What is a suitable oral antibiotic for a patient with bacterial conjunctivitis, assuming no significant allergies or comorbidities?

Oral Antibiotics Are NOT Recommended for Routine Bacterial Conjunctivitis

Bacterial conjunctivitis should be treated with topical antibiotics, not oral antibiotics, except in specific circumstances requiring systemic therapy (gonococcal, chlamydial, or severe cases with systemic involvement). 1, 2

Standard Treatment Approach

For uncomplicated bacterial conjunctivitis, the American Academy of Ophthalmology recommends a 5-7 day course of broad-spectrum topical antibiotic eye drops, not oral antibiotics. 1, 2

First-Line Topical Options (NOT Oral):

• Topical fluoroquinolones (moxifloxacin, levofloxacin, gatifloxacin, ciprofloxacin, besifloxacin) are effective against common pathogens including Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae 1
• Topical azithromycin 1.5% twice daily for 3 days is as effective as tobramycin 0.3% for 7 days, with better compliance due to shorter duration 3, 4, 5
• Other topical options include gentamicin, tetracycline, and ofloxacin 2

Why Topical Over Oral:

• Topical antibiotics provide higher local concentrations at the site of infection 6
• Topical therapy accelerates clinical and microbiological remission in days 2-5 of treatment 1, 2
• Reduces transmissibility and allows earlier return to school/work 2

When Oral Antibiotics ARE Indicated

Gonococcal Conjunctivitis (Requires Systemic Therapy):

• Ceftriaxone 250 mg IM single dose PLUS azithromycin 1 g oral single dose 1
• Topical therapy alone is insufficient as Neisseria gonorrhoeae can rapidly penetrate intact corneal epithelium 1
• Requires daily monitoring until resolution to prevent corneal perforation 1
• Must screen for concurrent genital infections and treat sexual partners 1

Chlamydial Conjunctivitis (Requires Systemic Therapy):

• Azithromycin 1 g oral single dose OR doxycycline 100 mg oral twice daily for 7 days 1
• Topical therapy alone is inadequate because Chlamydia trachomatis causes intracellular infection requiring systemic penetration 1
• More than 50% of infants with chlamydial conjunctivitis have infection at other sites, necessitating systemic treatment 1

Neonatal Conjunctivitis:

• Gonococcal: Ceftriaxone 25-50 mg/kg IV or IM single dose 1
• Chlamydial: Erythromycin base or ethylsuccinate 50 mg/kg/day oral divided into 4 doses for 14 days 1, 2

Critical Clinical Pitfalls

Do NOT Use Oral Antibiotics When:

• Patient has typical bacterial conjunctivitis with purulent discharge but no severe systemic features 1, 2
• Topical therapy has not been attempted first 2
• The diagnosis is viral conjunctivitis (antibiotics provide no benefit and promote resistance) 1

Red Flags Requiring Ophthalmology Referral:

• Visual loss, moderate or severe pain, severe purulent discharge 1, 2
• Corneal involvement or conjunctival scarring 1, 2
• Lack of response to therapy after 3-4 days 1, 2
• Suspected gonococcal or chlamydial infection (requires immediate referral) 1
• Neonatal conjunctivitis (requires immediate referral and systemic treatment coordinated with pediatrician) 1

Special Considerations:

• Contact lens wearers: Higher risk for Pseudomonas infection; use topical fluoroquinolones 2
• MRSA suspected: May require compounded topical vancomycin 1, 2
• Pregnancy: Avoid doxycycline or quinolones; use erythromycin or azithromycin for chlamydial coverage 1
• Children with gonococcal/chlamydial conjunctivitis: Consider sexual abuse 1, 2

Treatment Algorithm

1. Confirm bacterial conjunctivitis clinically (purulent discharge, conjunctival injection) 1, 2
2. Start topical broad-spectrum antibiotic for 5-7 days 1, 2
3. Obtain cultures and Gram stain if severe, not responding, or gonococcal/chlamydial suspected 1, 2
4. Add systemic antibiotics ONLY if gonococcal, chlamydial, or neonatal conjunctivitis confirmed 1, 2
5. Reassess in 3-4 days if no improvement 1, 2