Hello. The active ingredient in Optrex antibiotic eye drops is chloramphenicol antibiotic. This antibiotic is absorbed into the bloodstream in small amounts from eye application, but toxic effects via this route have only been reported following long-term exposure (i.e., use for much longer than a period of hours). The more probable side effects from your limited overuse may include: eye burning or stinging sensation; eyelid itching, redness, swelling, or rash. Rare side effects from this antibiotic (more likely with chronic use) include: sore throat and fever; anemia leading to pale skin or unusual fatigue or weakness; unusual bleeding or bruising. If you notice any side effects, stop the eye drops and contact the physician who prescribed the eye drops. If you have not experienced any side effects, then continue the antibiotic as originally prescribed.