day (range 78 to 89%) were similar to those with 4 weeks’ treatment with itraconazole 100 mg/day (69 to 81%), and were significantly higher than 2 weeks’ treatment with itraconazole 100 mg/day (86 vs 55%). Treatment relapses appeared to be less frequent in terbinafine recipients.
In patients with dermatophyte skin infections, terbinafine 1 % cream administered for 2 to 4 weeks produces mycological cure and clinical efficacy rates of 93% and approximately 80%, respectively. Similar cure r ates have been achieved with treatment periods of 1 to 2 weeks. Furthermore, in 2 recent comparative trials, a 1-week course of terbinafine 1 % cream produced higher mycological cure rates than a 4-week course of clotrimazole 1 % cream (97 vs 84% at 6 weeks in 1 study and 83 vs 66% at 12 weeks in the other) in patients with tinea pedis.
The pharmacoeconomics of oral terbinafine in the treatment of onychomycosis have been assessed in payer-perspective studies. Projected costs of oral terbinafine therapy and disease management (with all patients being treated with terbinafine by their general practitioners) were about half of those associated with treatment with griseofulvin in patients referred to a dermatology clinic in a UK cost analysis. This difference was due to the lower physician costs (avoidance of further dermatology clinic disease management) as well as lower drug costs for retreatment due to relapse/reinfection. In a 13-country cost-effectiveness study, which used a decision analysis model to outline all possible treatment outcomes, terbinafine was more cost effective (lower cost per disease-free day) than griseofulvin, ketoconazole and itraconazole in the treatment of both fingernail and toenail onychomycosis. Data from 3 countries (Canada, Germany and The Netherlands) included in this analysis were published separately and were generally consistent with the overall results from the 13-country study. The usefulness of these data are somewhat limited by the fact that the duration, dosage and type of antifungal drug regimens used in the decision analysis model were not clearly stated. Some points regarding the clinical effectiveness of itraconazole relative to terbinafine also require further clarification.
Three studies (1 cost analysis and 2 cost-effectiveness studies) evaluated the pharmacoeconomics of terbinafine 1 % cream in the topical treatment of dermatophyte skin infections. The cost analysis was performed from a purchaser’s perspective and indicated that the initial use of terbinafine for topical therapy of tinea pedis was more costly than initial topical treatment with miconazole, oxiconazole or clotrimazole (even after taking treatment failures with these agents and subsequent treatment with topical terbinafine into consideration). However, 2 cost-effectiveness studies, which used a similar decision analysis model to that described in the 13-country study above, showed that topical terbinafine was more cost effective and produced more disease-free days than topical ciclopirox, clotrimazole, ketoconazole or miconazole in the treatment of dermatophyte skin infections. It is important to note that these cost-effectiveness data (from Canada, Germany, Switzerland and Austria) do not necessarily extrapolate to other countries.
KeywordsItraconazole Ketoconazole Terbinafine Griseofulvin Clotrimazole
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