Erythromycin
Generic Name: Erythromycin
Brand Names: E-Mycin, Ery-Tab, EES
Erythromycin is a macrolide antibiotic used for respiratory infections and as an alternative to penicillin.
Drug Class
Macrolide Antibiotic
Pregnancy
Category B — Animal studies have not shown fetal risk; no adequate well-controlled studies in pregnant women. Generally considered one of the safer antibiotics during pregnancy, though the estolate salt form is not recommended due to hepatotoxicity risk.
Available Forms
Oral tablet (250 mg, 500 mg), Oral delayed-release capsule (250 mg), Oral suspension (200 mg/5 mL, 400 mg/5 mL), Ophthalmic ointment (0.5%), Topical gel (2%), Topical solution (2%), IV injection (500 mg, 1 g vials)
What It's Used For
Dosage Quick Reference
These are general dosage guidelines. Your doctor will determine the appropriate dose for your specific situation.
| Condition | Starting Dose | Maintenance Dose |
|---|---|---|
| Mild-to-moderate upper respiratory infection | 250 mg every 6 hours | 250–500 mg every 6 hours for 7–14 days |
| Skin and soft tissue infection | 250 mg every 6 hours | 500 mg every 6 hours for 7–10 days |
| Community-acquired pneumonia | 500 mg every 6 hours | 500 mg every 6 hours for 10–14 days |
| Acne vulgaris (topical) | Apply thin film twice daily | Continue twice daily; taper as tolerated |
Side Effects
Common Side Effects:
- Nausea and vomiting
- Abdominal cramping
- Diarrhea
- Metallic taste
- Anorexia
- Venous irritation (IV form)
Serious Side Effects:
- QT prolongation and arrhythmias
- Hepatotoxicity (cholestatic hepatitis)
- Clostridioides difficile-associated diarrhea
- Infantile hypertrophic pyloric stenosis
- Ototoxicity (high doses)
- Severe allergic reactions
Drug Interactions
Erythromycin is a potent inhibitor of CYP3A4 and can cause clinically significant interactions with numerous medications.
- Simvastatin / Lovastatin: Co-administration greatly increases statin levels, raising the risk of rhabdomyolysis. Suspend statin therapy during erythromycin treatment or switch to a non-interacting statin.
- Carbamazepine: Erythromycin inhibits carbamazepine metabolism, potentially causing toxicity (dizziness, ataxia, nausea). Monitor levels closely if used together.
- Warfarin: Erythromycin may enhance the anticoagulant effect of warfarin by inhibiting its hepatic metabolism. Monitor INR frequently and adjust warfarin dose as needed.
- Theophylline: Erythromycin reduces theophylline clearance, increasing the risk of theophylline toxicity (nausea, tremor, seizures). Monitor serum theophylline levels.
- QT-prolonging agents (e.g., amiodarone, sotalol, pimozide): Erythromycin itself prolongs the QT interval. Combining it with other QT-prolonging drugs significantly increases the risk of torsades de pointes. Avoid concurrent use when possible.
Additional Information
Erythromycin is a macrolide antibiotic used to treat various bacterial infections and as a prokinetic agent for gastrointestinal motility disorders. This versatile antibiotic has been in clinical use for decades and remains important for patients with penicillin allergies and for specific indications.
Mechanism of Action
Erythromycin exerts its antibacterial effect by binding to the 50S ribosomal subunit of susceptible bacteria, specifically to the 23S rRNA component. This binding blocks the translocation step of protein synthesis, preventing the growing polypeptide chain from moving from the A-site to the P-site of the ribosome. The effect is primarily bacteriostatic, though it can be bactericidal at high concentrations against highly susceptible organisms. Erythromycin also acts as a motilin receptor agonist in the gastrointestinal tract, stimulating gastric motility and accelerating gastric emptying through its prokinetic effects.
Available Formulations
Erythromycin is available in multiple formulations: erythromycin base (tablets, capsules), erythromycin stearate (tablets), erythromycin ethylsuccinate (oral suspension, tablets, chewable tablets), and erythromycin lactobionate (injection). Topical and ophthalmic formulations are also available. The base and stearate forms should be taken on an empty stomach, while ethylsuccinate can be taken with food to minimize GI upset.
Medical Uses
Erythromycin is FDA-approved for upper and lower respiratory tract infections (pneumonia, bronchitis, pertussis), skin and soft tissue infections, diphtheria, intestinal amebiasis, acute pelvic inflammatory disease (IV), syphilis in penicillin-allergic patients, Legionnaire's disease, chlamydial infections, and prophylaxis of rheumatic fever. Off-label uses include diabetic gastroparesis (prokinetic), acne vulgaris (topical), and ophthalmic infections. It remains important for patients allergic to penicillin.
Dosing Guidelines
For oral administration, typical adult doses range from 250-500 mg every 6 hours or 400-800 mg (ethylsuccinate) every 6-12 hours. For severe infections, up to 4 g daily may be used. For gastroparesis, 250 mg three times daily before meals is typical. Duration varies by indication. The base and stearate should be taken 1 hour before or 2 hours after meals; ethylsuccinate may be taken with food. Intravenous erythromycin is given by slow infusion due to venous irritation.
Important Safety Information
Erythromycin can cause QT prolongation and has been associated with potentially fatal cardiac arrhythmias, particularly torsades de pointes, especially when combined with other QT-prolonging drugs or in patients with electrolyte abnormalities. Hepatotoxicity, including cholestatic hepatitis, can occur, particularly with the estolate form. Infantile hypertrophic pyloric stenosis has been associated with erythromycin use in neonates. Clostridioides difficile-associated diarrhea may occur. The medication should be used with caution in patients with myasthenia gravis.
Drug Interactions
Erythromycin is a potent CYP3A4 inhibitor with numerous significant drug interactions. It increases levels of theophylline, carbamazepine, cyclosporine, tacrolimus, digoxin, midazolam, triazolam, lovastatin, simvastatin, and many others. Concurrent use with QT-prolonging drugs (Class IA and III antiarrhythmics, certain antipsychotics, fluoroquinolones) is contraindicated. Ergot derivatives are contraindicated due to ergotism risk. Colchicine toxicity can occur with concurrent use.
Special Populations
Erythromycin is pregnancy category B; it is one of the preferred macrolides during pregnancy when needed. The estolate form should be avoided in pregnancy due to hepatotoxicity risk. The medication is excreted in breast milk; use with caution during breastfeeding. Erythromycin has been associated with infantile hypertrophic pyloric stenosis when used in neonates under 2 weeks of age. Elderly patients may be more susceptible to QT prolongation and hepatotoxicity. No dose adjustment is needed for renal impairment. The medication is hepatically metabolized; use with caution in hepatic impairment.
Frequently Asked Questions
Questions to Ask Your Doctor
Consider discussing these topics at your next appointment:
- ✓Are there other antibiotics that might cause fewer stomach side effects for my type of infection?
- ✓Should any of my current medications be paused while I take erythromycin?
- ✓How will you know if erythromycin is working, and when should I follow up?
- ✓Is there a risk of antibiotic resistance if I have used macrolides before?
Medical Disclaimer: This information is for educational purposes only and should not be considered medical advice. Always consult with your healthcare provider before starting, stopping, or changing any medication. Your doctor can provide personalized recommendations based on your specific health condition and medical history.
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Questions About This Medication?
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