Antifungal drugs

Key points

There is not a single consistent way to classify antifungal drugs. Furthermore, they are a diverse range of chemical classes. Uses of these agents in veterinary patients are largely driven by the available dose forms rather than activities, toxicities, etc. For our purposes, we will simply consider these drugs based on how they are administered, namely topical and systemic. Where possible, additional organization based on activity against specific categories of organisms (e.g. "effective against dimorphic fungi") within the two administration-based classes.

Antifungal Activity Route(s) Clinical uses and comments
Natamycin dimorphic, filamentous, dermatophytes, yeasts topical - eye (only)
Nystatin yeasts (only) topical (only) Antifungal in Panalog®
Terbinafine dimorphic, dermatophytes, yeasts Topical, systemic Gradually concentrates in dermal tissues with systemic use. Some recommend use for dermatophytes in cat shelters.
Silver sulfadiazine dimorphic, dermatophytes, yeasts topical (only) Antifungal ingredient in Baytril Otic®
Griseofulvin dermatophytes (only) systemic (only) Rarely used because dosing is difficult
Amphotericin dimorphic, filamentous, dermatophytes, yeasts systemic, topical Largely replaced by azoles (especiall triazoles)
Flucytosine dimorphic, dermatophytes, yeasts systemic (only) Clinical use is very rare (side effects) but it does reach CNS
Imidazoles (azole) dimorphic, filamentous, dermatophytes, yeasts topical, ketoconazole still used systemically Endocrine effects preclude systemic use (except ketoconazole)
Triazoles (azole) dimorphic, filamentous, dermatophytes, yeasts systemic Better tolerated (fewer side effects) than imidazoles
Filamentous really means "Aspergillus fumagatus." In-vitro activity may not align with in-vitro activity. (Aspergillosis is very difficult to treat effectively).

Antifungal drug "classes"

Topical Antifungal drugs

Natamycin

Pharmacodynamics

Beneficial actions and effects Adverse effects

Pharmacokinetics

Azole antibiotics - imidazoles (clotrimazole, miconazole, ketoconazole, enilconazole)

Pharmacodynamics

Beneficial actions and effects Adverse effects / limitations

Pharmacokinetics

Nystatin

Pharmacodynamics

Beneficial actions and effects Adverse effects

Pharmacokinetics

Terbinifine

Pharmacodynamics

Beneficial actions and effects Adverse effects

Pharmacokinetics

Silver sulfadiazine

Pharmacodynamics

Beneficial actions and effects Adverse effects

Pharmacokinetics

Systemic antifungal agents

Griseofulvin

Pharmacodynamics

Beneficial actions and effects Adverse effects (actual incidence undocumented)

Pharmacokinetics

Amphotericin B

Pharmacodynamics

Beneficial actions and effects Adverse effects

Pharmacokinetics

Flucytosine

Pharmacodynamics

Beneficial actions and effects Adverse effects

Pharmacokinetics

Azole antifungals - imidazole (ketoconazole) and triazole (itraconazole, fluconazole, voriconazole, posaconazole)

Pharmacodynamics

Beneficial actions and effects Adverse effects

Pharmacokinetics

Terbinafine

Pharmacodynamics

Beneficial actions and effects Adverse effects

Pharmacokinetics