Ocular penetration of topical antibiotics: study on the penetration of chloramphenicol, tobramycin and netilmicin into the anterior chamber after topical administration

Abstract Background To compare penetration in the aqueous humour of topically applied antibiotics. Design Randomized prospective study, D epartment of O phthalmology, U niversity of P erugia, I taly Participants Patients undergoing cataract surgery. Methods One hundred twenty‐two patients were included: 14 received one drop of chloramphenicol suspension; 12 one application of chloramphenicol gel; 11 one drop of netilmicin suspension; 13 one drop of tobramycin suspension; 37 repeated instillations of chloramphenicol suspension every 10 min for a total of four drops; and 35 repeated instillations of chloramphenicol gel every 10 min for a total of four drops. Samples were taken immediately before surgery from the anterior chamber in order to determine the antibiotic by means of high‐performance liquid chromatography. Samples were taken 45–190 min after the eye drops were instilled. Main Outcome Measures Intraocular penetration of chloramphenicol, netilmicin and tobramicyn. Results After a single administration, netilmicin and tobramycin were undetectable, whereas the chloramphenicol suspension reached a mean concentration of 0.23 ± 0.21 μg/mL, and the chloramphenicol gel a mean concentration of 0.13 ± 0.14 μg/mL. After repeated administrations, the mean concentrations of the chloramphenicol suspension and gel were 0.60 ± 0.26 μg/mL and 0.58 ± 0.18 μg/mL, respectively. Conclusions Tobramycin and netilmicin do not reach detectable concentrations, whereas chloramphenicol, after multiple administrations, reaches concentrations that are effective against H aemophilus influenzae and H aemophilus parainfluenzae , L egionella pneumophila , M oraxella catarrhalis , N eisseria meningitidis , P asteurella multocida and S treptococcus pneumoniae . This means that chloramphenicol can be rationally used in the prophylaxis and treatment of infections supported by sensitive germs.