1. Introduction
Erythromycin is a macrolide antibiotic used to treat various bacterial infections. It inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit, making it effective against gram-positive and some gram-negative bacteria. Erythromycin also has prokinetic properties, which make it useful in specific gastrointestinal disorders.
2. Indications
- Approved Indications:
- Respiratory tract infections (e.g., pneumonia, bronchitis, pharyngitis).
- Skin and soft tissue infections (e.g., cellulitis, impetigo).
- Sexually transmitted infections (e.g., chlamydia, syphilis).
- Whooping cough (pertussis).
- Eye infections (e.g., conjunctivitis in neonates).
- Off-Label Uses:
- Gastroparesis (due to its prokinetic effects).
- Acne vulgaris (topical use).
3. Dosage
- Adults:
- Infections: 250–500 mg orally every 6–12 hours (maximum: 4 g/day).
- Gastroparesis: 125–250 mg orally three times daily before meals.
- Children:
- Infections: 30–50 mg/kg/day in divided doses every 6–8 hours.
- Neonatal conjunctivitis: 50 mg/kg/day in divided doses every 6–12 hours.
- Elderly:
- No specific dose adjustment required, but monitor for gastrointestinal and cardiac side effects.
4. Administration
- Oral forms: Take with or without food. If gastrointestinal upset occurs, take with food.
- Extended-release tablets: Swallow whole, do not crush or chew.
- IV infusion: Administer slowly to avoid vein irritation.
- Topical and ophthalmic forms: Apply as directed by a healthcare provider.
5. Forms Available
- Tablets: 250 mg, 500 mg.
- Capsules: 250 mg, 500 mg.
- Oral suspension: 200 mg/5 mL, 400 mg/5 mL.
- Intravenous solution: 50 mg/mL.
- Topical gel: 2%.
- Ophthalmic ointment: 0.5%.
6. Side Effects
6.1. Common Side Effects
- Nausea and vomiting.
- Diarrhoea.
- Abdominal pain or cramping.
6.2. Less Common Side Effects
- Skin rash.
- Loss of appetite.
- Dizziness.
6.3. Rare but Serious Side Effects
- Prolonged QT interval and arrhythmias (e.g., torsades de pointes).
- Cholestatic hepatitis.
- Severe allergic reactions (e.g., anaphylaxis).
7. Warnings
- QT Prolongation: Increased risk of torsades de pointes, especially in patients with pre-existing cardiac conditions or when used with other QT-prolonging drugs.
- Hepatotoxicity: Use cautiously in patients with liver impairment, as erythromycin may cause cholestatic hepatitis.
- Clostridioides difficile-Associated Diarrhoea (CDAD): May occur during or after treatment; report persistent diarrhoea to a healthcare provider.
8. Precautions
- Avoid use in patients with a history of macrolide allergy.
- Use with caution in patients with myasthenia gravis, as it may worsen symptoms.
- Monitor for drug interactions, as erythromycin is a strong inhibitor of CYP3A4.
9. Interactions
- Drug-Drug Interactions:
- CYP3A4 substrates (e.g., warfarin, simvastatin, midazolam): Increased plasma levels and toxicity.
- QT-prolonging drugs (e.g., amiodarone, sotalol): Increased risk of arrhythmias.
- Theophylline: Increased levels and toxicity.
- Antacids: May reduce erythromycin absorption.
- Drug-Food Interactions:
- Absorption may be reduced by grapefruit juice.
10. Monitoring Parameters
- Monitor for symptom improvement in infections.
- Assess for gastrointestinal side effects, particularly diarrhoea.
- Monitor ECG in patients at risk of QT prolongation.
- Check liver function tests in long-term therapy or in patients with pre-existing liver conditions.
11. Use in Children
- Safe and widely used in paediatric populations for infections and neonatal eye prophylaxis. Adjust doses based on weight.
12. Use in Pregnancy
- Category B: Considered safe for use during pregnancy. Often used for chlamydia or syphilis in pregnant women.
13. Use in Elderly
- Safe for use, but elderly patients are more prone to cardiac side effects, such as QT prolongation.
14. Use in Kidney Disease
- No dose adjustment is required in renal impairment.
15. Use in Liver Disease
- Use cautiously, as erythromycin is metabolised in the liver. Monitor liver function during therapy.
16. Patient Counselling Points
- Take erythromycin as prescribed, completing the full course even if symptoms improve.
- Report any signs of severe diarrhoea, abdominal pain, or unusual fatigue to your doctor.
- Avoid grapefruit juice during treatment.
- If prescribed for acne or rosacea, it may take several weeks to see improvement.
- For topical or eye formulations, apply only as directed, and avoid contaminating the tip of the tube or bottle.
17. Table of Brand Names, Manufacturers, and Prices
Brand Name | Manufacturer | Price (USD) |
---|---|---|
Erythrocin | Abbott | $20–40 (30 tablets, 250 mg) |
EES (Erythromycin Ethylsuccinate) | Pfizer | $25–50 (30 tablets, 400 mg) |
Generic Erythromycin | Various | $10–30 (30 tablets, 250 mg) |
18. FAQs (15 Questions)
- What is erythromycin used for?
It is used to treat bacterial infections such as respiratory infections, skin infections, and sexually transmitted infections. - How does erythromycin work?
It inhibits bacterial protein synthesis, preventing bacterial growth. - What are the common side effects of erythromycin?
Nausea, vomiting, diarrhoea, and abdominal cramps are common side effects. - Can erythromycin cause heart problems?
Yes, it can prolong the QT interval, increasing the risk of arrhythmias, especially in patients with pre-existing cardiac conditions. - Can erythromycin be used in children?
Yes, it is safe and effective for paediatric use, with doses adjusted based on weight. - Can erythromycin be taken during pregnancy?
Yes, it is considered safe during pregnancy (Category B). - What should I do if I miss a dose of erythromycin?
Take it as soon as you remember, but skip it if it’s close to the next dose. Do not double up. - Does erythromycin interact with other medications?
Yes, it interacts with CYP3A4 substrates, QT-prolonging drugs, and antacids. - Can erythromycin be used for acne?
Yes, it is used topically or orally for acne, though treatment may take several weeks. - Is erythromycin effective against all bacterial infections?
No, it is ineffective against resistant strains or certain gram-negative bacteria. - Can erythromycin cause diarrhoea?
Yes, it may cause diarrhoea, including serious conditions like Clostridioides difficile-associated diarrhoea. - How should erythromycin be stored?
Store at room temperature, away from light and moisture. - Can I drink alcohol while taking erythromycin?
Moderate alcohol consumption is generally safe, but excessive alcohol may worsen side effects. - How long does it take for erythromycin to work?
Symptom improvement is typically seen within a few days, but the full course should be completed. - Can erythromycin cause liver problems?
Rarely, it can cause cholestatic hepatitis, especially with prolonged use.