Erythromycin – Classic macrolide antibiotic for penicillin-allergic patients.
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What is Erythromycin?
Erythromycin is a well-established macrolide antibiotic that remains valuable for treating various bacterial infections, particularly in patients allergic to penicillins. Despite newer alternatives, it continues to be widely used due to its proven effectiveness and broad spectrum of activity.
Book an online consultation if you’re experiencing bacterial infections and are allergic to penicillin, have acne that may benefit from antibiotic treatment, or have respiratory infections that may require macrolide therapy. Our GPs can assess your symptoms and determine if Erythromycin is the appropriate antibiotic for your specific condition.
What is Erythromycin used for?
- Respiratory tract infections
- Skin and soft tissue infections
- Whooping cough (pertussis)
- Atypical pneumonia
- Acne vulgaris (topical and oral)
- Chlamydia infections
- Helicobacter pylori eradication (in combination)
- Gastroparesis (stomach motility disorder)
How does Erythromycin work?
A macrolide antibiotic that inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit, and also has prokinetic effects on gut motility by acting as a motilin receptor agonist.
Dosage and Administration
Adults
250-500mg four times daily, or 500mg-1g twice daily for slow-release preparations. Topical: apply twice daily.
Children
Age-based dosing: 2-8 years: 250mg four times daily. 8+ years: adult dose. Newborns require specialist dosing.
Important Notes
- Take on an empty stomach for best absorption (1 hour before or 2 hours after food).
- Can be taken with food if stomach upset occurs, but absorption may be reduced.
- Complete the full course even if symptoms improve.
- Topical preparations for acne should be applied to clean, dry skin.
Side Effects
Common Side Effects
- Nausea and vomiting
- Abdominal pain and cramping
- Diarrhoea
- Loss of appetite
- Skin rash
- Headache
Serious Side Effects
Seek immediate medical attention if you experience:
- Heart rhythm changes (QT prolongation)
- Severe diarrhoea (C. difficile infection)
- Liver problems
- Hearing loss (with high doses or IV use)
- Severe allergic reactions
- Myasthenia gravis worsening
Important Warnings
- Tell your GP if you have heart rhythm problems, liver disease, or myasthenia gravis.
- May cause dangerous heart rhythm changes—avoid with other QT-prolonging drugs.
- Interacts with many medications—inform GP of all medicines you take.
- Can worsen muscle weakness in myasthenia gravis patients.
- May increase risk of pyloric stenosis in newborn babies.
Drug Interactions
Tell your GP if you're taking any of the following medications:
- Warfarin—significantly increases bleeding risk.
- Statins (simvastatin, atorvastatin)—increased risk of muscle problems.
- Digoxin—may increase digoxin levels and toxicity.
- Carbamazepine and phenytoin—may increase levels of these drugs.
- Ciclosporin—may increase ciclosporin levels.
- Theophylline—may increase theophylline levels and toxicity.
Frequently Asked Questions
Why is Erythromycin often prescribed for people allergic to penicillin?
Erythromycin is a macrolide antibiotic with a completely different structure from penicillins, making it safe for people with penicillin allergies.
Why does Erythromycin cause stomach upset?
Erythromycin stimulates gut motility, which can cause cramping and nausea. Taking it with food can help, though this may reduce absorption slightly.
Can Erythromycin be used for acne?
Yes, both topical and oral erythromycin are effective for acne by reducing acne-causing bacteria and inflammation. Topical forms have fewer side effects.
How is Erythromycin different from newer macrolides like Azithromycin?
Newer macrolides like Azithromycin have better tolerability, fewer drug interactions, and more convenient dosing, but Erythromycin remains effective and is often less expensive.
Medically Reviewed by: Mohammed Hassan - Independent Prescriber
Last Updated: 2025-01-14