What is the proper dosage and administration of erythromycin (antibiotic ointment) for a patient with conjunctivitis or a skin infection like impetigo?

Erythromycin Ointment Dosing and Administration

For bacterial conjunctivitis, apply erythromycin ophthalmic ointment 2-3 times daily for 5-7 days; for impetigo and superficial skin infections, apply erythromycin ointment to affected lesions twice daily for 7-10 days, though mupirocin or retapamulin are preferred first-line topical agents due to superior efficacy and lower resistance rates. 1, 2

Ophthalmic Use for Conjunctivitis

Standard Bacterial Conjunctivitis

• Apply erythromycin ophthalmic ointment 2-3 times daily for uncomplicated bacterial conjunctivitis 1
• A 5-7 day course is typically sufficient for resolution 1
• Topical erythromycin alone is inadequate for chlamydial or gonococcal conjunctivitis, which require systemic antibiotics 1, 3

Neonatal Chlamydial Conjunctivitis

• Topical erythromycin ointment is ineffective for treating neonatal chlamydial conjunctivitis—systemic oral therapy is mandatory 1
• Administer erythromycin base or ethylsuccinate 50 mg/kg/day orally divided into 4 doses for 14 days 1
• Treatment efficacy is approximately 80%; a second course may be required if infection persists 1
• Topical ointment does not prevent perinatal chlamydial transmission from mother to infant 4

Special Ophthalmic Applications

• For blepharitis, apply erythromycin ointment to eyelid margins once or more times daily (or at bedtime) for several weeks, with duration guided by severity and treatment response 1
• For eyelid lice infestation, apply erythromycin ophthalmic ointment 2-3 times daily for 10 days to smother adult lice and nits, combined with mechanical removal using forceps 1

Critical Ophthalmic Caveats

• Erythromycin ointment should not be used as primary therapy for bacterial keratitis due to inadequate corneal penetration; fluoroquinolones are required 3
• For gonococcal conjunctivitis, systemic ceftriaxone (not erythromycin) is mandatory 1, 3
• Methicillin-resistant S. aureus conjunctivitis may require compounded topical vancomycin rather than erythromycin 1

Dermatologic Use for Skin Infections

Impetigo and Superficial Skin Infections

• Apply erythromycin ointment to affected lesions twice daily for 7-10 days, depending on clinical response 2
• Topical erythromycin is reserved for patients with limited, localized lesions only—not appropriate for extensive or systemic infections 2

Important Limitations for Skin Use

• Mupirocin or retapamulin ointments are generally preferred over erythromycin for topical treatment of impetigo due to better efficacy and lower resistance rates 2
• Resistance is a significant concern, as many strains of Staphylococcus aureus and Streptococcus pyogenes are resistant to erythromycin 2
• Oral antibiotics (erythromycin or flucloxacillin) are superior to topical therapy for more extensive impetigo, especially in high-transmission settings or when nephritogenic strains are present 5

Pregnancy Considerations

• Erythromycin base or ethylsuccinate are safe alternatives for pregnant women with chlamydial infections 4, 1
• Recommended regimens: Erythromycin base 500 mg orally four times daily for 7 days OR 250 mg orally four times daily for 14 days 4
• Alternative: Erythromycin ethylsuccinate 800 mg orally four times daily for 7 days OR 400 mg orally four times daily for 14 days 4
• Erythromycin estolate is contraindicated during pregnancy due to drug-related hepatotoxicity 4
• The lower dose 14-day regimens may be considered if gastrointestinal tolerance is a concern 4

Common Pitfalls to Avoid

• Do not use topical erythromycin alone for chlamydial conjunctivitis—oral therapy is required to eradicate nasopharyngeal colonization 6
• Sexual contacts of patients with chlamydial or gonococcal conjunctivitis require treatment to prevent reinfection 1
• Retesting approximately 3 months after treatment is recommended to ensure clearance 1
• In cases of co-infection with both gonorrhea and chlamydia, treat both pathogens simultaneously 1
• Avoid prolonged topical use beyond 10 days, as this can cause medication toxicity and corneal epithelial damage 3