Antifungal drugs are a type of drugs which are used in treatment of different fungal infections. Amongst such preparations two large groups can be distinguished, systemic and locally used anti-fungal drugs. The difference in them consists in the type of administration used. Systemic drugs are administered orally and parenterally and local drugs are intended only for external administration.
Antifungal drugs work by using the difference in the structure of human cells and fungal cells, thus avoiding any dangerous effects on the human host. Fungal infections most commonly affect skin or mucous membranes, causing local or superficial mycosises, however in immune deficiency states internal organs may be affected causing systemic or deep mycosis. Mycosises are most commonly caused by fungal organisms called dermatophytes, which may affect skin, hair and nails.
Another classification of antifungal drugs by chemical structure, spectrum of activity, pharmacokinetics, tolerability and etc. exists:
- Polyene antibiotics: nystatin, levorin, natamycin, amphotericin B - The drugs belonging to the above mentioned group are mostly of bacterial origin. They work by increasing the permeability of the fungal cellular membranes, thus expressing fungicidal effects. One of the preparations in the group should be noted exceptionally - Amphotericin B, the preparation is active against most organisms which are responsible for systemic mycoses, due to a low level of the drugs absorbability for different mycoses it should be administered differently. For example in systemic mycosis it is used parenterally, and expresses a large number of side effects including: chills, fever, CNS disturbance and etc. In treatment of external mycoses it is applied in cream form to the affected area. In cases of intestinal candydiasis it is administered orally, and due to a very low level of absorption it has no systemic effects.
- Imidazole derivates: clotrimazole, ketoconazole, miconazole, oxiconazole, bifonazole - This type of antifungal drugs work by inhibiting ergosterol synthesis. Ergosterol is a key component of the fungal cellular membrane, inhibition of its synthesis leads to fungistatic or fungicidal effect. Fungistatic effect may be explained by the inability of the fungal cell to grow and develop normally, on the over hand fungicidal effect may develop only during the use of increased dosages of imidazoles. The preparation of the class affect a broad-spectrum of fungal cultures. Due to specific properties of the drugs, meaning poor systemic tolerability and absorption, most of the drugs are used only in treatment of local or external infections and rarely systemically for short-term infusions.
- Triazole: fluconazole, itraconazole: A newly developed branch of antifungal drugs which takes its origin in Imidazoles. The mode of action of the drugs does not differ from the Imidazoles, however the drugs in the group have proven to be more effective in safe during treatment.
- Allylamines: terbinafine, naftifine: Group of synthetic antifungal drugs, with high lipophilicity which are used locally and systemically.
- Drugs belonging to other chemical groups: griseofulvin, flucytosine, chloronitrophenol, potassium iodide.