No Clinically Significant Drug Interactions Between Erythromycin Eye Ointment and Augmentin
There are no clinically significant drug interactions between erythromycin ophthalmic ointment and Augmentin (amoxicillin-clavulanate) when used together. These medications can be safely co-administered without dose adjustments or special monitoring.
Why This Combination is Safe
Minimal Systemic Absorption of Topical Erythromycin
Erythromycin ophthalmic ointment is applied topically to the eye surface and has negligible systemic absorption 1. The drug acts locally on the conjunctiva and cornea without reaching clinically meaningful blood concentrations. This is fundamentally different from oral or intravenous erythromycin, which does have documented drug interactions.
Augmentin's Drug Interaction Profile
The FDA label for Augmentin lists specific drug interactions to monitor 2:
- Probenecid: Increases amoxicillin blood levels (co-administration not recommended)
- Oral anticoagulants: May prolong prothrombin time/INR (requires monitoring)
- Allopurinol: Increases risk of rashes with ampicillin-class drugs
- Oral contraceptives: May reduce efficacy
Notably absent from this list is any mention of macrolide antibiotics like erythromycin, particularly topical formulations.
Important Context About Systemic Combinations
While topical erythromycin eye ointment poses no interaction risk, it's worth understanding that systemic combinations of beta-lactams and macrolides have shown antagonism in specific contexts:
- Research demonstrates that oral/IV erythromycin can antagonize penicillin's bactericidal activity against Streptococcus pneumoniae 3
- This antagonism occurs because bacteriostatic macrolides can interfere with bactericidal beta-lactam activity
- However, this is only relevant for systemic therapy of pneumococcal infections, not for topical ophthalmic use
Clinical Bottom Line
Proceed with both medications without concern. The ophthalmic route of erythromycin administration eliminates any potential for the drug-drug interactions seen with systemic macrolide therapy. Guidelines for treating various infections (conjunctivitis, blepharitis, skin infections) routinely include both topical erythromycin and oral amoxicillin-clavulanate in their treatment algorithms without warnings about concurrent use 4, 5, 6, 7, 5.
Common Pitfall to Avoid
Do not confuse topical ophthalmic erythromycin with oral erythromycin. The latter does have documented interactions with multiple medications due to CYP450 enzyme inhibition 8, 9, but these pharmacokinetic interactions require systemic drug exposure that simply doesn't occur with eye ointment.