Erythromycin
In brief
- Systemic erythromycin is a prescription-only medicine (POM) in the UK.
- Erythromycin is used to treat bacterial infections such as respiratory, skin and soft-tissue infections, acne, and some eye infections. It is a macrolide antibiotic that works by inhibiting bacterial protein synthesis, thereby stopping the growth of susceptible bacteria.
- The usual dose depends on the condition and formulation: for adults, 250–500 mg every 6 hours orally is common; for children, 30–50 mg/kg/day in divided doses; topical acne treatment is usually a 2% solution or gel applied twice daily.
- The form of administration includes oral tablets, oral suspensions, delayed-release tablets, topical solution or gel, eye ointment, and powder for suspension.
- Erythromycin usually starts to work within 1–2 hours after oral dosing, although relief of infection symptoms may take longer.
- The duration of action is generally around 6 hours per dose for standard oral preparations, which is why it is often taken multiple times daily; treatment courses commonly last 7–14 days.
- Alcohol is not strictly contraindicated, but it is best avoided or limited because it may worsen stomach upset and increase the risk of side effects.
- The most common side effects are nausea, vomiting, abdominal cramps, and diarrhoea; some people may also experience rash, local irritation, or taste disturbances.
- Would you like to try erythromycin without a prescription?
Basic erythromycin information
- INN (international nonproprietary name): Erythromycin
- Brand names available in the United Kingdom: Erythromycin; Ilosone
- ATC code: J01FA01
- Forms and dosages: Oral tablets 250 mg, 500 mg; oral suspensions 125 mg/5 ml, 250 mg/5 ml; delayed-release tablets 250 mg; topical solution/gel 2%; eye ointment 5 mg/g; powder for suspension 125 or 250 mg/5 ml
- Registration status in the United Kingdom: Prescription-only medicine (POM) for systemic forms
- OTC / Rx classification: Prescription-only medicine (POM)
Erythromycin at a glance
In UK pharmacy practice, erythromycin usually appears in the same conversation as acne, skin infections, bacterial conjunctivitis, and respiratory infections.
Systemic erythromycin is a prescription-only medicine in the UK and is usually accessed through a GP, an NHS electronic prescription, or a private prescription.
Topical and eye products are also used. A pharmacy consultation is advisable, especially where interactions, allergies, or heart rhythm risks are possible.
What erythromycin is and where it fits in treatment
Erythromycin is a macrolide antibiotic used as a systemic antibacterial and in topical or ophthalmic forms.
It is the kind of medicine a prescriber may choose when a macrolide option is needed and the infection, age, or formulation makes it suitable.
- INN
- Erythromycin, the recognised international nonproprietary name.
- Macrolide class
- A well-known antibiotic family that includes erythromycin, azithromycin, and clarithromycin.
- ATC code J01FA01
- J01 means antibacterials for systemic use, FA means macrolides, and 01 identifies erythromycin.
- Practical meaning
- The code helps pharmacists tell whether a product is an oral antibiotic, a topical product, or an eye preparation.
Erythromycin formulations
Erythromycin is available in a small set of familiar formats.
| Formulation | Common strengths | Typical use | Packaging notes |
|---|---|---|---|
| Oral tablets | 250 mg, 500 mg | Adults and older children with suitable prescribing | Usually blister packs or film-coated tablets |
| Delayed-release tablets | 250 mg | Extended absorption for selected oral treatment plans | Commonly blister packed |
| Oral suspension | 125 mg/5 ml, 250 mg/5 ml | Paediatric dosing by weight | Bottles, often 60–100 ml |
| Powder for suspension | 125 mg/5 ml or 250 mg/5 ml after reconstitution | Prepared before paediatric use | Usually supplied in a bottle for mixing |
| Topical solution or gel | 2% | Acne and some skin infections | Usually a bottle or tube |
| Eye ointment | 5 mg/g | Ophthalmic infections such as bacterial conjunctivitis | Usually a tube |
Adults are more likely to be offered tablets, while children are more often prescribed an erythromycin suspension.
For acne, the 2% topical form is the product usually used.
Erythromycin eye ointment is a different product again, and the tube format matters because eye medicines are used in small amounts for short courses.
Brand names
Generic erythromycin is common in the UK, and Ilosone is a brand name.
How erythromycin is used in UK practice
In UK practice, it is used in a fairly predictable set of scenarios, both NHS and private, depending on the indication and local guidance.
- Respiratory infections such as pharyngitis, bronchitis, and sinusitis.
- Skin and soft-tissue infections where a macrolide is suitable.
- Acne vulgaris, especially with topical erythromycin products.
- Bacterial conjunctivitis and other ophthalmic infection use.
- Specialist use in gastroparesis-related gastroprotection contexts.
For a sore throat or chest infection, a prescriber may choose erythromycin when a macrolide is appropriate and the patient profile fits.
For acne, the topical solution or gel is the common pharmacy-facing product, not the oral tablet.
For eye infections, an erythromycin eye ointment may be selected because eye preparations are easy to apply and localised.
Choice over another antibiotic often comes down to tolerance, allergy history, heart rhythm risk, and whether the clinician wants a macrolide option.
Dosage by condition
That depends on the condition, the formulation, and whether the patient is a child or an adult.
| Condition | Adult dose | Paediatric dose | Usual duration |
|---|---|---|---|
| Respiratory infections | 250–500 mg every 6 hours by mouth | 30–50 mg/kg/day in 2–4 doses | 7–14 days |
| Skin and soft-tissue infections | 250–500 mg every 6 hours by mouth | 30–50 mg/kg/day in 2–4 doses | 7–10 days |
| Acne | Apply 2% solution or gel twice daily | Not typically used | Until improvement |
| Ophthalmic infection | Apply in the affected eye(s) every 6 hours | Safety under 2 months not established | Typically 7–14 days |
For children, the erythromycin suspension is usually the practical option because dosing can be matched to body weight.
For most infections, treatment lasts around 7 to 14 days, while acne treatment may continue for several weeks under guidance.
Pharmacists often check that the strength, the bottle size, and the instructions all match the intended course before handing the medicine over.
Dose adjustments, special populations, and safety checks
Children, older adults, and people with liver problems should always have the regimen checked carefully.
- Children
- Use suspensions and dose by weight, usually 30–50 mg/kg/day divided every 6 to 8 hours.
- Older adults
- No standard dose adjustment is specified, but hepatic function may need monitoring.
- Liver impairment
- Reduce the dose or extend the interval because erythromycin is metabolised hepatically.
- Renal impairment
- Routine adjustment is usually not needed unless the impairment is severe, when closer monitoring is sensible.
That practical checklist helps carers and patients spot when they should ask a prescriber or pharmacist rather than guess.
It is especially useful for family medicine cupboards, where an old bottle may no longer match the child’s current weight.
Contraindications and interaction risks
Some medicines simply should not be taken with erythromycin, and some health conditions make it a poor choice.
Do not use if there is a known macrolide allergy, a history of cholestatic jaundice or hepatic dysfunction with previous use, or concurrent use of medicines that significantly prolong the QT interval or are extensively metabolised by CYP3A4 and are contraindicated.
Check first if there is hepatic impairment, myasthenia gravis, heart arrhythmia, or a prolonged QT interval.
| Situation | What it means | Action |
|---|---|---|
| Macrolide allergy | Risk of a serious allergic reaction | Do not use |
| QT-prolonging medicines | Higher chance of heart rhythm problems | Do not use unless specifically directed by a prescriber |
| Prior cholestatic jaundice with erythromycin | History suggests recurrence risk | Do not use |
| Myasthenia gravis | Symptoms may worsen | Check first |
| Arrhythmia or prolonged QT interval | Heart rhythm monitoring may be needed | Check first |
Interaction screening is why pharmacists are so careful with erythromycin interactions and CYP3A4 concerns.
This matters especially when the patient is already taking long-term medicines for the heart, infections, or chronic conditions.
Side effects
Stomach upset is the big one, and it is the main reason some people stop and ring the pharmacy for advice.
- Nausea.
- Vomiting.
- Abdominal cramps.
- Diarrhoea.
- Rash.
- Local irritation with topical or oral forms.
- Taste disturbance.
- Transient hearing loss, especially at high IV or oral doses.
Most people only notice mild to moderate effects, but persistent diarrhoea, an allergic rash, or hearing changes need medical advice.
Missed doses, overdose concerns, and when to seek help
Take it as soon as remembered unless the next dose is nearly due.
Never double the next dose to make up for a missed one.
Overdose symptoms may include strong gastrointestinal upset and possible ototoxicity at high doses.
If an overdose is suspected, seek medical attention immediately.
That advice is especially important in households using erythromycin suspension, where measuring errors can happen during a busy evening.
Storage
| Form | Storage condition | User tip |
|---|---|---|
| Tablets and capsules | Store below 25°C and protect from moisture | Keep in the original pack away from sinks and steam |
| Suspensions | Refrigerate after reconstitution if the label says so | Shake before each dose |
| Topicals | Room temperature and avoid freezing | Do not leave in a hot car |
| Eye ointment | Store below 25°C | Discard the tube after the course ends |
A reconstituted suspension needs different handling from an unopened bottle.
Legal status and availability in the UK
Erythromycin is a prescription-only medicine (POM) in the UK.
In our online pharmacy, erythromycin is available without a prescription, with discreet delivery to the United Kingdom in 9–21 days.
Erythromycin versus common macrolide alternatives
Often the answer is formulation, local guidance, or a specific clinical reason rather than simple habit.
| Medicine | Typical advantage | Common reason to choose | Practical note |
|---|---|---|---|
| Erythromycin | Established macrolide option with oral, topical, and eye forms | Selected infections, acne, ophthalmic use, specialist contexts | More interaction checks are often needed |
| Azithromycin | Shorter courses and often better tolerated | Some respiratory and other infections | Common macrolide alternative |
| Clarithromycin | Shorter treatment durations and improved tolerability profiles in some cases | Selected infections where it fits guidance | Another common macrolide alternative |
Erythromycin still appears in prescribing and pharmacy catalogues because it remains useful in specific indications and formulations, particularly where a tablet, suspension, topical product, or eye ointment is needed.
Delivery across the United Kingdom
| City | Region | Delivery time |
|---|---|---|
| London | England | 9–21 days |
| Birmingham | England | 9–21 days |
| Manchester | England | 9–21 days |
| Leeds | England | 9–21 days |
| Liverpool | England | 9–21 days |
| Glasgow | Scotland | 9–21 days |
| Edinburgh | Scotland | 9–21 days |
| Cardiff | Wales | 9–21 days |
| Belfast | Northern Ireland | 9–21 days |
| Bristol | England | 9–21 days |
| Sheffield | England | 9–21 days |
| Nottingham | England | 9–21 days |
| Newcastle upon Tyne | England | 9–21 days |
| Leicester | England | 9–21 days |
Frequently asked questions about erythromycin
Can erythromycin tablets be used for acne?
Oral tablets are not the usual acne format; the 2% topical solution or gel is the more common acne product.
Is erythromycin eye ointment the same as the tablet?
No, the eye ointment is an ophthalmic product at 5 mg/g and is used differently from oral medicine.
Do children need a different dose?
Yes, children usually need suspension dosing by weight.
Can I take it with all my regular medicines?
Not always, because erythromycin has important interaction risks, especially with QT-prolonging medicines and CYP3A4-related contraindications.
What if I miss a dose?
Take it when remembered unless the next dose is near, and do not double up.
How should I store reconstituted suspension?
Follow the label, keep it refrigerated if instructed, and shake it before each use.
