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Quicker Response Seen in Patients With MRSA Who Were Treated With Linezolid vs. Vancomycin

New York, June 1, 2005 – Pfizer's antibiotic ZYVOX (linezolid injection, tablets, and for oral suspension) is more effective than vancomycin for the treatment of complicated skin and soft tissue infections (cSSTIs) caused by methicillin-resistant Staphylococcus aureus (MRSA), according to the largest MRSA cSSTIs study to date published in Antimicrobial Agents and Chemotherapy. Of the total study population, including those treated for methicillin-susceptible infections, the number of patients cured with ZYVOX was comparable to those cured with vancomycin. In addition, patients taking ZYVOX spent up to five fewer days on IV treatment because of its availability as a pill. Available in interchangeable IV and oral formulations, ZYVOX is the only oral medicine approved by the U.S. Food and Drug Administration for MRSA infections.

This study involved 1,180 patients with cSSTIs, 361 of whom had confirmed MRSA infections. MRSA is a serious, multidrug-resistant infection, which is on the rise and can lead to prolonged hospitalization, along with increased morbidity, mortality and cost. Patients in the microbiologically evaluable MRSA subgroup treated with ZYVOX had better microbiologic cure rates: 88.6 percent for ZYVOX patients vs. 66.9 percent for vancomycin patients.

"In this study, ZYVOX was shown to be better than traditional vancomycin therapy in improving outcomes for patients with serious MRSA infections," said Dr. John Weigelt, lead investigator of the study, and professor and vice chairman of the department of surgery at the Medical College of Wisconsin. "These data also reinforce the value of having a pill for patients which may allow patients to leave the hospital sooner on oral therapy."

Because of the oral availability of ZYVOX, patients in the ZYVOX arm had up to five fewer days on IV therapy than patients treated with vancomycin. More than half of study participants (52 percent) treated with ZYVOX began treatment on the oral formulation. The U.S. Centers for Disease Control and Prevention recommends getting the catheters out and using an IV only when essential since these and other invasive devices are a frequent cause of hospital-acquired infections.

Skin and soft tissue infections are a common cause of morbidity in the community and hospital. Those at risk for cSSTIs include surgical patients, patients with diabetes and those who are immunocompromised, such as patients with cancer. These infections are increasingly caused by resistant bacteria such as MRSA. According to a previous study, the rate of MRSA among cSSTI isolates is approximately 30 percent. Thirty years ago, only two percent of hospital-acquired Staph infections in intensive care units were resistant to antibiotics, but today physicians are seeing rates of approximately 60 percent.

"The rapid emergence of MRSA is an increasing public health problem, especially among hospitalized patients where skin and soft tissue infections caused by MRSA can be fatal," said Dr. Weigelt. "ZYVOX has been shown to have excellent skin and tissue penetration which I believe is important when treating complicated SSTIs to ensure the treatment reaches the infection site. ZYVOX is a critical option for patients with risk factors for MRSA, such as an acute illness, a compromised immune system or previous antibiotic use."

Study Results
In the intent-to-treat (ITT) population, ZYVOX had clinical cure rates of 92.2 percent vs. 88.5 percent for patients on vancomycin. In the MRSA subgroup (microbiologically evaluable population), patients treated with ZYVOX had better microbiologic cure rates of 88.6 percent compared with 66.9 percent for patients on vancomycin. In the ITT population, patients in the ZYVOX group had fewer days of IV therapy than those in the vancomycin group (4.0 + 2.6 days vs. 9.0 + 5.3 days, respectively). The overall mean treatment duration was significantly longer in the ZYVOX group vs. the vancomycin group (11.8 + 4.9 days vs. 10.9 + 5.3, respectively).

Study Background
This randomized, open-label, comparator-controlled, multicenter, multinational study evaluated 1,180 patients' response to treatment with ZYVOX and vancomycin. The most common types of cSSTIs seen in study patients were cellulitis (spreading infection of the skin and subcutaneous tissues), a major skin abscess (pus and infected material build up in the skin) and an infected surgical incision. Clinical efficacy outcomes (e.g., cured, failed or indeterminate) were measured by resolution of the signs and symptoms of infection compared with baseline. Microbiologic cure rates were defined as presumed or documented eradication. The study also compared the mean IV duration of each treatment and the total number of days that patients received antibiotic therapy. Patients who received vancomycin did not have the option to start on or switch to an oral agent because vancomycin is only available intravenously.

Patients were randomly assigned in a 1:1 ratio to receive either IV or oral ZYVOX 600 mg every 12 hours (592 patients) or IV vancomycin 1 g every 12 hours (588 patients) for seven to 14 days. The minimal treatment period was four days, but no longer than 21 days. Of the 592 patients treated with ZYVOX, 308 were started on oral therapy. Test-of-cure assessment was planned to be performed seven days after the end of treatment.

The incidence of drug-related adverse events appeared similar between treatment arms. Most adverse events in both groups were classified as mild to moderate. Drug-related adverse events in the ZYVOX-treated patients were noted more often in the digestive system and in lab tests documenting thrombocytopenia. Rash, anaphylaxis, drug-related allergic reaction and phlebitis were reported more often by patients in the vancomycin treatment group.

Source: Pfizer

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