New Study Cites Benefits Of Ertapenem For Diabetic Foot Infections

By Brian McCurdy, Associate Editor

   In the past, the majority of comparative studies of antibiotics for diabetic foot infections have been relegated to smaller, unblinded trials. However, a new randomized, multicenter study of over 500 patients found that the simpler dosing regimen of ertapenem (Invanz, Merck) had comparable results to piperacillin/tazobactam in treating these infections.    In what study co-author David G. Armstrong, DPM, MSc, PhD, calls “easily the largest ever randomized controlled trial of diabetic foot infections,” the double-blinded SIDESTEP Study of Diabetic Foot Infections found that patients treated with once-a-day dosing of ertapenem had similar clinical and microbiological outcomes with those who were treated with piperacillin/tazobactam every six hours.    Data from the study, which was recently presented at the 44th Interscience Conference on Antimicrobial Agents and Chemotherapy, will also be presented as an abstract at the upcoming Symposium on Advanced Wound Care in April.    Patients in the study received either 1 g/d of ertapenem or 3.375 g qid of piperacillin/tazobactam. According to the study protocol, the patients remained on IV for five days but could subsequently be switched to oral amoxicillin/clavulanate for a total treatment period of 28 days.    At the end of IV therapy, ertapenem had a success rate of 94.3 percent (+/- 3 percent) while piperacillin/tazobactam had a success rate of 92.3 percent (+/- 3.5 percent). The study authors also observed similar clinical success rates at the 10-day follow-up visit as ertapenem had a 87.7 percent success rate and piperacillin/tazobactam had a 82.8 percent success rate.

Assessing The Advantages Of Ertapenem

   Both Dr. Armstrong and Benjamin A. Lipsky, MD, FACP, the lead author of the study, cite ertapenem as a useful empiric agent, given its broad spectrum of activity and its once-a-day parenteral dosing.    With the exception of methicillin resistant staphylococci, ertapenem covers “most of the aerobic gram-positive cocci that are the primary pathogens in diabetic foot infections,” explains Dr. Lipsky, a Professor of Medicine at the University of Washington and the Director of the General Internal Medicine Clinic with the VA Puget Sound Health Care System in Seattle.    Dr. Lipsky, a Fellow of the Infectious Diseases Society of America, says ertapenem is also effective against aerobic gram-negative rods and obligate anaerobes that are often part of mixed infections in chronic or previously treated infections. He also notes that ertapenem has a bactericidal action and “good penetration to infected soft tissues.”    As far as drawbacks go for ertapenem, Dr. Lipsky concedes the drug does not cover Pseudomonas or some other non-fermentative gram-negative rods. However, he notes these are “not usually primary pathogens in diabetic foot infections.”

What Impact Will The Study Have?

   Dr. Armstrong, a member of the National Board of Directors of the American Diabetes Association, expressed enthusiasm about the potential application of the study results.     “I believe the myriad of data we will have to pore through will yield a treasure trove of information that will ultimately help us better treat this most high risk patient population,” says Dr. Armstrong, a Professor of Surgery, Chair of Research and Assistant Dean at the Dr. William M. Scholl College of Podiatric Medicine at the Rosalind Franklin University of Medicine. Editor’s Note: The Symposium on Advanced Wound Care will be held from April 21 to 24 in San Diego, Calif. For more information, go to For related articles on diabetic foot infections, see the supplement “Treating MRSA Infections” at

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