Amphotericin B

Nicknamed "amphoterrible" by clinicians for good reason — this drug can save a life from a devastating fungal infection while simultaneously destroying the kidneys. Knowing when and how to protect the patient is the NCLEX edge.

Amphotericin B is a polyene antifungal reserved for serious, life-threatening systemic fungal infections (aspergillosis, cryptococcal meningitis, mucormycosis, disseminated candidiasis) when azole antifungals are insufficient or contraindicated. It works by binding to ergosterol in the fungal cell membrane, creating pores that cause leakage of intracellular contents and cell death. Human cells contain cholesterol instead of ergosterol, which provides selectivity — but not enough. The drug is profoundly nephrotoxic; up to 80% of patients develop some degree of renal impairment. Infusion-related reactions (fever, rigors, chills, hypotension) are so common they're expected — premedication with acetaminophen, diphenhydramine, and sometimes meperidine for rigors is standard. Normal saline boluses (500 mL–1 L) before and after infusion help protect the kidneys through volume loading. BUN, creatinine, and electrolytes — especially potassium and magnesium — must be monitored before each dose because amphotericin B causes renal wasting of both. Liposomal formulations (AmBisome) reduce nephrotoxicity but do not eliminate it.

Key Distinctions

Don't confuse amphotericin B with azole antifungals — azoles inhibit ergosterol synthesis, while amphotericin B binds existing ergosterol directly, making it fungicidal rather than fungistatic. Students often attribute infusion reactions to allergy and think to stop the drug; these reactions are expected and managed with premedication, not discontinuation. Hypokalemia from amphotericin B is renal wasting, not inadequate intake — replacement is the intervention.

Clinical Pearl

"Amphoterrible" earns its name through the kidneys: if creatinine is climbing, you report it before the next dose. Hydrate before, hydrate after, and check K+ every time.