Erythromycin: Uses, Dosage, Side Effects
Erythromycin is an older macrolide antibiotic still useful today. Doctors often choose it for people allergic to penicillin or for specific infections like some strep throat cases, certain skin infections, pertussis (whooping cough), and some eye infections in newborns. It comes in tablets, liquid, eye ointment, IV form, and topical creams. Knowing how it works and what to watch for makes it easier to use safely.
What erythromycin treats and how to take it
For adults the usual oral dose is 250–500 mg every 6–12 hours depending on the infection and the formulation. There’s also a 333 mg tablet often taken three times a day. For children dosing is weight-based—commonly 20–50 mg/kg per day divided into multiple doses. Neonatal eye ointment is used as a single application after birth in hospitals for certain infections. Always follow the exact dose your provider gives; different forms (base, ethylsuccinate, estolate) are not interchangeable without guidance.
Erythromycin works best on bacteria that make proteins in a way the drug blocks. That means it can treat several respiratory and skin infections, but resistance has grown in some germs. If your symptoms don’t improve in 48–72 hours, your doctor may switch antibiotics or order a culture.
Side effects and warnings
The most common side effects are stomach upset, nausea, vomiting, cramping, and diarrhea. These often happen early and may improve after a few days. Less common but serious issues include liver problems (jaundice), allergic reactions, and a rise in antibiotic-associated colitis (C. difficile). High doses or prolonged use can sometimes cause temporary hearing loss, especially in older adults or people with kidney problems.
Erythromycin can interact with many medicines because it affects the liver enzyme CYP3A4. That can raise levels of drugs like certain statins (simvastatin), some anti-seizure meds, warfarin, and others—raising the risk of side effects. It can also prolong the QT interval on an ECG, so avoid combining it with other QT-prolonging drugs if possible.
Pregnancy and breastfeeding: avoid the estolate form in pregnancy because it’s linked to liver injury. Other erythromycin forms are used when needed, but always check with your doctor. Small amounts pass into breast milk; most providers still advise using it if clearly necessary.
Practical tips: take erythromycin on an empty stomach for better absorption unless it upsets your stomach—then take with food. Finish the full course even if you feel better. Don’t skip doses. Store tablets at room temperature away from moisture and heat.
When to call a doctor: if you have severe diarrhea (especially with fever or blood), yellowing of the skin or eyes, hives, difficulty breathing, fainting, or a fast/irregular heartbeat. Also contact your provider if symptoms worsen or don’t start improving in a couple of days.
Final note: erythromycin is useful, but it’s not the right choice for every infection because of resistance and drug interactions. Use it only when prescribed, follow dosing exactly, and ask your provider or pharmacist about interactions with your other medicines.
