Nursing care
Antifungals: what to check before you give it
Written and reviewed by Dana Whitfield, RN, MSN · 5 min read · Updated September 2026
Short answer
Antifungals require nursing focus on renal function, hepatic function and drug interactions, because the two mainstay classes carry the most consequential toxicities in nursing practice: amphotericin B causes a severe infusion reaction nicknamed shake and bake and is significantly nephrotoxic, while azoles like fluconazole inhibit liver enzymes and interact with many common drugs.
Mechanism, simply
Fungal cell membranes depend on ergosterol the way human cell membranes depend on cholesterol. Amphotericin B binds ergosterol directly and punches holes in the fungal membrane, killing the organism, but ergosterol is similar enough to cholesterol that human cell membranes, particularly in the kidney, get damaged too. That shared vulnerability is the root of its nephrotoxicity.
Azole antifungals such as fluconazole work differently: they block an enzyme fungi need to synthesise ergosterol in the first place, starving the membrane of its structural component rather than attacking it directly. That enzyme, CYP450, is shared with the human liver's drug-metabolising pathway, which is why azoles are such prolific interaction drugs rather than direct organ toxins in the way amphotericin B is.
Indications you will see on the ward
Fluconazole covers common candida infections: oral and oesophageal thrush, vaginal candidiasis, and candidemia in a stable patient. It is also used as prophylaxis in some immunocompromised populations. Amphotericin B is reserved for severe, invasive, or systemic fungal infections, including disseminated candidiasis, aspergillosis, and cryptococcal meningitis, typically in patients who are critically unwell or have failed less toxic options.
The contrast matters clinically: amphotericin B is not a first-line choice for a routine yeast infection. Seeing it ordered should prompt you to expect a sicker patient, closer monitoring, and a conversation with the team about renal protection strategies before the first dose runs.
Assessment before administration
Before any dose of amphotericin B, obtain a baseline renal panel, including creatinine and electrolytes, particularly potassium and magnesium, since the drug also causes renal wasting of both. Vital signs at baseline are essential, because the infusion reaction typically appears within the first hour and includes fever, rigors, chills, and sometimes hypotension.
For azoles, review baseline liver function and take a full medication history before the first dose, since interactions are the dominant risk rather than an acute infusion reaction. For any antifungal, confirm there is no known hypersensitivity and check for pregnancy status where relevant, as some azoles carry teratogenicity concerns.
Toxicity and the antidote
Amphotericin B earned the nickname shake and bake because the infusion reaction genuinely looks like that: violent rigors and spiking fever during or shortly after the infusion. Premedication with an antipyretic, an antihistamine, and sometimes hydrocortisone is standard practice to blunt the reaction, and slowing the infusion rate can help if it occurs.
There is no specific antidote for amphotericin B toxicity; management is supportive and preventive. Nephrotoxicity is managed by adequate pre-hydration with normal saline before infusion, monitoring renal function and electrolytes throughout the course, and using a lipid formulation of the drug where available, since lipid formulations are considerably less nephrotoxic than the conventional deoxycholate form.
Interactions that matter
Fluconazole and other azoles inhibit CYP450 enzymes, raising serum levels of drugs metabolised by that pathway. Warfarin is a key example: azoles can potentiate its anticoagulant effect and raise INR unpredictably, so a patient stable on warfarin who starts fluconazole needs closer INR monitoring. Statins metabolised through the same pathway carry an increased risk of myopathy when combined with azoles.
Amphotericin B compounds nephrotoxicity when given alongside other nephrotoxic agents, including aminoglycosides, NSAIDs, and certain diuretics, so a full medication reconciliation before starting it is not optional. Its potassium-wasting effect also raises the risk of digoxin toxicity in a patient taking both, since hypokalaemia sensitises the myocardium to digoxin's effects.
What the patient must be told
A patient starting amphotericin B should be warned in advance that fever and shaking are an expected part of the infusion for many people, not a sign that something has gone wrong, so they are not alarmed when it happens. They should also understand why frequent blood tests for kidney function are part of the plan, since unexplained repeated blood draws are a common source of patient anxiety.
A patient starting fluconazole or another azole should be asked to disclose every medication they take, including over-the-counter and herbal products, because the interaction risk is broad and not always obvious to the patient. Anyone on warfarin should be told to watch for unusual bruising or bleeding and to have their INR checked as advised, and anyone on a statin should report new muscle pain.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our pharmacology practice questions are the closest set to what this page covers.
One question from the pharmacology set
A client with heart failure is started on furosemide 40 mg PO daily. Which findings should the nurse report to the provider before administering the next dose? Select all that apply.
Rationale
Furosemide is a loop diuretic, so the two things you are watching are potassium and kidney function. A potassium of 2.9 mEq/L is below the 3.5–5.0 reference range and puts the client at risk for dysrhythmia — hold and report. Muscle cramps with palpitations are the clinical face of that same hypokalemia, so they are reported together, not separately. A creatinine that doubles signals the diuresis has outrun renal perfusion. A blood pressure of 132/78 and a 1 kg loss are the expected response to the drug working, not reasons to hold it.
Answer: A, D, E
Common questions
Why is amphotericin B called shake and bake?
The name describes the classic infusion reaction: rigors, or shaking chills, combined with a spiking fever, both of which typically appear during or soon after the infusion starts. It reflects a direct reaction to the drug rather than an allergic hypersensitivity in most cases.
What labs should be monitored during amphotericin B therapy?
Renal function, including creatinine and BUN, along with potassium and magnesium, should be checked regularly throughout the course, since the drug causes both nephrotoxicity and renal electrolyte wasting. Baseline values before the first dose give a point of comparison.
Can fluconazole be given with warfarin?
It can, but with caution and closer INR monitoring, because fluconazole inhibits the liver enzymes that metabolise warfarin and can raise its anticoagulant effect. A dose adjustment to warfarin may be needed while the azole is on board.
Does pre-hydration actually reduce amphotericin B nephrotoxicity?
Yes, giving normal saline before the infusion is a standard preventive measure and is supported by consistent clinical practice, though it does not eliminate the risk entirely. It is used alongside careful monitoring rather than as a substitute for it.
Is the lipid formulation of amphotericin B always preferred?
It is preferred where cost and availability allow, because it is considerably less nephrotoxic than the conventional formulation. Choice between formulations depends on the clinical setting, the severity of infection, and institutional protocols, so it varies by facility.
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