What is the recommended antibiotic treatment and dosing for bacterial conjunctivitis in adults?

Management of Bacterial Conjunctivitis in Adults

For mild to moderate bacterial conjunctivitis in adults, a 5-7 day course of broad-spectrum topical antibiotic is recommended, with no particular antibiotic showing clear superiority over others. 1, 2

First-Line Treatment Options

Topical Antibiotics (5-7 day course):

• Fluoroquinolones:

  • Ofloxacin 0.3% - 1 drop in affected eye(s) every 4-6 hours 1
  • Moxifloxacin 0.5% - 1 drop in affected eye(s) 3 times daily 3
  • Levofloxacin 0.5% - 1 drop in affected eye(s) every 2 hours while awake for first 2 days, then every 4 hours for 3 more days 4

• Aminoglycosides:

  • Gentamicin 0.3% - 1 drop in affected eye(s) every 4 hours 1

• Other options:

  • Erythromycin 0.5% ointment - apply small amount (1/4 inch) to lower conjunctival sac 2-4 times daily 2
  • Polymyxin B-trimethoprim - 1 drop in affected eye(s) every 4 hours 3, 5

Azithromycin Option:

• Azithromycin 1% - 1 drop in affected eye(s) twice daily (8-12 hours apart) for first 2 days, then once daily for 5 more days 6

Treatment Algorithm

1. For mild bacterial conjunctivitis:

   • Select any broad-spectrum topical antibiotic listed above based on availability and cost
   • Instruct patient on proper administration technique
   • Continue for full 5-7 day course even if symptoms resolve earlier

2. For moderate to severe bacterial conjunctivitis:

   • Consider obtaining conjunctival cultures before initiating treatment
   • Begin with a fluoroquinolone (ofloxacin, moxifloxacin, or levofloxacin)
   • Follow up in 2-3 days to assess response
   • If no improvement, consider changing antibiotic based on culture results

3. For suspected MRSA conjunctivitis:

   • Consider obtaining cultures
   • May require compounded topical antibiotics such as vancomycin 1

Efficacy Considerations

Research shows that topical antibiotics provide faster clinical and microbiological resolution compared to placebo, particularly in the first 2-5 days of treatment 1. While bacterial conjunctivitis is often self-limiting in immunocompetent adults, treatment shortens the duration of symptoms and may reduce transmissibility 1, 2.

Comparative studies have shown:

• Moxifloxacin 0.5% three times daily achieved faster resolution (81% at 48 hours) compared to polymyxin B-trimethoprim four times daily (44% at 48 hours) 3
• Levofloxacin 0.5% showed superior microbial eradication rates (90%) compared to ofloxacin 0.3% (81%) 4

Follow-Up Recommendations

• For mild cases: Follow-up only if symptoms persist beyond 3-4 days of treatment
• For moderate to severe cases: Follow-up within 2-3 days to assess response
• At follow-up visits, assess:
  • Resolution of symptoms
  • Visual acuity
  • Slit-lamp examination if available

Important Caveats

1. Complete the full course of treatment to prevent recurrence and antibiotic resistance 6

2. Special cases requiring systemic antibiotics:

   • Gonococcal conjunctivitis
   • Chlamydial conjunctivitis
   • Conjunctivitis with significant eyelid involvement

3. Warning signs requiring urgent referral:

   • Corneal involvement
   • Severe pain
   • Vision loss
   • No improvement after 3-4 days of treatment

4. Adjunctive measures:

   • Warm compresses for eyelid involvement
   • Good hand hygiene to prevent transmission
   • Avoid sharing towels/washcloths

5. Return to work/school: Patients can typically return to work/school after 24 hours of antibiotic treatment if symptoms are improving 2