# Erythromycin.net

> Independent, non-commercial reference on erythromycin, the original macrolide antibiotic: what it treats, adult and pediatric dosing, eye ointment and topical use, side effects, drug interactions, pregnancy, mechanism of action, history, and comparisons with azithromycin and clarithromycin. Content is based on FDA labeling, CDC, WHO, AAP and BNF guidance. Educational only — not medical advice.

Key facts:

- Drug class: macrolide antibiotic (14-membered lactone ring); binds 23S rRNA in the 50S ribosomal subunit; mainly bacteriostatic; strong CYP3A4 inhibitor; can prolong the QT interval.
- Usual adult oral dose (base/stearate): 250 mg every 6 h, 333 mg every 8 h, or 500 mg every 12 h; up to 4 g/day. 400 mg ethylsuccinate ≈ 250 mg base.
- Usual pediatric oral dose: 30–50 mg/kg/day in divided doses; may be doubled for severe infection (max 4 g/day). Avoid oral erythromycin for pertussis in infants < 1 month (pyloric stenosis risk) — azithromycin preferred.
- Eye ointment 0.5%: ~1 cm ribbon up to 6 times daily; newborn prophylaxis is a single 1 cm ribbon in each eye.
- Pregnancy: estolate salt contraindicated; for chlamydia in pregnancy CDC 2021 recommends azithromycin (amoxicillin alternative).
- Discovered 1949 by Abelardo Aguilar (Iloilo, Philippines); introduced by Eli Lilly in 1952.

Each page shows a last-updated date. Internal URLs are extensionless.

## Main pages

- [Erythromycin: Uses, Dosage, Side Effects & How It Works](https://erythromycin.net/): Erythromycin explained: what it treats, adult and child dosage, eye ointment and acne use, side effects, interactions, and how it compares with azithromycin. Independent, non-commercial.

## Dosage & use

- [Erythromycin Dosage for Adults & Children: Dosing Chart](https://erythromycin.net/usage/): Erythromycin dosage at a glance: 250 mg, 333 mg and 500 mg adult regimens, mg/kg dosing for children, dosing by infection, IV, eye ointment and acne gel, plus food timing.
- [Erythromycin Dosage for Children: mg/kg & Syrup Guide](https://erythromycin.net/usage/pediatric-dosing): Erythromycin pediatric dosing explained: 30–50 mg/kg/day, a weight-based table, suspension strengths, how to convert mg to mL, and infant safety warnings.
- [Erythromycin Eye Ointment Dosage: How Much & How Often](https://erythromycin.net/usage/eye-ointment): Erythromycin 0.5% eye ointment dosing: 1 cm ribbon up to 6 times daily, newborn prophylaxis, conjunctivitis, blepharitis, tube size, storage and side effects.
- [Erythromycin for Acne: Gel, Oral Dose & How Long to Use](https://erythromycin.net/usage/acne): How to use erythromycin for acne: 2% gel or solution twice daily with benzoyl peroxide, oral dose when needed, results in 6–12 weeks, resistance and when to switch.
- [Erythromycin for Gastroparesis: Dose, IV vs Oral & Evidence](https://erythromycin.net/usage/gastroparesis): Erythromycin for gastroparesis: low oral doses (40–250 mg before meals), IV 1–3 mg/kg, why it works (motilin agonist), tachyphylaxis, QT cautions and alternatives.
- [Erythromycin for Dental Infection: Dosage & Duration](https://erythromycin.net/usage/dental-infections): Erythromycin for tooth infections: adult dose 250–500 mg four times daily or 500 mg–1 g twice daily, children's dosing, how many days, and why drainage matters.

## Safety

- [Erythromycin Safety: Side Effects, Warnings & Contraindications](https://erythromycin.net/safety/): Erythromycin safety profile: common GI side effects, QT prolongation, liver injury, hearing loss, contraindications, CYP3A4 drug interactions, pregnancy and lactation.
- [Erythromycin Side Effects: Common, Serious & What to Do](https://erythromycin.net/safety/side-effects): Erythromycin side effects explained: why it upsets the stomach, how to reduce GI upset, serious risks like QT prolongation and liver injury, and when to stop.
- [Erythromycin Drug Interactions: CYP3A4 Interaction Table](https://erythromycin.net/safety/interactions): Erythromycin drug interactions explained: statins, warfarin, theophylline, carbamazepine, DOACs, calcium channel blockers and QT-prolonging drugs — with management advice.
- [Erythromycin QT Prolongation: Risk, ECG Monitoring & Torsades](https://erythromycin.net/safety/qt-prolongation): Does erythromycin prolong the QT interval? Yes — how much, who is at risk (hypokalemia, CYP3A4 inhibitors, other QT drugs), ECG monitoring and safer alternatives.
- [Erythromycin and Alcohol: Can You Drink on It?](https://erythromycin.net/safety/alcohol): Can you drink alcohol with erythromycin? No dangerous reaction like metronidazole, but alcohol can worsen stomach upset and may hit harder. Practical tips.
- [Erythromycin in Pregnancy, Breastfeeding & Newborns](https://erythromycin.net/safety/pregnancy): Is erythromycin safe in pregnancy and breastfeeding? Safety data, the estolate warning, PPROM use, newborn eye ointment and how it compares with azithromycin.

## Pharmacology & background

- [Erythromycin Basics: Drug Class, Spectrum & Resistance](https://erythromycin.net/basics/): What kind of antibiotic is erythromycin? Macrolide class, bacterial spectrum (gram-positive, atypicals), resistance mechanisms and where it fits in practice today.
- [How Does Erythromycin Work? Mechanism of Action](https://erythromycin.net/basics/mechanism): How erythromycin works: it binds the bacterial 50S ribosome and stalls protein synthesis. Why it spares human cells, its spectrum, resistance and MRSA limits.
- [Is Erythromycin a Macrolide? Macrolide Antibiotics List](https://erythromycin.net/basics/macrolides): Yes — erythromycin is the original macrolide antibiotic. Full list of macrolides (azithromycin, clarithromycin, roxithromycin, fidaxomicin…), how they work, and how they compare.
- [Who Discovered Erythromycin? History From 1949 to Today](https://erythromycin.net/basics/history): Erythromycin was discovered in 1949 by Filipino scientist Abelardo Aguilar and launched by Eli Lilly in 1952. Full timeline: esters, azithromycin, clarithromycin, ketolides.

## Comparisons & FAQ

- [Erythromycin FAQ: Alcohol, Food, Pregnancy, Missed Doses](https://erythromycin.net/faq/): Answers to common erythromycin questions: Can I drink alcohol? Take it with food? Is it safe in pregnancy? How fast does it work? What if I miss a dose?
- [Erythromycin vs Azithromycin: Same Class? Key Differences](https://erythromycin.net/faq/erythromycin-vs-azithromycin): Are erythromycin and azithromycin the same? Both are macrolides, but they differ in dosing (4× daily vs once), side effects, interactions and cost. Side-by-side table.
- [Erythromycin vs Clarithromycin: Differences & Which to Use](https://erythromycin.net/faq/erythromycin-vs-clarithromycin): Erythromycin vs clarithromycin compared: dosing frequency, GI side effects, CYP3A4 interactions, pregnancy, H. pylori use and when each is preferred. Quick table.

## Optional

- [About & editorial policy](https://erythromycin.net/about): About Erythromycin.net: an independent, non-commercial erythromycin reference. Our sources, update process, corrections policy and disclosures.
- [Privacy policy](https://erythromycin.net/privacy): Privacy policy for Erythromycin.net: what data is collected (Google Analytics aggregate statistics), cookies, your choices and how to contact us.
- [Sitemap](https://erythromycin.net/sitemap.xml): XML sitemap of all pages