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Antibiotic interactions

Erythromycin and digoxin: antibiotic courses and digoxin concentration

Erythromycin is a widely used antibiotic and digoxin is a heart medicine with a narrow safety margin. The BNF says erythromycin increases the concentration of digoxin, advises monitoring digoxin concentration and rates the interaction severe. This guide explains the entry, which other antibiotics are listed and what the NHS tells patients to do.

Last checked: 2026-10-10

Key facts

At a glance.

  • BNF entry

    The BNF says erythromycin increases the concentration of digoxin, that the manufacturer advises monitor digoxin concentration, and that severity is severe with anecdotal evidence.

  • Clarithromycin too

    The BNF says clarithromycin increases the concentration of digoxin with advice to monitor digoxin concentration, and says trimethoprim increases it too, rated moderate.

  • NHS digoxin page

    The NHS digoxin page lists tetracycline, clarithromycin, erythromycin, rifampicin, trimethoprim and itraconazole among medicines for bacterial or fungal infections to tell your doctor about.

  • NHS erythromycin page

    The NHS erythromycin page lists domperidone, warfarin and rivaroxaban, pimozide or amisulpride, and statins among medicines that may not mix well, and is not a full list.

  • Check any new medicine

    The NHS says some medicines you can buy from a pharmacy or shop can also affect digoxin, and to ask a pharmacist before using antacids, kaolin or laxatives.

When this combination comes up

The NHS says erythromycin is mainly used to treat bacterial infections, including chest infections, dental abscesses and sexually transmitted infections, and is sometimes used for skin conditions such as acne and rosacea. Most people take it 2 to 4 times a day for a few days or weeks.

Digoxin is used for atrial fibrillation and other irregular heartbeats and to help manage heart failure symptoms, according to the NHS. It is often a long-term medicine, so the person is likely to already be taking it when an infection comes along and an antibiotic is prescribed by someone who may not see the full cardiac history.

This makes the moment an antibiotic is prescribed the key one for a check.

What the BNF says

The BNF interaction list for digoxin states that erythromycin increases the concentration of digoxin, with the manufacturer advising that digoxin concentration is monitored. The severity is severe and the evidence type is anecdotal. The clarithromycin entry has the same advice with a severe rating and anecdotal evidence, and trimethoprim is listed as increasing digoxin concentration with advice to monitor, rated moderate and with study evidence.

The BNF also notes that a long list of other medicines interacts with digoxin. Amiodarone is predicted to moderately increase exposure with advice to monitor and adjust the dose, and several medicines can increase the risk of bradycardia. The sensible reading is that digoxin is a medicine for which any new prescription deserves a check.

What the NHS tells patients

The NHS digoxin page says some medicines can affect the way digoxin works or increase the risk of side effects, and asks you to tell your doctor about any other medicines. It names medicines used to treat bacterial or fungal infections: tetracycline, clarithromycin, erythromycin, rifampicin, trimethoprim and itraconazole. It adds that you will need regular blood tests to check your kidneys and the amount of potassium, magnesium and calcium.

The page on side effects says to call your doctor or NHS 111 now if you have more than 2 of the common side effects, because you could have too much digoxin in your blood, and to call 999 or go to A&E for a fast heart rate or palpitations, shortness of breath, dizziness or light-headedness.

  • Say you take digoxin whenever an antibiotic is prescribed.

  • Ask whether a digoxin level or other check is needed during the course.

  • Report new dizziness, sickness, diarrhoea or vision changes promptly.

  • Call 999 for a fast heart rate, breathlessness or light-headedness.

Practical steps

Mention digoxin at the point of prescribing, at the pharmacy counter and to dentists, because dental abscesses are among the infections the NHS lists for erythromycin. If an antibiotic has been started before the combination was noticed, contact your GP, pharmacist or NHS 111 the same day. Do not stop digoxin yourself.

The sources read for this guide do not give a timetable for checking levels, so the plan comes from the prescriber. Keep any appointment for blood tests, and finish antibiotic courses as directed unless a clinician changes the plan.

NHS and private routes

GP practices, pharmacies and out-of-hours services check prescriptions against the BNF in the NHS. Private clinics and online prescribers use the same references but only see what you tell them, so the medicine list is again the safeguard. This site has separate guides to digoxin toxicity, the digoxin level test and the related digoxin and verapamil interaction.

Frequently asked

Questions people ask.

Quick, plain-English answers to the questions we hear most.

  • Can I take erythromycin if I take digoxin?

    It can be used, but the BNF says erythromycin increases digoxin concentration and rates the interaction severe, with advice to monitor digoxin concentration.

  • Is clarithromycin the same?

    The BNF gives the same advice for clarithromycin, and lists trimethoprim as increasing digoxin concentration too, rated moderate.

  • What symptoms suggest too much digoxin?

    The NHS says more than 2 of the common side effects, such as dizziness, sickness, diarrhoea or vision changes, could mean too much digoxin. Call your doctor or 111.

  • What needs an emergency response?

    The NHS says a fast heart rate or palpitations, shortness of breath, dizziness or light-headedness need 999 or A&E.

  • Who is more sensitive to digoxin?

    The NHS says children, older people and people with kidney disease or an underactive thyroid can be more sensitive.

  • Should I check over-the-counter products?

    Yes. The NHS says some medicines bought from a pharmacy or shop can affect digoxin, and to ask a pharmacist before using antacids, kaolin or laxatives.

  • Do I need a blood test during the antibiotic?

    The BNF advises monitoring digoxin concentration. Whether and when is decided by your prescriber.

  • Is St John's wort a concern?

    The NHS digoxin page says St John's wort can affect how digoxin works and to tell a pharmacist or doctor if you use it.

Where this comes from

Sources and checking.

This guide is for information, not medical advice.

Your GP or consultant knows your history and can tell you which parts apply to you. If your symptoms are severe, rapidly worsening, or come with red-flag features, seek urgent medical care. Figures and availability change, so treat them as a guide and confirm with the provider.

Published 2026-10-10, next review 2027-10-10.

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