The patient is a 37-year-old African-American man who lives in San Jose, California. He was recently incarcerated near Bakersfield, California and returned to Oakland about 3 months ago. He is currently experiencing one month of severe headache and double vision. He has a temperature of 38.6°C (101.5°F) and the physical exam reveals nuchal rigidity and right-sided sixth cranial nerve palsy. MRI of his brain is normal, and lumbar puncture reveals 330 WBC with 20% eosinophils, protein 75, and glucose 20. HIV test is negative, TB skin test is negative, CSF cryptococcal antigen is negative, and CSF gram stain is negative. Patient receives empiric therapy for bacterial meningitis with vancomycin and ceftriaxone, and is unimproved after 72 hours of treatment. After 3 days a white mold is identified growing from his CSF culture. What medical therapy would be most appropriate now?
Human fungal infections have increased dramatically in incidence and severity in recent years, owing mainly to advances in surgery, cancer treatment, treatment of patients with solid organ and bone marrow transplantation, the HIV epidemic, and increasing use of broad-spectrum antimicrobial therapy in critically ill patients. These changes have resulted in increased numbers of patients at risk for fungal infections.
For many years, amphotericin B was the only efficacious antifungal drug available for systemic use. While highly effective in many serious infections, it is also quite toxic. In the last several decades, pharmacotherapy of fungal disease has been revolutionized by the introduction of the relatively nontoxic azole drugs (both oral and parenteral formulations) and the echinocandins (only available for parenteral administration). The new agents in these classes offer more targeted, less toxic therapy than older agents such as amphotericin B for patients with serious systemic fungal infections. Combination therapy is being reconsidered, and new formulations of old agents are becoming available. Unfortunately, the appearance of azole-resistant and echinocandin-resistant organisms, as well as the rise in the number of patients at risk for mycotic infections, has created new challenges.
The antifungal drugs presently available fall into the following categories: systemic drugs (oral or parenteral) for systemic infections, oral systemic drugs for mucocutaneous infections, and topical drugs for mucocutaneous infections.
SYSTEMIC ANTIFUNGAL DRUGS FOR SYSTEMIC INFECTIONS
Amphotericin A and B are antifungal antibiotics produced by Streptomyces nodosus. Amphotericin A is not in clinical use.
Chemistry & Pharmacokinetics
Amphotericin B is an amphoteric polyene macrolide (polyene = containing many double bonds; macrolide = containing a large lactone ring of 12 or more atoms). It is nearly insoluble in water and is therefore prepared as a colloidal suspension of amphotericin B and sodium deoxycholate for intravenous injection. Several formulations have been developed in which amphotericin B is packaged in a lipid-associated delivery system (Table 48–1 and Box: Lipid Formulation of Amphotericin B).