0071483446.pdf

Antifungal Drugs (Antimycotic Drugs)

These drugs are used to treat two types of fungal infections

1.Superficial fungal infections of skin or mucous membrane.

2.Systemic fungal infections of the lung or central nervous system.

The conditions may be mild such as tinea pedis (ahtlete’s foot), or severe as

in pulmonary conditions or meningitis.

Fungi, such as Candidaspp. (yeast), are normal flora of mouth, skin, intes-

tine, and vagina. Candidiasis might be an opportunistic infection when the

defense mechanisms are impaired. Antibiotics, oral contraceptives, and immuno-

suppressives may alter the body’s defense mechanisms. Infections can be mild

(vaginal yeast infection) or severe (systemic fungal infection).

There are four groups of anti-fungal medications. They are:

1.Polyenes, including amphotericin B and nystatin.

2.Imidazoles which include ketoconazole, miconazole, and clotrimazole.

3.Antimetabolic antifungal flucytosine.

4.Antiprotozoal agents.

Polyenes such as amphotericin B are the drug of choice for treating severe

systemic infections. It is effective against numerous diseases including histo-

plasmosis, cryptococcosis, coccidioidomycosis, aspergillosis, blastomycosis, and

candidiasis (system infection), however, it is very toxic. It is not absorbed from

the GI tract so it cannot be given by mouth.

It is usually prescribed as Amphotericin B (Fungizone). A test dose is given

IV: 0.25–1.0 mg in 20 mL of D5W infused over 20–30 min; IV: 0.25–1.0

mg/kg/d in D5W or 1.5 mg/kg qod; max; 1.5 mg/kg/d. The drug is pregnancy

category: B; PB: 95%; t^1 ⁄ 2 : 24 h.

Side effects and adverse reactions include flushing, fever, chills, nausea,

vomiting, hypotension, paresthesias, and thrombophlebitis. It is highly toxic,

causesnephrotoxicity and electrolyte imbalance, especially hypokalemia (low

potassium) and hypomagnesemia (low serum magnesium). Urinary output,

BUN, and serum creatinine levels should be closely monitored.

Nystatin (Mycostatin) can be given orally or topically to treat candidal infec-

tion. It is available in suspensions, cream, ointment, and vaginal tablets. It is

poorly absorbed via the GI tract but the oral tablet form is used for intestinal

(^246) CHAPTER 13 Antimicrobials—Fighting Infection