EyeWorld Asia-Pacific March 2015 Issue

March 2015 14 EWAP FEATURE Which intracameral antibiotic is best? by Lauren Lipuma EyeWorld Staff Writer Experienced surgeons discuss the benefits and drawbacks of available choices I ntracameral antibiotics are probably the most effective antimicrobial approach other than topical povidone iodine, said Bonnie An Henderson, MD , Ophthalmic Consultants of Boston, and clinical professor, Tufts University School of Medicine, Boston. Since the landmark ESCRS Endophthalmitis Study Group’s study was published in 2006 demonstrating the effectiveness of intracameral cefuroxime in lowering rates of infection post cataract surgery, a number of peer-reviewed articles have shown that intracamerals are more effective than topical antibiotics at preventing endophthalmitis. The effectiveness of antibiotic injection over topical drops could be due to the fact that it eliminates the issue of compliance. “Since eye drop use and accuracy by the patient is suspect, it may be that many infections, though rare, were partly successful in their growth due to poor patient compliance with the prescribed and expensive topical medication,” said Jeffrey Liegner, MD , Eye Care Northwest, Sparta, NJ. “Relieving the patient of this burden via direct intraocular delivery of antibiotics removes an important vulnerability.” Use of intracamerals remains controversial in the U.S. because there is no commercially available intraocular product approved by the U.S. Food and Drug Administration. To achieve the appropriate concentration in the eye, antibiotics must be compounded by individual pharmacies or self-mixed by the physician in the operating room. This has proven to be a large barrier for many physicians as concentration errors can result in a variety of complications, including cystoid macular edema and toxic anterior segment syndrome. Many American physicians have surmounted the compounding barrier, however, and are using intracamerals regularly. Moxifloxacin, vancomycin, and cefuroxime have emerged as the top choices among anterior segment surgeons, but two new drug formulations that became available this year are resolving the compounding issues and paving the way for completely dropless cataract surgery to become a reality. Vigamox, cefuroxime, vancomycin The ideal intracameral antibiotic should have a broad spectrum of antibacterial coverage, a low minimum inhibitory concentration, and a long half- life in the anterior chamber, said Abhay Vasavada, FRCS , Ahmedabad, India. The antibiotic should be safe to the corneal endothelium and macula. In addition, it should be easy to formulate. With these criteria in mind, Dr. Vasavada thinks the best choice is Vigamox (moxifloxacin, Alcon, Fort Worth, Texas). “Vigamox, being preservative free, allows direct injection inside the eye. There is no reconstitution required, therefore errors due to incorrect concentration/dosing are avoided,” he said. “It also allows the same antibiotic to be used preoperatively, intraoperatively, and postoperatively.” A fourth-generation fluoroquinolone, Vigamox has broad-spectrum protection and is well tolerated in the eye. The drawback of Vigamox is cost; there are no generics available (Alcon’s first patent will expire in 2019), and it is specifically labeled for topical use only. Dr. Henderson uses vancomycin in her practice, but would prefer Vigamox if cost were not an issue. Vancomycin has coverage only against gram-positive bacteria, but is incredibly effective against these pathogens, including the increasingly prevalent and aggressive MRSA. Cefuroxime, a second- generation cephalosporin, has excellent gram-positive coverage, but only moderate gram-negative coverage. It is the most studied of the intracamerals but requires a two-step compounding process, leaving more room for error. Vancomycin and cefuroxime are excellent choices, but each vial is “single use only,” forcing the surgeon to discard the remaining unused portion, Dr. Liegner said. Not only does this waste valuable antibiotic, but also has the potential to create “superbugs” by contaminating the water table with antibiotics. Of the three options, Dr. Liegner thinks that vancomycin is the best for American surgeons. “The primary threat of infection is from gram-positive bacteria, and this is the king of antibiotics against gram positives, with a proven intraocular track record of safety and efficacy,” he said. The problem, however, is the single use issue and drug stability after opening the vial. The compounding pharmacies are able to produce single dose sizes, Dr. Liegner said, but many do not have proper intraocular formulation protocols for safety. The dropless cataract surgery revolution Imprimis Pharmaceuticals (San Diego) introduced 2 compounded drug formulations in 2014 that could revolutionize antibiotic administration in ophthalmic surgery. TriMoxi, a combination of moxifloxacin and the steroid triamcinolone, and TriMoxiVanc, which also has vancomycin, are patent pending single use only formulations designed specifically for intraocular injection. AT A GLANCE • Compounding is a large barrier to adopting intracameral use. • Vancomycin is the most effective antibiotic for gram-positive infections such as MRSA. • New formulations available this year combine antibiotics and a steroid into a single injection, making dropless cataract surgery possible for the rst time.