Eyeworld

43 EW FEATURE by Lauren Lipuma EyeWorld Staff Writer could revolutionize antibiotic ad- ministration in ophthalmic surgery. TriMoxi, a combination of moxiflox- acin and the steroid triamcinolone, and TriMoxiVanc, which also has vancomycin, are patent pending sin- gle use only formulations designed specifically for intraocular injection. Developed collaboratively by Imprimis, ophthalmologists, and pharmacists, TriMoxi and TriMoxiVanc are injected into the vitreous through the zonules using a cannula after placement of the IOL. This technique is superior to intra- cameral injection, Dr. Liegner said, because intraocular infections take hold in the vitreous, not the anterior chamber. "Inoculation with the infectious bacteria occurs during the procedure most likely from normal resident flo- ra, and becomes deposited into the vitreous as a consequence of fluid irrigation," he said. "The vitreous, a nutrient-rich protein matrix, not unlike an agar plate, invites rapid and successful growth of the bacteria, somewhat protected from the body's immune system due to intraocular privilege. Depositing the antibiotic into the vitreous directly attacks any wayward inoculation that might have occurred." In addition to stopping infec- tion at the source, the drugs also control postoperative inflammation and protect against surgery-induced cystoid macular edema. By combin- ing antibiotics and a steroid into one injection, 95% of patients no longer need postoperative eye drops, Dr. Liegner said. EW Editors' note: Dr. Henderson has finan- cial interests with Alcon. Dr. Liegner has financial interests with Imprimis Pharmaceuticals. Dr. Vasavada has financial interests with Alcon. Contact information Henderson: bahenderson@eyeboston.com Liegner: liegner@embarqmail.com Vasavada: icirc@abhayvasavada.com A fourth-generation fluoro- quinolone, 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 vancomy- cin 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 increasing- ly prevalent and aggressive MRSA. Cefuroxime, a second-genera- tion cephalosporin, has excellent gram-positive coverage, but only moderate gram-negative coverage. It is the most studied of the intra- camerals 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 3 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 stabil- ity after opening the vial. The com- pounding 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 Use of intracamerals remains controversial in the U.S. because there is no commercially available intraocular product approved by the Food and Drug Administration. To achieve the appropriate concentra- tion in the eye, antibiotics must be compounded by individual pharma- cies 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 compli- cations, including cystoid macular edema and toxic anterior segment syndrome. Many American physicians have surmounted the compounding barrier, however, and are using in- tracamerals 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 mini- mum inhibitory concentration, and a long half-life in the anterior chamber, said Abhay Vasavada, FRCS, Ahmedabad, India. The anti- biotic should be safe to the corneal endothelium and macula. In addi- tion, 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." Experienced surgeons discuss the benefits and drawbacks of available choices I ntracameral antibiotics are probably the most effective an- timicrobial approach other than topical povidone iodine, said Bonnie An Henderson, MD, Ophthalmic Consultants of Boston, and clinical professor, Tufts Uni- versity School of Medicine, Boston. Since the landmark ESCRS Endoph- thalmitis 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 antibiot- ics 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 accura- cy by the patient is suspect, it may be that many infections, though rare, were partly successful in their growth due to poor patient compli- ance with the prescribed and expen- sive topical medication," said Jeffrey Liegner, MD, Eye Care Northwest, Sparta, N.J. "Relieving the patient of this burden via direct intraocular delivery of antibiotics removes an important vulnerability." Which intracameral antibiotic is best? 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 first time. January 2015 Intracameral antibiotics

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