No—azithromycin and digoxin should not be combined without careful medical supervision and dose adjustment. Azithromycin inhibits P-glycoprotein, a transporter protein that normally excretes digoxin from the body. This interaction can raise digoxin blood levels by 20–50%, pushing patients toward digoxin toxicity, which causes irregular heartbeat, nausea, and potentially fatal arrhythmias. The FDA classifies this as a moderate-severity interaction requiring monitoring and possible digoxin dose reduction.
The FDA drug labeling databases identify this interaction as moderate in severity. Digoxin's FDA-approved label specifically warns that certain macrolide antibiotics—including azithromycin—can increase serum digoxin concentrations. The mechanism is documented as P-glycoprotein inhibition. Digoxin has a narrow therapeutic window: the difference between an effective dose and a toxic dose is small (therapeutic range typically 0.5–2.0 ng/mL). When azithromycin blocks the protein that clears digoxin from the body, levels can climb into the toxic range within 3–7 days of starting the antibiotic.
The FDA does not explicitly contraindicate the combination, but the labeling requires practitioners to monitor serum digoxin concentrations and watch for signs of toxicity. This reflects a "use with caution" stance: the combination is permissible in specific clinical scenarios, but only with active management.
Digoxin is a cardiac glycoside—a drug that strengthens heart contractions by blocking the sodium-potassium pump on cardiac myocytes. It is a substrate for P-glycoprotein (also called MDR1 or ABCB1), an efflux transporter located in the intestinal epithelium, kidney tubules, and hepatocytes. P-glycoprotein actively pumps digoxin out of cells back into the bloodstream and urine, which is the primary mechanism by which the body clears digoxin.
Azithromycin, a macrolide antibiotic, is a potent inhibitor of P-glycoprotein. When azithromycin is present, it competes for binding sites on P-glycoprotein or reduces the transporter's expression, slowing digoxin elimination. The result is bioaccumulation: digoxin blood concentrations rise because the body cannot excrete it efficiently. Published pharmacokinetic studies document that azithromycin can increase digoxin AUC (area under the concentration curve) by 20–50%, depending on dose, duration of azithromycin therapy, and individual variability in P-glycoprotein function.
This is distinct from a simple drug-drug metabolism interaction. Both digoxin and azithromycin are substrates for CYP3A4, but the primary interaction is via P-glycoprotein inhibition, not cytochrome P450 competition. This means the interaction is primarily renal and biliary in nature, making it especially pronounced in patients with reduced kidney function.
Older adults are the highest-risk population. Digoxin is still commonly prescribed for heart failure and atrial fibrillation, particularly in patients over age 65. Age-related decline in renal function (even with normal creatinine on screening) reduces digoxin clearance by 30–50%. When azithromycin is added, the cumulative effect on elimination can be dramatic. A 70-year-old on maintenance digoxin is at substantially higher risk than a 40-year-old on the same dose.
Patients with renal impairment (eGFR <60 mL/min/1.73m²) face the highest risk. Digoxin is renally eliminated; P-glycoprotein-mediated renal secretion is the major clearance pathway. Kidney disease compounds both baseline digoxin accumulation and the effect of azithromycin-induced P-glycoprotein inhibition. A patient with Stage 3b chronic kidney disease (eGFR 30–44) on digoxin can experience digoxin toxicity within 48–72 hours of starting azithromycin.
Patients taking higher digoxin doses (>0.25 mg daily) are at elevated risk. Higher doses reduce the margin for error; even a 25% increase in blood level may cross into toxicity.
Patients on multiple P-glycoprotein inhibitors face compounded risk. Other drugs that inhibit P-glycoprotein include verapamil, diltiazem, amiodarone, clarithromycin, and some antiretrovirals. If a patient is already on verapamil for hypertension and then receives azithromycin for an infection, the additive P-glycoprotein inhibition is synergistic.
Patients with hypokalemia or hypomagnesemia are predisposed to digoxin toxicity. Low potassium and magnesium increase the affinity of digoxin for the Na-K ATPase, lowering the toxic threshold. Azithromycin does not directly cause electrolyte loss, but in patients with GI disease or on diuretics, concurrent hypokalemia amplifies digoxin toxicity risk.
A 72-year-old woman with systolic heart failure (ejection fraction 35%) and mild chronic kidney disease (eGFR 52 mL/min/1.73m²) is on digoxin 0.25 mg once daily, furosemide, and lisinopril. She develops a urinary tract infection and is prescribed azithromycin 500 mg on day 1, then 250 mg daily for 4 days (standard 5-day Z-pack course). Her baseline digoxin level is 1.2 ng/mL (therapeutic). By day 5 of azithromycin, her digoxin level rises to 2.8 ng/mL (toxic range). She develops nausea, visual disturbances (yellow-green halos around lights), and palpitations. Her ECG shows frequent premature ventricular contractions (PVCs) and a prolonged PR interval. She presents to the emergency department with suspected digoxin toxicity.
This scenario illustrates the compounding risk factors: advanced age, reduced renal function, and a standard antibiotic dose that was not adjusted for digoxin interaction. The interaction occurred within the typical 5-day course of azithromycin. With appropriate monitoring and dose adjustment beforehand, this admission would have been preventable.
A 68-year-old man with persistent atrial fibrillation is rate-controlled on digoxin 0.125 mg daily and metoprolol. He has normal renal function (eGFR 72 mL/min/1.73m²) and no baseline electrolyte abnormalities. He presents with community-acquired pneumonia (CAP) and is started on azithromycin 500 mg on day 1, then 250 mg daily for 4 additional days, plus amoxicillin-clavulanate. His baseline digoxin level is 1.1 ng/mL. On day 4 of azithromycin, he reports mild nausea and slight dyspnea. His digoxin level is rechecked and found to be 2.1 ng/mL—now in the toxic range. His heart rate has risen from 65 bpm to 88 bpm despite the digoxin, suggesting toxicity-induced arrhythmia. Azithromycin is stopped, and his digoxin dose is reduced to 0.0625 mg daily. Within 48 hours of stopping azithromycin, his nausea resolves and his digoxin level returns to 1.4 ng/mL.
This scenario shows that even in a patient with preserved renal function, the interaction is clinically significant. Early recognition of subtle symptoms (nausea) and proactive monitoring prevented serious arrhythmia.
Before starting azithromycin, inform your doctor or pharmacist that you take digoxin. This is not optional—it should happen during every new antibiotic prescription. Your healthcare provider can assess whether azithromycin is the best choice or whether an alternative antibiotic (one that does not inhibit P-glycoprotein, such as amoxicillin for bacterial sinusitis) is appropriate.
If azithromycin is necessary, ask about baseline digoxin levels. A serum digoxin concentration should be drawn before starting azithromycin (or early in the course if it was recently drawn). This establishes your baseline and allows your doctor to compare with levels during and after azithromycin therapy.
Request digoxin dose reduction. Many clinicians empirically reduce digoxin dose by 25–50% during macrolide antibiotic therapy. For example, if you are on digoxin 0.25 mg daily, your doctor may lower it to 0.125 mg daily during azithromycin treatment. This compensates for the expected rise in digoxin levels and reduces toxicity risk. The dose should be increased back to baseline after azithromycin is completed.
Plan for repeat digoxin level monitoring. A serum digoxin level should be drawn 5–7 days after starting azithromycin (or at the end of the course if it is shorter) to assess whether levels have risen into the toxic range. If azithromycin is continued beyond 5 days, monitoring should occur weekly. After azithromycin is stopped, a final level should be drawn 5–7 days later to confirm that digoxin levels are returning to baseline.
Check your potassium and magnesium. Ask your doctor to check serum electrolytes, especially potassium, before starting azithromycin. Low potassium amplifies digoxin toxicity. If you are on diuretics, electrolyte supplementation or a potassium-sparing agent may be warranted during azithromycin therapy.
Consider alternative antibiotics. For many infections, alternatives to azithromycin exist that do not inhibit P-glycoprotein. For bacterial sinusitis, amoxicillin or amoxicillin-clavulanate are first-line options. For respiratory infections, doxycycline or fluoroquinolones may be suitable. For atypical infections where azithromycin is specifically indicated (e.g., Mycoplasma pneumoniae), the risk-benefit calculation may still favor azithromycin use with close monitoring, but your doctor should make this decision explicitly.
Contact your healthcare provider immediately if you experience any of the following while taking azithromycin and digoxin:
Do not wait to see if symptoms resolve on their own. Digoxin toxicity can progress to fatal arrhythmias (ventricular fibrillation) within hours. If you experience chest pain, severe shortness of breath, or syncope, call emergency services (911 in the US) immediately.
Your medication safety is too important to leave to chance. If you take digoxin or any cardiac medication alongside antibiotics, use checkdruginteractions.com to verify your full medication list for interactions before you fill a new prescription. Our FDA-powered database scans over 250,000 drug labels to identify moderate and serious interactions that might be missed in a quick pharmacy consultation. Enter your medications now—it takes less than two minutes and could prevent a hospital visit.
CDI checks every pair across up to 20 drugs — backed by FDA and NIH data.
Drug interaction data sourced from U.S. FDA drug labeling via openFDA and the U.S. National Library of Medicine (NLM), National Institutes of Health. For informational purposes only. Always consult your pharmacist or physician before making any medication decisions.
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