Amphotericin B is one of the most effective antifungal drugs ever developed, but its side effects are so well known that clinicians have nicknamed it “ampho-terrible.” The drug’s toxicity profile is dominated by kidney damage, which can occur in a substantial fraction of patients, but it also causes acute infusion reactions, electrolyte derangements, anemia, and occasionally liver or cardiac problems. How severe these side effects become depends on which formulation you receive, how fast it is infused, what other medications you are taking, and how aggressively your medical team works to prevent complications.
Why the Drug Causes Harm in the First Place
Amphotericin B works by binding to sterols in fungal cell membranes, primarily ergosterol. That binding disrupts the membrane and kills the fungus. The problem is that human cell membranes contain cholesterol, which is structurally similar enough to ergosterol that the drug binds to it too. Research has shown that the drug’s C2′ hydroxyl group plays a key role in binding cholesterol in human cells, which likely accounts for much of the toxicity people experience.1PubMed Central. C2′-OH of amphotericin B plays an important role in binding the primary sterol of human cells but not yeast cells When the drug interacts with cholesterol in kidney tubule cells, heart muscle cells, or red blood cells, it creates pores in those membranes. That pore formation is the root cause of most organ-specific side effects.
Infusion-Related Reactions
The most immediately noticeable side effects happen during or shortly after each infusion. Patients commonly experience fever, chills, rigors (intense shaking), nausea, vomiting, and headache. These reactions can look alarmingly similar to sepsis, and the resemblance is not coincidental. Amphotericin B triggers immune cells to release a cascade of inflammatory molecules, including TNF-alpha, interleukin-6, interleukin-1 beta, and several other cytokines and chemokines.2Journal of Biological Chemistry. The Antifungal Drug Amphotericin B Promotes Inflammatory Cytokine Release by a Toll-like Receptor- and CD14-dependent Mechanism This happens through the same toll-like receptor pathway that the body uses to respond to bacterial infections, which is why the symptoms mimic a genuine infection. The interleukin-1 beta release, specifically, is dose-related, meaning higher drug concentrations trigger a bigger inflammatory response.3PubMed Central. Pharmacologic modulation of interleukin-1 expression by amphotericin B-stimulated human mononuclear cells
These reactions tend to be worst with the first few doses and often become milder over time as the body develops some tolerance. Premedication with acetaminophen, diphenhydramine, or hydrocortisone before each infusion can significantly reduce the likelihood of these reactions. Real-world data from oncology and hematology centers showed a statistically significant protective effect when premedication was given starting from the very first dose.4PubMed Central. Acute Infusion-Related Side Effects of Amphotericin B Lipid Complex (ABLC) in Oncohematological Patients: Real-World Data from Brazilian Reference Centers Even so, some patients still experience breakthrough reactions, and severe rigors occasionally require meperidine to control.
Kidney Damage
Nephrotoxicity is the side effect that most limits amphotericin B therapy. The drug damages the kidneys in two main ways. First, it constricts blood vessels supplying the kidneys, reducing blood flow. Second, and more directly, it forms pores in the membranes of kidney tubule cells. Sodium rushes through those pores, activating stress-signaling pathways inside the cells and raising intracellular calcium to toxic levels, which ultimately injures or kills the cells.5PubMed Central. Amphotericin B-induced renal tubular cell injury is mediated by Na+ Influx through ion-permeable pores and subsequent activation of mitogen-activated protein kinases and elevation of intracellular Ca2+ concentration
How often kidney injury occurs depends heavily on the formulation and the patient’s risk profile. For conventional amphotericin B deoxycholate, one large epidemiological study identified five categorical risk factors for moderate-to-severe kidney damage: a mean daily dose of 35 mg or more, male sex, body weight of 90 kg or above, pre-existing chronic kidney disease, and concurrent use of the drugs amikacin or cyclosporine. Among patients with none of these risk factors, the rate of significant nephrotoxicity was around 4%. With one risk factor it rose to 8%, with two it reached 18%, and with three or more it hit 29%.6PubMed. The epidemiology of nephrotoxicity associated with conventional amphotericin B therapy More severe injury tends to occur when patients are volume-depleted (from diuretics, for instance) or when they are simultaneously receiving other nephrotoxic drugs.7PubMed Central. Liposomal amphotericin B and renal safety: review of the evidence and clinical considerations
Can the Kidneys Recover?
Whether kidney function bounces back after amphotericin B-induced injury is a question patients understandably worry about. The news is mixed. In a study tracking patients who developed acute kidney injury from liposomal amphotericin B, about a third achieved full renal recovery, with creatinine returning to baseline in an average of roughly 10 days after the injury began. About half showed at least partial recovery. But the other half had creatinine levels that never came back to within 25% of their pre-treatment value by the end of follow-up.8PubMed Central. Renal Recovery following Liposomal Amphotericin B-Induced Nephrotoxicity
That said, a separate study of outpatient liposomal amphotericin B therapy found that 90% of patients achieved at least partial renal recovery within 30 days of stopping the drug, and most side effects were managed without long-term consequences.9PubMed Central. Experience with Liposomal Amphotericin B in Outpatient Parenteral Antimicrobial Therapy The difference between these findings likely reflects different patient populations and how sick they were to begin with. The overall picture is that kidney damage from amphotericin B is often reversible if caught early and managed properly, but in a meaningful minority of patients, some degree of lasting impairment persists.
Electrolyte Problems
The same membrane pores that damage kidney tubule cells also cause the kidneys to lose potassium and magnesium into the urine at abnormally high rates. Hypokalemia (low potassium) and hypomagnesemia (low magnesium) are among the most common side effects of amphotericin B therapy. In one outpatient study of liposomal amphotericin B, low potassium occurred in about 62% of patients.10PubMed Central. Experience with Liposomal Amphotericin B in Outpatient Parenteral Antimicrobial Therapy This is clinically important because severe hypokalemia can cause dangerous heart rhythm disturbances and muscle weakness.
Managing these losses requires aggressive supplementation with potassium and magnesium throughout the course of treatment. The potassium-sparing diuretic amiloride has been studied as a way to reduce renal potassium wasting. In a controlled trial, patients receiving amiloride alongside amphotericin B maintained significantly higher potassium levels and needed substantially less potassium supplementation. Amiloride may also reduce magnesium loss.11PubMed. Amiloride for the prevention of amphotericin B-induced hypokalemia and hypomagnesemia Current recommendations call for checking electrolytes, along with kidney and liver function, at least weekly during therapy, with daily kidney function monitoring in some settings.12Journal of Antimicrobial Chemotherapy. Liposomal amphotericin B and renal safety: review of the evidence and clinical considerations
Anemia
Amphotericin B frequently causes anemia that develops gradually over the course of treatment. The red blood cells that are produced look normal in size and color under a microscope, but the body simply does not make enough of them. Early research suggested this might be due to direct bone marrow suppression, but studies found something more specific: the drug appears to blunt the body’s production of erythropoietin, the hormone that signals the bone marrow to ramp up red blood cell manufacturing.13PubMed Central. Erythropoietin concentration in amphotericin B-induced anemia In patients with significant anemia, researchers could not detect the expected rise in erythropoietin levels that should accompany low red blood cell counts.14PubMed. Amphotericin B blunts erythropoietin response to anemia The anemia is generally reversible after stopping the drug, as erythropoietin production resumes. In the meantime, some patients need blood transfusions during prolonged courses of therapy.
Lipid Formulations and How They Change the Risk
Much of the effort to tame amphotericin B’s toxicity over the past few decades has focused on reformulating it. The original preparation, amphotericin B deoxycholate, is the version most associated with severe side effects. Three lipid-based formulations now exist: liposomal amphotericin B (AmBisome), amphotericin B lipid complex (Abelcet), and amphotericin B colloidal dispersion. By packaging the drug in lipid carriers, these formulations deliver the active agent to fungal cells while reducing how much free drug interacts with healthy tissue.
The kidney-sparing effect is where lipid formulations have the clearest advantage. A Cochrane systematic review found that liposomal amphotericin B cut the risk of significant creatinine elevation roughly in half compared to conventional amphotericin B.15PubMed Central. Amphotericin B deoxycholate versus liposomal amphotericin B: effects on kidney function Across various meta-analyses and real-world studies, nephrotoxicity rates with lipid formulations range from roughly 9% to 25%, compared with 12% to 50% for the conventional drug. Severe nephrotoxicity rates are even more divergent: about 11.5% with conventional amphotericin B, 7.2% with amphotericin B lipid complex, and just 2.4% with the liposomal version.16Journal of Antimicrobial Chemotherapy. Liposomal amphotericin B and renal safety: review of the evidence and clinical considerations A trial sequential analysis across 10 randomized studies confirmed this lower nephrotoxicity with statistical confidence.17Archives of Medical Science. Nephrotoxicity of three formulations of amphotericin B: trial sequential analysis
Despite these advantages, lipid formulations are not side-effect-free. They can still cause infusion reactions, electrolyte wasting, and anemia. They are also dramatically more expensive than conventional amphotericin B, which remains a major consideration in low- and middle-income countries where invasive fungal infections are common and drug budgets are tight.
Strategies to Reduce Kidney Damage
When conventional amphotericin B must be used, several strategies can soften the blow to the kidneys. The most established is saline loading before each infusion. The idea is straightforward: giving intravenous normal saline expands blood volume and counteracts the drug-induced constriction of kidney blood vessels. A randomized, double-blinded study found that patients who received one liter of normal saline before amphotericin B maintained stable kidney function over 10 weeks, while those who received dextrose instead had a significant rise in creatinine.18PubMed. Effect of salt supplementation on amphotericin B nephrotoxicity Current practice typically recommends 500 to 1,000 mL of normal saline before each dose, with careful electrolyte supplementation alongside.19PubMed. Effects of hydration with salt repletion on renal toxicity of conventional amphotericin B empirical therapy: a prospective study in patients with hematological malignancies
Research on dosing specifics suggests the amount of saline should scale with the amphotericin B dose. For doses up to 50 mg per day, 500 mL may suffice, but for higher daily doses, at least 1,000 mL is preferred, aiming for a ratio of at least 10 mL of saline per milligram of drug.20PubMed Central. The dose of the normal saline pre-infusion and other risk factors for amphotericin B deoxycholate-associated acute kidney injury This may sound like a small detail, but for a patient receiving 75 mg daily, the difference between 500 mL and 1,000 mL of pre-infusion saline could meaningfully affect whether they develop kidney injury.
Slowing Down the Infusion
Another approach is simply running the infusion over a longer period. Standard practice typically delivers amphotericin B over four to six hours, but continuous 24-hour infusion has been studied as a way to reduce peak drug concentrations and give the kidneys a gentler exposure. In one study comparing continuous infusion to the standard four-hour infusion in high-risk hematology patients, kidney impairment occurred in only 10% of the continuous-infusion group versus 45% in the four-hour group. An infusion rate below 0.08 mg/kg per hour was associated with a significant reduction in renal impairment, and the continuous-infusion group also had better survival.21Journal of Antimicrobial Chemotherapy. Continuous and 4 h infusion of amphotericin B: a comparative study involving high-risk haematology patients
A meta-analysis of the available trials found a trend toward lower nephrotoxicity with continuous infusion, though the result did not quite reach conventional statistical significance.22PubMed Central. Continuous versus Conventional Infusion of Amphotericin B Deoxycholate: A Meta-Analysis Overall, continuous infusion is considered a feasible and safer alternative, particularly for patients who must receive conventional amphotericin B and are at high risk for kidney problems.23PubMed Central. Amphotericin B used as a continuous infusion is safer
Less Common but Serious Side Effects
Beyond the kidney, electrolytes, blood, and infusion reactions, amphotericin B occasionally affects other organs. Liver toxicity is uncommon but documented. In one reported case, a patient receiving high-dose amphotericin B developed asymptomatic elevations in liver enzymes and bilirubin. The abnormalities resolved when the drug was stopped, returned when it was restarted at a lower dose, and resolved again on discontinuation, strongly implicating the drug as the cause.24PubMed Central. Reversible hepatotoxicity related to amphotericin B Interestingly, in one pediatric study, liver enzyme elevations were actually more common with liposomal amphotericin B than with the conventional formulation, occurring in about 83% versus 56% of children. The study also found that infusion-related reactions were uncommon in infants younger than 90 days, and kidney toxicity rates were similar between formulations in this age group.25PubMed Central. Adverse effects of amphotericin B in children; a retrospective comparison of conventional and liposomal formulations
Cardiac toxicity is rare. A case report described a 9-month-old infant who developed episodes of second-degree heart block during liposomal amphotericin B therapy. The bradycardia resolved after the drug was stopped, on a timeline consistent with the drug’s half-life. The mechanism is not fully understood but may involve disruption of cardiac muscle cell membrane depolarization, consistent with the drug’s general tendency to disrupt cell membranes.26PubMed Central. Atrioventricular block related to liposomal amphotericin B Because of this risk, rapid intravenous pushes of amphotericin B are avoided, as they can cause acute electrolyte shifts that compound any direct cardiac effects.
A Dangerous Drug Interaction Worth Knowing About
One of the most dramatic and historically important amphotericin B interactions involves leukocyte transfusions, a therapy sometimes used in severely immune-compromised patients with life-threatening infections. A review spanning more than six years at the National Institutes of Health found that when amphotericin B was given during leukocyte transfusion courses, 64% of those courses were complicated by acute respiratory deterioration, compared to only 6% of courses without amphotericin B. Patients developed sudden difficulty breathing, low blood oxygen, and lung infiltrates visible on chest X-rays. The reaction contributed to death in five patients.27PubMed. Lethal pulmonary reactions associated with the combined use of amphotericin B and leukocyte transfusions Although leukocyte transfusions are now relatively uncommon, this remains a critical interaction to be aware of in the rare situations where both therapies are considered.
More frequently encountered drug interactions center on other nephrotoxic medications. Receiving amphotericin B alongside aminoglycoside antibiotics like amikacin, or immunosuppressants like cyclosporine, substantially raises the risk of kidney damage, as noted in the epidemiological risk-factor analysis mentioned earlier.28PubMed. The epidemiology of nephrotoxicity associated with conventional amphotericin B therapy Diuretics pose a double threat: they deplete volume (worsening renal blood flow) and can exacerbate the potassium and magnesium losses that amphotericin B already causes.29PubMed Central. Liposomal amphotericin B and renal safety: review of the evidence and clinical considerations
Why Clinicians Still Use It
Given all of this, you might wonder why anyone would prescribe amphotericin B at all. The answer is that for certain invasive fungal infections, no other drug matches its combination of broad antifungal coverage and low resistance rates. Fungi have had decades to develop resistance to newer antifungal classes, but resistance to amphotericin B remains remarkably rare. For patients with mucormycosis, severe cryptococcal meningitis, or disseminated histoplasmosis, amphotericin B is often the first-line treatment because the alternatives are either less effective, not available, or the fungus is resistant to them. The development of lipid formulations has made it possible to deliver effective therapy while substantially lowering the risk of the worst side effects, turning what was once a nearly intolerable drug into something that can be managed with proper monitoring and supportive care.