McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 1 1  Antifungal agents

TABLE 11.1

DRUGS IN FOCUS Systemic antifungals continued

Drug name

Dosage/route

Usual indications

griseofulvin (Grisovin)

Tinea corporis, tinea cruris and tinea capitis: Adult: 500 mg/day Tinea pedis and tinea unguium: Adult: 500 mg/day Paediatric: 10 mg/kg/day in divided doses 500,000–1,000,000 units t.d.s. PO; continue for 48 hours after resolution to prevent relapse; also used topically

Treatment of variety of ringworm or tinea infections caused by susceptible Trichophyton species, including tinea corporis, tinea pedis, tinea cruris, tinea barbae, tinea capitis and tinea unguium Treatment of candidiasis (oral form); treatment of local candidiasis, vaginal candidiasis, and cutaneous and mucocutaneous infections caused by Candida species

nystatin (Kenacomb, Mycostatin, Nilstat)

Cilia with microtubules

Golgi apparatus

Peroxisomes

Cell membrane

Lysosomes

Nucleus: Nuclear membrane Nuclear pore Nucleolus

Topical antifungals

Centrioles

Microtubules

Polyribosomes

Mitochondria

Smooth endoplasmic reticulum

Rough endoplasmic reticulum

FIGURE 11.1  Sites of action of antifungal agents. Both systemic and topical antifungals alter fungal cell permeability, leading to prevention of replication and cell death.

Systemic antifungals

Ketoconazole, fluconazole and itraconazole work by blocking the activity of a sterol in the fungal wall. In addition, they may block the activity of human steroids, including testosterone and cortisol (see usual indications in Table 11.1). Posaconazole is one of the newest antifungals (see Table 11.1 for uses). This drug and voriconazole inhibit the synthesis of ergosterol, which leads to the inability of the fungus to form a cell wall, which results in cell death. Terbinafine is a similar drug that blocks the for- mation of ergosterol. It inhibits a cytochrome P450 2D6 (CYP2D6) enzyme system, so it may be a better choice

for people who need to take drugs metabolised by the cytochrome P450 (CYP450) system. It is available in a sprinkle formulation for children. Pharmacokinetics Ketoconazole, itraconazole, posaconazole and terbi- nafine are administered orally. Ketoconazole is also available as a shampoo and a cream. Fluconazole and voriconazole are available in oral and intravenous (IV) preparations, making it possible to start the drug intravenously for a serious infection and