For therapeutic purposes, fungal infections are classified either as superficial (skin or mucous membranes) or systemic. The former usually respond readily to topical application of an antifungal agent .Systemic fungal infections usually occur in compromised hosts and can be extremely difficult to cure. Relatively high does of antifungal agents prolonged periods of time may be required for these infections and expert advice should be sought for their management.
Nystatin
This is the most commonly prescribed agent for the treatment of Candida infections of skin and mucous membranes. It is not absorbed when given by mouth and cannot be administered parenterally because of its low solubility and toxicity. A suspension, tablets and pessaries are available for the treatment of oral, intestinal and vaginal thrush.
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| * Up to 400 mg daily for several weeks may be necessary in severely immunocompromised patients with invasive fungal infections Invasive fungal infections requiring high doses and prolonged therapy should be treated by physicians with experience of these diseases. In an immunocompromised host (HIV) chronic antifungal secondary prophylaxis may be required. | |
Clotrimazole, econazole, miconazole, isoconazole, sulconazole, tioconazole and ketoconazole
All these belong to the imidazole group of antifungal agents.They are effective against a wide range of fungi. The first two agents are used for the topical therapy of superficial fungal infections. Miconazole and ketoconazole are absorbed from the gut and have been successfully used for the treatment of systemic fungal infections as well as for superficial mycoses. There is also an intravenous formulation of miconazole. Hepatotoxicity (occasionally fatal) has been reported during ketoconazole therapy. Liver function tests should be performed during long-term therapy and ketoconazole should NOT be used for superficial infections.
Fluconazole and itraconazole
Fluconazole is an oral triazole antifungal drug indicated for mucocutaneous and systemic candidiasis and for cryptococcal infections. Itraconazole, also a triazole, is indicated for oropharyngeal and genital candidiasis and for tinea infections. It is contraindicated in liver disease. It has some efficacy in aspergillus infections.
Amphotericin
This is an important antibiotic for the treatment of systemic fungal infections. It is a moderately toxic drug and side, effects are relatively common. These include fever, vomiting, thrombophlebitis, anaemia and nephrotoxicity. The antio is given by intravenous infusion in increasing daily does, usually commencing with 1 mg. A liposomal preparation of amphotericin (AmBisome) is more effective and less toxic, but is very much more expensive; it should only be used in renal failure or in patients who have previously suffered nephrotoxicity with conventional amphotericin.
Flucytosine
This is well absorbed from the gut and side-effects are relatively uncommon, although bone marrow depression can occur. It is active only against yeasts and has been used for the treatment of systemic candidiasis, sometimes in combination with amphotericin. C. albicans can develop resistance to flucytosine.
Griseofulvin
This is concentrated in keratin and is a drug of choice for widespread or chronic dermatophyte infections such as ringworm. It is well absorbed from the gut and is given in a daily dose of 250 mg (child) or 500 mg (adult). Skin lesions respond quickly but infection of the nails requires several months of therapy. Localised and minor ringworm lesions usually respond to topical application of Whitfield's ointment or miconazole.
Terbinafine
The newer agent terbinafine, an allylamine antifungal given in an adult dose of 250 mg daily, is as effective for ringworm when given for 2-4 weeks.