Anti-Fungal Agents

Fungal infections (mycoses), though not as frequent as bacterial or viral infections, have nonetheless been increasing in incidence in the human population over the last 15 years or so, largely as a consequence of increased numbers of cancer and immunocompromised patients, who are at greater risk owing to weakened immune systems and the chronic nature of the diseases. In addition, a number of fungal infections can be difficult to treat (oft referred to as ‘stubborn’), even when the offending organism is identified and appropriate therapy is applied. On the other hand, like bacteria, fungi have unique characteristics, distinct from their mammalian hosts, allowing for selective targeting of therapeutic drugs. Fungi are, however, much more complex organisms in comparison to bacteria, are in fact eukaryotic and often grow fairly slowly. Consequently, only a few drugs are aimed at interfering with cell division and have limited use. Most antifungal drugs are targeted to the cell membrane.

Major fungal infections

The number of different kinds of fungi out there is vast, and, of course, some of them are pleasant to eat. Only a small subset is capable of infecting humans. The following is a very general breakdown of types of fungal infections that occur based on site of infection:

Cutaneous = skin, hair and nails Most common

eg. ‘Athlete’s foot’, Ringworm, and Tinea cruris

Mucocutaneous = moist skin and mucous membranes, Common

such as GI, perianal and vulvovaginal areas

eg. Candida albicans

Pulmonary/Systemic Less frequent

eg. Invasive Aspergillus, cryptococcal meningitis, pulmonary histoplasmosis; also, systemic candidiasis

Systemic fungal infections are more serious as they are usually more difficult to diagnose, are chronic in nature, and, in some cases, can become life-threatening. They occur more frequently in individuals with compromised immune systems (AIDS patients; transplant patients; cancer patients). Prophylactic treatment is sometimes indicated in AIDS patients and bone marrow transplant patients, but risk of developing resistance is high. Life-threatening infections require the use of more potent but much more toxic antifungals.

Superficial fungal infections are almost always caused by dermatophytes or yeasts. In some instances, they can be rather tenacious, requiring very long treatments, sometimes with both oral and topical drugs.

Category: Pharmacology Notes