The extent and nature of diseases caused by fungi (mycoses) vary a great deal between different areas of the world. In some areas fungal diseases are regularly present in the community, whereas in other areas they only occur under certain circumstances, for example, in individuals who have immune deficiency and in whom resistance to infection is reduced. This may occur because of drug treatments or disease.

Fungal infections are spread by spores or hyphae. Normally they are breathed in or land on the skin to cause infection. From the skin and lungs the fungus may spread to other parts of the body. Fungal infections last a long time (they are chronic infections) and usually any drug treatment has to be prolonged in order to obtain a cure.

Local fungal infections of the skin, mouth, vagina or anus are usually associated with some local damage to the surface or to treatment with antibiotics. The latter disturbs the local balance of bacteria and fungi and makes it easier for fungus to start to grow. A common example of this is vaginal thrush in someone given antibiotics by mouth. Some patients may be allergic to fungi and develop asthma and other respiratory disorders.

Because fungi particularly attack patients who are immune-deficient it is important to treat the ‘whole’ patient in order to correct if possible any predisposing factors. Any anaemia, infection or other underlying disorder should be treated and the patient should be given vitamins, minerals and a nutritious diet. Also, it is important to remove any contact with an infected animal, whether it is a dog, farm animal, pigeon or even bats in a cave.

Antifungal drugs include:

• Amorolfine (Loceryl Cream and Nail Laquer)
• amphotericin (Abelcet, AmBisome, Amphocil, Fungilin, Fungizone)
• clotrimazole (in topical applications (Canesten, Candiden))
• econazole (in topical applications (Ecostatin, Pevaryl))
• fluconazole (Diflucan)
• flucytosine (Ancotil)
• griseofulvin (Grisovin)
• itraconazole (Sporanox)
• ketoconazole (Nizoral and in topical applications (Nizoral))
• miconazole (Daktarin and in topical applications (Daktarin))
• nystatin (Nystan and in several topical applications (Nystaform, Nystan, Tinaderm M))
• terbinafine (Lamisil and in topical applications (Lamisil))
• tioconazole (Trosyl nail solution)

Antifungal drugs may be grouped according to their chemical structure –

allylamines (terbinafine)

griseofulvin, imidazoles (e.g. clotrimazole, ketoconazole, tioconazole, miconazole)

polyene antibiotics (e.g. amphotericin, nystatin)

triazoles (itraconazole, fluconazole).

Uses of Antifungal Drugs

Amphotericin is an antibiotic which either kills fungi (fungicidal) or interferes with their multiplication (fungistatic) according to the dose used and the fungus being treated. It is active against a wide range of fungi and yeasts. Its activity may be increased by giving it along with certain antibacterial drugs and other antifungal drugs (e.g. flucytosine). It is an effective drug which may be given by mouth or infusion into a vein; but it may occasionally produce serious harmful effects. Therefore, expected benefits need to be balanced against the risks of using this drug. See special warnings on the use of intravenous amphotericin preparations in A-Z of Medicines.

As with the treatment of all fungal infections, treatment with amphotericin has to be prolonged – usually about 6–10 weeks, but sometimes as long as 16 weeks.

Clotrimazole is used only in local applications to treat vaginal thrush and ringworm and other forms of infection of the skin.

Econazole is used only in local applications to treat vaginal thrush.

Fluconazole is active by mouth and is used to treat thrush infections of the vagina and mouth and throat. It needs only to be given in a single dose each day. It has less effect than ketoconazole on the breakdown of other drugs by the liver and less effect on the manufacture of steroids.

Flucytosine is effective in the treatment of generalized (systemic) fungal infections caused by certain yeasts, for example thrush. It may be given by mouth and by infusion into a vein. Fungi may become resistant to flucytosine so its use as a single drug should be restricted. However, it increases the effects of amphotericin and the two are often used together for treatment of severe generalized infections.

Griseofulvin is given by mouth for the treatment of fungus infections of the nails and hair. It is only used to treat infections of the skin if applications of antifungal preparations have failed and/or if the disease is widespread over the body. It concentrates in keratin, a protein on the surface layer of the skin which also forms a major component of nails and hair. The drug is deposited in developing keratin-producing cells and makes them resistant to fungal infection; therefore any new growth of hair, nails or skin is free from the infection. The keratin containing the fungus is got rid of through the loss of scales from the skin, and by cutting the nails and the hair. The infected keratin is gradually replaced by uninfected keratin.

As with all antifungal drug treatments, griseofulvin should be continued for weeks or even months.

Itraconazole is used to treat thrush of the vagina and vulva, and fungal skin infections. It can remain in tissues (e.g. the skin) for up to four weeks. It enters infected cells in the base of the skin and as the cells work their way to the surface the infected cells are shed.

Ketoconazole is taken by mouth; it requires acid in the stomach if it is to dissolve and be absorbed into the blood-stream. Therefore, drugs which block acid production (e.g. indigestion mixtures) reduce its absorption. It may, rarely, produce serious harmful effects (e.g. liver damage) and therefore expected benefits from using it should be carefully balanced against such risks. It is useful in treating histoplasmosis and a range of other serious fungal infections. It is better for long-term treatment. In acute infections it is less useful, because its absorption from the intestine is erratic and it is slow to work. It may antagonize the effects of amphotericin. Ketoconazole affects the metabolism of several other drugs.

Miconazole is used in local applications, by mouth and by intravenous infusion. Because of its harmful effects the intravenous use of miconazole should be strictly limited to the treatment of severe, generalized fungal infections that have not responded to other treatments. The main use of miconazole is in local applications for the treatment of vaginal thrush and ringworm and other infections of the skin.

Nystatin is an antibiotic with a similar structure to amphotericin. It both kills fungi (fungicidal) and prevents them multiplying (fungistatic). It is available in ointments, creams, mouth washes, tablets, pastilles and suspensions. It is too toxic to be given by intravenous injection but it is safe by mouth for treating fungal infections of the intestine because it is not absorbed into the blood-stream and is passed out in the motions. It is active against a number of yeasts and fungi but its main use is in treating yeast infections, particularly thrush of the mouth, skin, genitals and anus, and of the oesophagus, stomach and intestine.

There is no evidence that nystatin combined with an antibiotic (e.g. tetracycline) reduces the incidence of thrush of the mouth caused by antibiotics in patients who are prone to develop thrush because of their general condition.

Terbinafine (Lamisil) is used by mouth to treat fungal infections of the skin and nails. There is also a topical preparation.