The newer
antifungal agents itraconazole,
terbinafine and
fluconazole have become available to treat
onychomycosis over the last 10 years. During this time period these agents have superseded
griseofulvin as the agent of choice for
onychomycosis. Unlike
griseofulvin, the new agents have a broad spectrum of action that includes dermatophytes, Candida species and nondermatophyte moulds. Each of the 3 oral
antifungal agents,
terbinafine,
itraconazole and
fluconazole, is effective against dermatophytes with relatively fewer data being available for the treatment of Candida species and nondermatophyte moulds.
Itraconazole is effective against Candida
onychomycosis.
Terbinafine may be more effective against C. parapsilosis compared with C. albicans; furthermore with Candida species a higher dose of
terbinafine or a longer
duration of therapy may be required compared with the regimen for dermatophytes. The least amount of experience in treating
onychomycosis is with
fluconazole.
Griseofulvin is not effective against Candida species or the nondermatophyte moulds. The main use of griseo-fulvin currently is to treat
tinea capitis.
Ketoconazole may be used by some to treat
tinea versicolor with the dosage regimens being short and requiring the use of only a few doses. The preferred regimens for the 3 oral antimycotic agents are as follows:
itraconazole - pulse
therapy with the
drug being administered for 1 week with 3 weeks off treatment between successive pulses;
terbinafine - continuous once daily
therapy; and
fluconazole - once weekly treatment. The regimen for the treatment of dermatophyte
onychomycosis is:
itraconazole - 200mg twice daily for I week per month x 3 pulses;
terbinafine - 250 mg/day for 12 weeks; or,
fluconazole - 150 mg/wk until the abnormal-appearing nail plate has grown out, typically over a period of 9 to 18 months. For the 3 oral
antifungal agents the more common adverse reactions pertain to the following systems, gastrointestinal (for example,
nausea, gastrointestinal distress, diarrhoea,
abdominal pain), cutaneous eruption, and CNS (for example,
headache and malaise). Each of the new
antifungal agents is more cost-effective than
griseofulvin for the treatment of
onychomycosis and is associated with high compliance, in part because of the shorter
duration of therapy. The newer
antifungal agents are generally well tolerated with drug interactions that are usually predictable.