Safety review of the oral antifungal agents used to treat superficial mycoses

Treatment of Onychomycosis: Pros and Cons of Antifungal Agents

Background:

Antifungal agents are beneficial in the treatment of onychomycosis in the general population, as well as in children, the elderly, and immunocompromised individuals. Special patient populations can be more difficult to treat due to such factors as drug interactions with concomitant medications, adverse events, and poor compliance. In addition, there is limited information about the use of antifungal agents in special populations, e.g., children.

Objective:

The pros and cons of oral and topical antifungal agents are discussed, with focus on special patient populations.

Methods:

We searched MedLine (1966 to April 2003) for clinical studies evaluating the efficacy of oral and topical antifungal agents to treat onychomycosis. The key words used in conjunction with “onychomycosis” include: “terbinafine,” “itraconazole,” “fluconazole,” “amorolfine nail lacquer,” “ciclopirox nail lacquer,” “HIV,” “transplant patients,” “diabetes,” “children,” and “elderly.” Studies were excluded if published in a language other than English.

Results:

Studies have shown that antifungal agents can be of benefit in treating the elderly, children, and immunocompromised individuals (e.g., transplant patients, Down's patients, HIV patients, and diabetics) with onychomycosis.

Conclusion:

The treatment modality of onychomycosis in special patient populations should take into account the clinical presentation of the onychomycosis, the causative organism, patient and physician preference, the concomitant medications that the patient is on, and the potential for adverse events for that patient if antifungal therapy is undertaken.

Onychomycosis: beyond cosmetic distress

Onychomycosis, or fungal infection of the nail, is the most common nail disease affecting children (although to a lesser extent) as well as adults. The distress it provokes is not only of a cosmetic kind; it may impair the quality of life. The different clinical types of onychomycosis should be differentiated from similar-looking nail diseases. As far as therapy is concerned, the appearance of new antifungal drugs in the 1990s makes our job easier, but it does not allow us to cure 100% of the patients. Relapses still exist. The aim of this article is to help dermatologists achieve a tailor-made treatment for their patients. The clinical type, the compulsory mycological investigations, the age of the patient, his medical history (drug intake), as well as the use of nail cosmetics, must be considered.

Terbinafine: a review of its use in onychomycosis in adults

Terbinafine, an orally and topically active antimycotic agent, inhibits the biosynthesis of the principal sterol in fungi, ergosterol, at the level of squalene epoxidase. Squalene epoxidase inhibition results in ergosterol-depleted fungal cell membranes (fungistatic effect) and the toxic accumulation of intracellular squalene (fungicidal effect). Terbinafine has demonstrated excellent fungicidal activity against the dermatophytes and variable activity against yeasts and non-dermatophyte molds in vitro. Following oral administration, terbinafine is rapidly absorbed and widely distributed to body tissues including the poorly perfused nail matrix. Nail terbinafine concentrations are detected within 1 week after starting therapy and persist for at least 30 weeks after the completion of treatment. Randomized, double-blind trials showed oral terbinafine 250 mg/day for 12 or 16 weeks was more efficacious than itraconazole, fluconazole and griseofulvin in dermatophyte onychomycosis of the toenails. In particular, at 72 weeks' follow-up, the multicenter, multinational, L.I.ON. (Lamisil vs Itraconazole in ONychomycosis) study found that mycologic cure rates (76 vs 38% of patients after 12 weeks' treatment; 81 vs 49% of recipients after 16 weeks' therapy) and complete cure rates were approximately twice as high after terbinafine treatment than after itraconazole (3 or 4 cycles of 400 mg/day for 1 week repeated every 4 weeks) in patients with toenail mycosis. Furthermore, the L.I.ON. Icelandic Extension study demonstrated that terbinafine was more clinically effective than intermittent itraconazole to a statistically significant extent at 5-year follow-up. Terbinafine produced a superior complete cure rate (35 vs 14%), mycologic cure rate (46 vs 13%) and clinical cure rate (42 vs 18%) to that of itraconazole. The mycologic and clinical relapse rates were 23% and 21% in the terbinafine group, respectively, compared with 53% and 48% in the itraconazole group. In comparative clinical trials, oral terbinafine had a better tolerability profile than griseofulvin and a comparable profile to that of itraconazole or fluconazole. Post marketing surveillance confirmed terbinafine's good tolerability profile. Adverse events were experienced by 10.5% of terbinafine recipients, with gastrointestinal complaints being the most common. Unlike the azoles, terbinafine has a low potential for drug-drug interactions. Most pharmacoeconomic evaluations have shown that the greater clinical effectiveness of oral terbinafine in dermatophyte onychomycosis translates into a cost-effectiveness ratio superior to that of itraconazole, fluconazole and griseofulvin.

CONCLUSION

Oral terbinafine has demonstrated greater effectiveness than itraconazole, fluconazole and griseofulvin in randomized trials involving patients with onychomycosis caused by dermatophytes. The drug is generally well tolerated and has a low potential for drug interactions. Therefore, terbinafine is the treatment of choice for dermatophyte onychomycosis.

Current Management of Onychomycosis and Dermatomycoses

Three newer oral antifungal agents, itraconazole, terbinafine and fluconazole, have revolutionized treatment of superficial mycoses. The tissue pharmacokinetics of itraconazole and terbinafine allow much shorter courses of therapy- with higher efficacy-in the treatment of onychomycosis, compared to other oral agents. Itraconazole pulse dosing and terbinafine daily dosing have shown comparable efficacy against dermatophyte onychomycosis; similar itraconazole regimens have been effective against nondermatophyte infections. Refractory clinical patterns of nail disease appear to be more responsive to oral antifungal therapy when combined with adjunctive therapy, such as debridement. These agents are effective against cutaneous dermatophytosis, with shorter treatment regimens. Tinea versicolor may be treated with a single-dose, intermittent, or daily regimen of an oral azole agent, depending on the drug selected. These newer oral antifungal agents have been proven effective against tinea capitis; effective regimens are shorter than those for griseofulvin. The safety profile of these newer agents has been very favorable.