Polyenes
Polyenes are a group of antifungal antibiotics that combine with the ergosterol in the
plasma membrane of fungi. This causes the plasma membrane to become extremely
permeable, ultimately resulting in the death of the fungi. A commonly used poly-
ene is amphotericin B, which is used to treat histoplasmosis, coccidioidomycosis,
and blastomycosis. However, amphotericin B is toxic to kidneys. Enclosing ampho-
tericin B in liposomes when administering the drug reduces its toxicity.
Imidazoles
Imidazoles interfere with fungal ergosterol synthesis. Commonly used imida-
zoles are:
- Clotrimazole is used to treat cutaneous mycoses. Two example are athlete’s
foot and vaginal yeast infections. - Miconazoleis similar to clotrimazole. Both drugs are used topically and
sold without a prescription.
Triazoles
Triazoles are similar to imidazoles, but are less toxic than other antifungals.
Griseofulvin
Griseofulvin is an antibiotic used to treat dermatophytic fungal infections of the
hair and nails. This includes tinea capitis. Griseofulvin is taken orally and enters
the keratin of skin, hair, and nails. Its purpose is to interfere with fungal mitosis,
inhibiting reproduction.
Tolnaftate
Tolnaftateis a topical treatment for athlete’s foot. Its mechanism for action is
unknown.
ANTIVIRAL DRUGS
Antiviral drugs interfere with the replication of viruses. Commonly used antivi-
ral drugs follow.
CHAPTER 16 Antimicrobial Drugs^243