Purmycin is an erythromycin suspension, 125 mg per 5 ml, a macrolide antibiotic often prescribed for children. It treats chest, throat, ear, skin and dental infections, and is a common alternative for people allergic to penicillin. Complete the full course, and expect some stomach upset.
What is Purmycin?
Purmycin contains erythromycin, supplied as a 125 mg/5 ml suspension — a form that makes it convenient for children and for anyone who struggles with tablets.
Erythromycin is a macrolide antibiotic. It works differently from the penicillins: rather than attacking the bacterial cell wall, it binds to the bacterial ribosome, the machinery a cell uses to build proteins. Without the ability to make proteins, the bacterium cannot grow or multiply, and the immune system clears the infection.
Human ribosomes are structurally different, which is why the antibiotic acts on bacteria and not on us.
Erythromycin’s most important practical role in South Africa is as the alternative for people allergic to penicillin. Penicillin allergy is common, and macrolides cover many of the same organisms — chest, throat, ear and skin infections — through a completely unrelated mechanism, so there is no cross-reactivity.
Newer macrolides such as the azithromycin in Azrotrin and clarithromycin are derived from erythromycin and are better tolerated, but erythromycin remains widely used — particularly as a paediatric suspension.
It is a Schedule 4 prescription medicine.
What is Purmycin commonly used for?
Erythromycin is prescribed for:
- Chest infections, including bronchitis and community-acquired pneumonia.
- Atypical pneumonia, caused by organisms such as Mycoplasma and Legionella that penicillins do not cover.
- Throat infections, including streptococcal tonsillitis.
- Middle ear infections in children.
- Sinusitis.
- Skin and soft tissue infections, including impetigo and acne.
- Dental infections, particularly in penicillin-allergic patients.
- Whooping cough (pertussis), both as treatment and to protect close contacts.
- Some sexually transmitted infections, including chlamydia in specific circumstances.
- Diphtheria and some other less common infections.
It does nothing for colds, flu or most coughs and sore throats, which are viral. Antibiotics have no effect on viruses, and taking one unnecessarily gives you the side effects with none of the benefit while contributing to resistance.
Whooping cough deserves separate mention. Erythromycin is used both to treat it and to protect household contacts, and it reduces spread to others even though it does not shorten the cough much once it is established. If a family member has been diagnosed, take the preventive course seriously — this protects infants, in whom whooping cough can be life-threatening.
How Purmycin fits into this medicine category
| Group | Examples | Common targets |
|---|---|---|
| Macrolides | Erythromycin (Purmycin), azithromycin, clarithromycin | Chest, throat, ear, skin; penicillin allergy |
| Broad-spectrum penicillins | Amoxicillin, amoxicillin-clavulanate | Chest, ear, throat, dental, urinary |
| Narrow-spectrum penicillins | Flucloxacillin | Skin — staphylococci |
| Sulfonamide combinations | Co-trimoxazole | Urinary, chest, PCP |
| Nitroimidazoles | Metronidazole | Anaerobic and dental infections |
See the antibiotics and antimicrobials hub.
What to check before using Purmycin
Shake the bottle well before every dose, and use the measuring device supplied — not a kitchen spoon. Paediatric doses are calculated by weight, and an inaccurate measure means an inaccurate dose.
Check whether your bottle needs refrigeration and note the expiry after opening; reconstituted antibiotic suspensions usually keep only a limited number of days.
Finish the whole course, even once symptoms improve.
Tell your prescriber or pharmacist if:
- You have liver disease. Erythromycin is processed by the liver.
- You have a heart rhythm problem, particularly a long QT interval, or a family history of sudden cardiac death.
- You have myasthenia gravis, which erythromycin can worsen.
- You are pregnant or breastfeeding.
- You take simvastatin or atorvastatin — erythromycin raises statin levels and the risk of muscle damage, so the statin is often paused; warfarin, where bleeding risk rises; digoxin; carbamazepine; theophylline; ciclosporin; or a medicine affecting heart rhythm.
Erythromycin interacts with more medicines than most antibiotics. It inhibits a major liver enzyme system, which raises the blood levels of a range of other drugs. Tell whoever prescribes it about everything you take, including anything bought over the counter.
Follow the dispensing label. This page does not set doses.
Possible cautions and when to ask a pharmacist or doctor
Stomach upset is common — nausea, cramping, vomiting and diarrhoea affect a substantial proportion of people, more than with newer macrolides. Erythromycin stimulates gut motility directly, which is the cause. Taking it with food usually helps; if it is intolerable, a different antibiotic can be substituted, so say so rather than abandoning the course.
Diarrhoea is frequent and usually mild. Severe, watery or bloody diarrhoea, especially with fever and especially if it begins after the course ends, can indicate Clostridioides difficile infection and needs medical attention.
Heart rhythm. Erythromycin can prolong the QT interval. This matters mainly for people with an existing rhythm problem or on other QT-prolonging medicines — report palpitations or fainting.
Liver effects are uncommon but recognised. Report yellowing of the skin or eyes, dark urine, pale stools or persistent abdominal pain.
If there is no improvement in two or three days, or things worsen, go back.
In infants, erythromycin has been associated with pyloric stenosis. Report persistent forceful vomiting in a young baby.
Seek urgent medical attention for facial or throat swelling, difficulty breathing, a rash that blisters or peels, severe or bloody diarrhoea, palpitations or fainting, yellowing of the skin or eyes, or an infection spreading despite treatment.
Related medicine guides
Frequently asked questions
What is Purmycin used for? Bacterial infections of the chest, throat, ears, sinuses, skin and teeth. It contains erythromycin, and is often used for people allergic to penicillin.
Can I take it if I am allergic to penicillin? Yes — that is one of its main roles. Erythromycin is a macrolide and works by a completely different mechanism, with no cross-reactivity.
Why does it upset my stomach? Erythromycin stimulates gut movement directly, so nausea and cramping are common. Taking it with food helps; tell your prescriber if it is intolerable.
How do I measure the dose for my child? Shake the bottle, use the syringe or cup supplied, and follow the amount on the label. Doses are calculated by weight.
Does it need to be kept in the fridge? Check your bottle — some reconstituted suspensions do, and they keep only a limited number of days once made up.
Will it help my cold? No. Colds and flu are viral, and antibiotics have no effect on viruses.