Dexamethasone + Gatifloxacin is a combination of two medicines: Dexamethasone + Gatifloxacin1 and Dexamethasone + Gatifloxacin2. Dexamethasone + Gatifloxacin1 is a steroid which blocks the production of certain chemical messengers (prostaglandins) that make the eye red swollen and itchy. Dexamethasone + Gatifloxacin2 is an antibiotic. It kills bacteria in the eye by preventing them from reproducing and repairing themselves. This treats your infection.