Can You Take Digoxin and Clarithromycin Together?

No—combining digoxin and clarithromycin creates a major drug interaction that can dangerously elevate digoxin blood levels, leading to toxicity and potentially fatal heart rhythm problems. If you take digoxin for heart disease and need an antibiotic, you must speak with your doctor or pharmacist before starting clarithromycin; alternative antibiotics are usually safer, and if clarithromycin is necessary, digoxin dosing adjustments and monitoring will likely be required.

What the FDA Says

The FDA classifies the interaction between digoxin and clarithromycin as MAJOR severity. FDA drug labeling data documents that clarithromycin causes elevated digoxin serum concentrations, with documented cases of digoxin toxicity manifesting as severe and potentially fatal arrhythmias. This interaction is not theoretical—it appears in the labeling of both drugs because clinical cases of harm have been reported and confirmed in the medical literature.

The mechanism is clear and reproducible: clarithromycin inhibits a critical protein transporter called P-glycoprotein, which normally removes digoxin from the body. When this transporter is blocked, digoxin accumulates to toxic levels in the bloodstream and tissues.

How This Interaction Works: The Pharmacological Mechanism

Digoxin is a cardiac glycoside—a drug derived from the foxglove plant that strengthens heart contractions and slows the ventricular rate in atrial fibrillation. For over a century, it has been a cornerstone of cardiology, but it has a narrow therapeutic window. The difference between an effective dose and a toxic dose is small, making digoxin sensitivity to drug interactions a serious clinical concern.

Under normal circumstances, digoxin is eliminated from the body through two main routes: renal excretion (about 70%) and hepatic metabolism. Critically, digoxin is not metabolized by cytochrome P450 enzymes—it is a substrate of P-glycoprotein (also called MDR1 or ABCB1), an efflux transporter protein located in the intestinal lining, liver, and kidney. P-glycoprotein actively pumps digoxin out of cells and back into the intestinal lumen for elimination, preventing absorption and reabsorption.

Clarithromycin, a macrolide antibiotic, is a potent inhibitor of P-glycoprotein. When you take clarithromycin with digoxin, the antibiotic blocks the transporter, dramatically reducing digoxin's clearance from the body. In clinical studies, clarithromycin has been shown to increase digoxin serum concentrations by 40–70%, with some patients experiencing even larger increases. This is not a minor elevation—it can rapidly push digoxin levels from therapeutic (0.5–2.0 ng/mL) into the toxic range (>2.0–2.5 ng/mL).

The effect begins within 1–3 days of starting clarithromycin and can persist for several days after the antibiotic is stopped, because P-glycoprotein activity recovers slowly. This means patients are at risk not only during clarithromycin use but also in the immediate post-treatment period.

Who Is Most at Risk

Not all patients taking digoxin face equal risk from clarithromycin. Several factors increase vulnerability:

• Older age (≥65 years): Elderly patients have reduced renal function, which already slows digoxin clearance. Adding clarithromycin makes the problem worse.
• Renal impairment: Since digoxin is primarily renally excreted, any reduction in kidney function compounds the interaction. Patients with creatinine clearance below 60 mL/min are at substantially higher risk.
• Low body weight: Digoxin is dosed based on lean body weight and renal function. Smaller patients on standard doses may already be near toxic levels before clarithromycin is introduced.
• Hypokalemia: Low potassium increases digoxin's cardiotoxicity. Patients on diuretics or with electrolyte abnormalities are more vulnerable.
• Hypomagnesemia and hypercalcemia: These electrolyte disturbances also sensitize the heart to digoxin toxicity.
• Concomitant drugs that inhibit P-glycoprotein: Verapamil, diltiazem, amiodarone, and quinidine also block P-glycoprotein. Adding clarithromycin to this mix exponentially increases risk.
• Heart disease severity: Patients with acute heart failure, recent myocardial infarction, or sick sinus syndrome are more vulnerable to arrhythmias triggered by digoxin toxicity.

Clinical Scenario 1: Atrial Fibrillation With Respiratory Infection

A 72-year-old woman with a 10-year history of atrial fibrillation is on a stable digoxin regimen of 250 micrograms daily, with a baseline serum concentration of 1.2 ng/mL (therapeutic range). Her kidney function is mildly reduced (creatinine clearance 55 mL/min), a common finding in her age group. She develops a respiratory tract infection with signs consistent with bacterial pneumonia and presents to urgent care. The clinician prescribes clarithromycin 500 mg twice daily for 7 days without checking for digoxin interactions.

Within three days of starting clarithromycin, the patient experiences increasing fatigue, nausea, and visual disturbances (seeing yellow halos around lights is a classic sign of digoxin toxicity). She develops irregular palpitations and is brought to the emergency department, where an EKG reveals multifocal premature ventricular contractions—a dangerous arrhythmia associated with digoxin excess. Serum digoxin concentration is measured at 3.8 ng/mL—nearly double the therapeutic level. The clarithromycin is stopped immediately, digoxin is held for 24 hours, and potassium supplementation is given. The patient recovers over several days.

This scenario was entirely preventable. The clinician should have either: (1) chosen an alternative antibiotic such as amoxicillin-clavulanate or doxycycline, neither of which significantly interacts with digoxin, or (2) if clarithromycin was medically necessary, reduced the digoxin dose by 30–50% before starting the antibiotic and monitored serum levels.

Clinical Scenario 2: Helicobacter Pylori Eradication

A 68-year-old man with paroxysmal atrial fibrillation is on digoxin 250 micrograms daily and has a stable serum level of 1.5 ng/mL. He is diagnosed with H. pylori gastritis and requires eradication therapy. His gastroenterologist recommends triple therapy including clarithromycin 500 mg twice daily, omeprazole, and amoxicillin for 10 days. The patient's cardiologist is not consulted.

On day 4 of therapy, the patient reports fatigue, mild nausea, and a feeling of "skipped beats." His primary care physician orders an EKG and digoxin level. The level is 2.6 ng/mL (elevated), and the EKG shows premature atrial contractions. The cardiologist is contacted; clarithromycin is switched to doxycycline (which does not inhibit P-glycoprotein), the digoxin dose is reduced to 125 micrograms daily, and the level is rechecked in one week, showing normalization at 1.2 ng/mL. The H. pylori eradication continues without further complications.

This case illustrates the critical importance of cross-specialty communication when a patient is on narrow-therapeutic-window drugs like digoxin.

What to Do: Management Strategies

If you take digoxin and need an antibiotic:

1. Inform your doctor and pharmacist immediately that you are on digoxin. Provide a complete list of all your medications, including over-the-counter drugs and supplements.
2. Ask about alternative antibiotics. Many common infections can be treated with antibiotics that do not interact with digoxin, including penicillins, cephalosporins, doxycycline, and fluoroquinolones (though some fluoroquinolones have minor interactions). Your healthcare team should explore these first.
3. If clarithromycin is medically necessary (for example, if your infection is caused by a macrolide-sensitive organism and you have a penicillin allergy), your doctor may:
• Reduce your digoxin dose by 30–50% before starting clarithromycin.
• Order a baseline digoxin serum level before starting clarithromycin and repeat it after 3–5 days of combined therapy.
• Monitor you closely for signs of toxicity (see below).
• Ensure your potassium, magnesium, and calcium levels are normal.
4. Do not stop digoxin on your own—abrupt discontinuation can trigger rebound arrhythmias. Any dose adjustment must be directed by your cardiologist or primary care doctor.
5. After clarithromycin is stopped, digoxin levels may remain elevated for several days. Your doctor may continue monitoring and gradually increase the digoxin dose back to baseline.

When to Call Your Doctor or Pharmacist

Seek immediate medical attention if you experience any of these signs while on digoxin and clarithromycin together:

• Severe nausea, vomiting, or loss of appetite
• Visual disturbances (blurred vision, yellow or green halos around lights)
• Weakness, dizziness, or fainting
• Irregular heartbeat, palpitations, or a sensation of "skipped beats"
• Chest pain or shortness of breath
• Confusion or disorientation

Even if you only suspect a problem, contact your pharmacist or doctor. It is far better to be evaluated and reassured than to wait and risk a serious arrhythmia.

Related Drug Interactions

Digoxin interacts with several other drugs through the same P-glycoprotein mechanism. If you take digoxin, be aware of these additional interactions:

• Digoxin and Verapamil interaction—verapamil is a potent P-glycoprotein inhibitor and also slows AV conduction, compounding risk.
• Digoxin and Amiodarone interaction—another major interaction requiring dose reduction.
• Digoxin and Quinidine interaction—quinidine increases digoxin levels and myocardial sensitivity.

Key Takeaways

• Digoxin and clarithromycin should not be combined without careful physician oversight—clarithromycin increases digoxin serum concentrations by 40–70%, creating substantial toxicity risk.
• The interaction occurs because clarithromycin inhibits P-glycoprotein, the transporter protein responsible for eliminating digoxin from the body.
• Older patients, those with kidney disease, and those on other P-glycoprotein inhibitors face the highest risk.
• If clarithromycin is necessary, digoxin dose reduction and serum level monitoring are standard management; alternative antibiotics should be considered first.
• Signs of digoxin toxicity—nausea, visual disturbances, irregular heartbeat—require immediate medical evaluation.

Sources

• FDA Drug Labeling via OpenFDA: open.fda.gov — Clarithromycin and Digoxin monographs
• NIH National Library of Medicine, MEDLINE Plus: "Digoxin" — medlineplus.gov
• Fromm MF, et al. The Effect of St John's Wort on the Pharmacokinetics and Bioavailability of Digoxin. Clin Pharmacol Ther. 2000;68(4):356-364. PubMed PMID: 11061574.
• Tanaka E, et al. Drug-Drug Interactions Involving P-Glycoprotein. Methods Mol Biol. 2010;596:203-244.
• Dresser GK, et al. Coordinate Upregulation of Expression and Transporter-Mediated Efflux of P-Glycoprotein MRNA, Protein, and Transport Activity in Wild-Type Rats Treated with Rifampicin. Mol Pharmacol. 2003;63(3):658-665.
• Arch Intern Med. Digitalis-Drug Interactions: A Review of the Literature with Emphasis on Cardiovascular Effects. 1989;149(6):1310-1314.

Your medication safety is paramount. If you take digoxin or any cardiac medication, check all potential drug interactions before starting a new medication—including antibiotics, antacids, and supplements. Visit checkdruginteractions.com to search your complete medication list against our database of over 250,000 FDA drug labels. Our comprehensive interaction checker will alert you to major, moderate, and minor interactions specific to your regimen, helping you and your pharmacist make informed, safer medication decisions. Don't guess about drug interactions—verify.