The best-known topical antibiotic is chloramphenicol (Figure 1); it is sometimes even well known to patients, especially contact lens wearers, which is not always a good thing.
Chloramphenicol is bacteriostatic; it is effective against a wide range of bacteria and is normally the first-line treatment for simple acute bacterial conjunctivitis. (1) It’s the one your GP or pharmacist will immediately think of and is available as drops or ointment. In a minor eye conditions service (MECS) therapeutics audit in Greater Manchester, chloramphenicol was stipulated by written order 90.2 per cent of the time when an antibiotic was thought appropriate; fusidic acid was chosen 9.8 per cent of the time. (2)
As well as being prescribed for active simple acute bacterial conjunctivitis, chloramphenicol is commonly supplied for prophylaxis following ocular surgery or trauma. The typical dosage for bacterial conjunctivitis is four times per day, although for severe cases it may start as one drop every two to four hours, to be continued for 48 hours after resolution. Dosage varies with particular cases, and any infection not responding within two days should be re-evaluated.