A macrolide antibiotic
Erythromycin
A macrolide antibiotic often used when penicillin cannot be given.
What is Erythromycin?
Erythromycin is a macrolide antibiotic used for chest, skin, dental and other infections, and is a common alternative for people who are allergic to penicillin. It can also be prescribed for some childhood infections and, at times, to help the gut empty. It commonly causes stomach upset and interacts with several other medicines, so it is taken exactly as directed.
Education and reference only. This is a plain-language guide to Erythromycin — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Erythromycin is a long-established macrolide antibiotic used across the UK health service. It is a particularly useful option for people who cannot take penicillin, covering many of the same chest, throat, skin and dental infections. It is also used in some specific situations, such as certain infections in children and pregnancy. It tends to upset the stomach and has several important drug interactions, which influence when it is chosen.
How it works
Erythromycin stops bacteria from making the proteins they need to grow and multiply, by binding to part of their protein-building machinery (the ribosome). This halts bacterial growth and lets the body's defences clear the infection. Because it acts differently from penicillins, it works in people who are penicillin-allergic.
Company & origin
Originated / developed by: Eli Lilly.
Discovered in the 1950s from a soil bacterium found in the Philippines and developed by Eli Lilly, it was the first macrolide antibiotic and an important alternative to penicillin.
Practical use
How to take Erythromycin
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it as directed on the label, spacing the doses evenly through the day.
- If it upsets your stomach, taking it with food can help, though some products are best taken before food — follow the specific instructions.
- Complete the full course even once you feel better.
- Tell your prescriber and pharmacist about all your other medicines, including statins and any heart medicines, before starting.
- Report a fast, pounding or irregular heartbeat, fainting, or severe diarrhoea.
Weighing it up
Advantages & disadvantages of Erythromycin
Advantages
- A reliable alternative for people who are allergic to penicillin.
- Long-established with a well-understood safety profile, and usable in pregnancy when needed.
- Available as tablets and a liquid, so it suits both adults and children.
Disadvantages
- Frequently causes stomach upset — nausea, cramps and diarrhoea.
- Interacts with many other medicines, including some statins, increasing the risk of side effects.
- Can affect the heart's electrical rhythm (QT prolongation), so it is used with care in people at risk or on other QT-affecting medicines.
Practical use
Good to know
Stomach upset — nausea, cramps and diarrhoea — is common, partly because erythromycin also stimulates gut movement. It is taken as directed, and following the timing instructions matters. It interacts with several widely used medicines, including some statins and medicines that affect the heart's rhythm, so the prescriber and pharmacist check what else you take.
Who should not take it / use with caution
- People with a known allergy to macrolide antibiotics such as erythromycin, clarithromycin or azithromycin.
- People with certain heart-rhythm problems, including a long-QT condition, or those on other medicines that affect the heart's rhythm — used with caution.
- Anyone taking simvastatin (the statin is normally stopped for the duration of the course because of a serious muscle-damage risk) or an ergotamine-type migraine medicine (risk of ergot toxicity) — these must not be combined.
- Used with care in significant liver disease, and the prescriber reviews suitability where it interacts with other essential medicines.
Monitoring
- Mainly clinical — checking the infection responds and watching for stomach and heart symptoms.
- Heart rhythm in people at higher risk, especially when combined with other QT-affecting medicines.
- Closer clotting (INR) checks if taken with warfarin.
Side effects
- Nausea, vomiting, tummy cramps and diarrhoea are common.
- Altered taste and, occasionally, thrush.
- Rarely, a change in the heart's rhythm (which can cause palpitations or fainting), liver inflammation, or hearing changes — these should be reported.
Key interactions
- Must not be taken with simvastatin — the statin is normally stopped for the duration of the erythromycin course (serious muscle-damage risk); other statins such as atorvastatin may also need pausing or changing.
- Must not be used with ergotamine-type migraine medicines (risk of ergot toxicity).
- Adds to the risk of heart-rhythm disturbance with other QT-prolonging medicines (some antipsychotics, antidepressants and other antibiotics).
- Can raise levels of medicines including warfarin, some seizure medicines and certain others — the prescriber checks for these.
Available as: Tablets and an oral suspension (liquid); a form for hospital drip use also exists.
Answers
Erythromycin: frequently asked questions
Why is erythromycin given to people allergic to penicillin?
Erythromycin is a macrolide, a different class of antibiotic that kills bacteria in a different way from penicillins. Because it is unrelated to penicillin, it is safe for most people with a penicillin allergy and covers many of the same common infections, which makes it a useful alternative.
Why does erythromycin upset my stomach so often?
As well as fighting bacteria, erythromycin stimulates movement in the gut, which commonly causes nausea, cramps and diarrhoea. Taking it with food can ease this for many people. If the upset is severe or you have very watery or bloody diarrhoea, contact your prescriber.
Can I take erythromycin with my cholesterol tablet (statin)?
Sometimes not. Erythromycin can raise the levels of certain statins, such as simvastatin, increasing the risk of muscle side effects. Your prescriber or pharmacist may pause or change the statin while you take erythromycin, so always tell them what you are on.
What heart-rhythm warning is linked to erythromycin?
Erythromycin can affect the heart's electrical rhythm (QT prolongation), which is usually harmless but can rarely cause palpitations or fainting, especially alongside other medicines with the same effect. Tell your prescriber about all your medicines and any heart-rhythm condition, and report a fast or irregular heartbeat.
What is the difference between erythromycin and Erythroped?
They are the same medicine — erythromycin is the active-ingredient name and Erythroped is a brand name. Generic erythromycin contains the identical active ingredient.
The wider class
About Macrolides
Erythromycin belongs to the macrolides class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF: Erythromycin.
- NICE CKS: Erythromycin.
- MHRA Drug Safety Update: macrolide antibiotics and QT prolongation.
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