This literature review compares the efficacy of 3 most commonly employed endophthalmitis prophylaxis intracameral antibiotics: cefuroxime, vancomycin and moxifloxacin
Study design
The authors conducted a literature review of prophylactic antibiotic literature. They developed a mathematical model to compare the efficacy of moxifloxacin, cefuroxime and vancomycin against the most common causes of postoperative endophthalmitis such as methicillin-resistant coagulase-negative Staphylococcus (MRCoNS), methicillin-sensitive coagulase-negative Staphylococcus (MSCoNS), methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA). For the mathematical modeling portion of the study, they used a moxifloxacin concentration of 600 ug/0.4 mL, and cefuroxime and vancomycin concentrations of 1.0 mg/0.1 mL.
Outcomes
The authors generated 3 key figures showing the calculated expected abatement rate for each antibiotic.
The level of moxifloxacin in the anterior chamber exceeded estimates from the ARMOR study, with a minimum inhibitory concentration required to inhibit the growth of 90% of organisms (MIC90) of 37 hours for MSSA, 10.5 hours for MRSA and 7.5 hours for CoNS. The difference between the anterior chamber concentration and the target MIC was greater with moxifloxacin than cefuroxime or vancomycin. In addition, the analysis revealed that the concentration of moxifloxacin remains above the MIC90 of MSSA for 40 hours, whereas the concentrations of cefuroxime and vancomycin remain above the MIC90 of CoNS for only 21 hours.
Limitations
The authors made several key assumptions to facilitate mathematical modeling of the antibiotic abatement profiles. They assumed that the clearance rates from the anterior chamber of all 3 antibiotics (moxifloxacin, vancomycin, and cefuroxime) were similar. Another assumption was that the primary cause of concentration decline was the effect of dilution from aqueous secretion at a rate of 2.0 uL/min, that the newly pseudophakic aqueous volume was 500 uL, and that the concentration of the antibiotic in the anterior chamber declined to one-fourth of the initial concentration over the first hour after cataract surgery (based on accepted pharmacokinetic standards). Based on these assumptions, they calculated that the half-life of all 3 antibiotics in the anterior chamber was 2.89 hours.
Clinical significance
The authors developed a mathematical model of the abatement profiles of cefuroxime, vancomycin and moxifloxacin—the 3 most commonly used antibiotics used (all off-label) intracamerally by cataract surgeons to prevent postoperative endophthalmitis. Their model can be used to compare the duration of bactericidal activity of these antibiotics against the most common pathogens known to cause postoperative endophthalmitis.
The authors draw an important conceptual distinction between dose-dependent antibiotics (e.g., moxifloxacin) and time-dependent antibiotics (e.g., cefuroxime and vancomycin). They found that intracameral moxifloxacin achieves highly concentrated and sustained levels sufficient to inhibit growth of the most common bacteria that cause postoperative endophthalmitis, more so than cefuroxime or vancomycin. This study contributes to the growing literature in support of using intracameral moxifloxacin for the prevention of postoperative endophthalmitis.