Drug Topics- August 11, 2008

2 HSE DRUG TOPICS AUGUST 11, 2008 www.drugtopics.com > > > Clinical Practice Vancomycin no longer ‘old dependable’ against MRSA, roundtable warns Naomi Pfeiffer he evolution of methicillin-resistant Staphylococus aureus (MRSA) has led to the reduced efficacy of vancomycin therapy. “In my experience, vancomycin is no longer a reliable therapeutic choice for patients with serious S. aureus infections,” Stan Deresinski, M.D., clinical professor of medicine, Stanford University, said in New York at a Cubist Pharmaceuticals-sponsored roundtable of infectious disease experts. MRSA, the so-called “ superbug” because of its drug-resistance, was originally seen only in hospitalized Alan Tice, M.D. patients with compromised immune University of Hawaii systems. Later it became prevalent in the community. Today new and different strains of MRSA, genetically distinct from early varieties and often more virulent, are again appearing beyond the hospital. According to the Centers for Disease Control and Prevention, MRSA killed 18,650 Americans in 2005— more than the 16,865 due to AIDS. Additionally, MRSA now accounts for some two-thirds of skin infections in emergency rooms, up from 2% 35 years ago. “Outbreaks of resistant and potentially deadly bacterial infections caused by MRSA are occurring at worrisome rates both inside and outside hospitals,” panelist Alan Tice, M.D., infectious disease specialist and associate professor at the John A. Burns School of Medicine at the University of Hawaii, said. New York has received 676 MRSA reports since February, Tice said. “But these cases probably represent only the tip of the iceberg since just 21 labs out of 49 have T “These cases probably represent only the tip of the iceberg” been reporting.” Around 4,000 cases are likely more accurate, he added. Michael Rybak, Pharm.D., MPH, Wayne State University, said, “Compared to the multidrug resistance often seen in hospital-acquired MRSA strains, most community-associated (CA)-MRSA isolates remain susceptible to tetracyclines, clindamycin, and trimethoprim-sulfamethoxazole (TMP-SMZ ).” Deresinski added the following to his list of antibiotics to which varieties of MRSA remain vulnerable: • Quinupristin/dalfopristin: “This combination is bactericidal against S. aureus but only bacteriostatic against other pathogens,” he said. In one randomized trial comparing the daily combination with vancomycin, patients with hospital-acquired MRSA pneumonia who had received the daily combination had a clinical response rate of 19.4% compared with 40% in vancomycin recipients. • Linezolid: In a randomized open-label trial comparing linezolid and vancomycin, the two agents yielded similar results in hospitalized patients with MRSA infections. Additionally, another comparator trial suggested that linezolid is superior to vancomycin as a treatment for hospital-acquired pneumonia due to MRSA. • Daptomycin: Deresinski described the recently approved agent as a “novel lipopeptide antibiotic with bactericidal activity against S. aureus that binds to the bacterial cell membrane, disrupting membrane potential.” At the same time, daptomycin is ineffective in treating pneumonia, he said. • Fluoroquinolones: While most CA-MRSA strains are susceptible to fluoroquinolones, this is not true for all MRSA strains, Deresinksi said. THE AUTHOR is a writer based in New York. http://www.drugtopics.com

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Drug Topics- August 11, 2008 Contents Latebreakers Letters DEA Proposes Rule To Allow Electronic Prescriptions for Controlled Substances Merger, Medicare Reform Could Mean Broader E-Prescribing Adoption New Combination Pill Approved for Type 2 Diabetes New Eczema Guildlines Promote Use of Emollients, Then Topical Corticosteroids Agencies Flush Original Strategies in Favor of Promoting Drug Take-Back Programs JP at Large: You Laughing at Me? Pharmacists Find Themselves at Mercy of Prior Authorization State Law Requiring PBM Transparency See Some Gains, Some Losses Global Counterfeiting Still Growing, Says U.S. Commerce Official FDA Saftey Page: Prophylthiouracil Still Confused with Purinethol (mercaptopurine) New Products Bring Lice Treatment to a Head NACDS Marketplace Showcases New Product that Fill Unmet Needs Update on Respiratory Tract Infections Execs Share War Stories About Adopting Technology in their Stores New Products Advertisters Index Classified Viewpoint: Medicare Part D Revisions sorely needed

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