January 2015

 

COVER FEATURE

 

Intracameral antibiotics

Which intracameral antibiotic is best?


by Lauren Lipuma EyeWorld Staff Writer

 
   

Experienced surgeons discuss the benefits and drawbacks of available choices

Intracameral 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 Groups 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, N.J. 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 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 (Alcons 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 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 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. 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 intracameral 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 flora, 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 bodys 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 infection at the source, the drugs also control postoperative inflammation and protect against surgery-induced cystoid macular edema. By combining antibiotics and a steroid into one injection, 95% of patients no longer need postoperative eye drops, Dr. Liegner said.

Editors note: Dr. Henderson has financial 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

Which intracameral antibiotic is best? Which intracameral antibiotic is best?
Ophthalmology News - EyeWorld Magazine
283 110
220 227
,
2017-04-13T05:36:06Z
True, 1