In vitro compatibility study of cephalosporin with intraocular irrigating solutions and intracameral medications

Background: To study the compatibility of cephalosporins with intraocular irrigating solutions and intracameral medications commonly used in cataract surgery. Design: The was an in vitro experiment conducted in the Research Laboratory of the Department of Microbiology, the Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong. Samples: Three cephalosporins – cefazolin, cefuroxime and ceftazidime – were separately diluted and mixed with irrigating solutions and intracameral medications to form 192 samples and 12 control solutions. Methods: The cephalosporins were dissolved in normal saline and further diluted to the concentration of 1 mg in 0.1 mL with normal saline, Ringer's solution, balanced salt solution and fortified balanced salt solutions. These were mixed with balanced salt solutions or fortified balanced salt solutions, with adrenaline, acetylcholine or carbachol and kept at 37°C for 2 h. The concentrations of free cephalosporins were measured with rapid high‐performance liquid chromatography at baseline (0 h) and at 2 h. Main Outcome Measures: Free concentrations of cephalosporins at 2 h were compared with mean baseline (0 h) value. A difference of 3 standard deviations or more was considered statistically significant. Results: At 2 h there was a significant drop in the cefuroxime concentration in preparations in which cefuroxime was diluted with normal saline (P < 0.01). In all preparations, the final concentrations of cephalosporins were higher than the minimal inhibitory concentrations (MIC₉₀) for microbials commonly isolated from the external eye. Conclusion: Cefazolin, cefuroxime and ceftazidime were compatible with irrigating solutions and intracameral medications commonly used in cataract surgery.