Antifungal Drugs

Abstract

There are a number of antifungal drugs authorised for use in animals, the majority being members of the polyene or azole classes. Of these, only two are permitted for use in food animals, at least in the European Union, natamycin and enilconazole. Griseofulvin is a cyclohexenone derivative which has been used in companion and food animal medicine. However, it has been shown to be teratogenic and its use is now restricted to companion animals because of consumer safety concerns when used in food animals. Amphotericin B is a polyene antifungal agent whose use in human medicine is associated with nephrotoxicity which in some circumstances may be severe and may lead to renal failure. In contrast, another member of the group, natamycin, has low toxicity in humans and in animals. The azoles include the imidazoles and the traizoles. These drugs produce their desired pharmacodynamic effects through the inhibition of fungal steroidogenesis. However, they may also produce similar inhibitory effects on mammalian steroidogenesis. This inhibition may have beneficial effects, for example in the therapeutic treatment of steroid dependent cancers such as prostate. However, there may also be adverse effects including those on the reproductive system and on the outcome of gestation. Several members of the group including itraconazole, fluconazole and ketoconazole are also hepatotoxic. Many of the effects seen with these compounds only occur at high therapeutic doses in humans or at high doses in animal studies and so they are unlikely to occur as a result of infrequent occupational exposure to relatively low doses. Their restricted use in food animals reduces concerns over possible adverse effects in consumers who might otherwise be exposed to residues in food of animal origin.