Zyvox Demonstrates Higher Success Rate Over Vancomycin for Patients Who Develop MRSA Surgical Site Infections

NEW YORK -- Surgical patients treated with Pfizers novel antibiotic ZYVOX® (linezolid; injection, tablets, and for oral suspension) had a significantly higher rate of microbiologic success (documented or presumed eradication) than those treated with intravenous (IV) vancomycin for surgical site infections (SSIs) caused by methicillin-resistant Staphylococcus aureus (MRSA), according to data published in the December issue of the American Journal of Surgery.  In addition, the mean duration of IV treatment was significantly shorter (six days) for patients who received ZYVOX than for those treated with vancomycin.  Post-operative surgical site infections remain a major source of illness and number approximately 500,000 per year. 

In the post-hoc analysis, patients in the MRSA subgroup treated with ZYVOX had microbiologic success rates of 87 percent compared to 48 percent for patients on vancomycin.  Clinical cure rates for ZYVOX-treated patients were comparable to those treated with vancomycin for all SSIs, including those caused by MRSA.  ZYVOX, available in interchangeable IV and oral formulations, is the only oral therapy approved by the U.S. Food and Drug Administration for MRSA infections.

Patients who develop SSIs are 60 percent more likely to spend time in an intensive care unit, five times more likely to be readmitted to the hospital and twice as likely to die.  Hard-to-treat resistant bacteria such as MRSA are further complicating these infections.  MRSA is extremely serious and can lead to prolonged hospitalization, increased morbidity, increased risk of mortality, and increased costs (driven by length of hospital stay).  Data show that MRSA caused 30 percent of SSIs in 2000 compared to 24 percent in 1997. 

As the prevalence of surgical site infections caused by MRSA increases, identifying MRSA early and having alternatives to vancomycin becomes extremely important since any patient undergoing surgery is at risk, 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 demonstrate that ZYVOX had significantly higher microbiologic success rates compared to vancomycin in patients with surgical site infections caused by MRSA, providing an important therapeutic alternative to vancomycin with the added convenience of both IV and oral formulations.

Study Results

MRSA-infected patients treated with ZYVOX had a microbiologic success rate of 87 percent (26/30) compared to 48 percent (14/29) in vancomycin-treated patients.  The clinical cure rates for the two study groups were comparable among all study populations.  In the microbiologically evaluable population, the microbiologic cure rate was 84 percent (41/49) for the ZYVOX group versus 58 percent (28/49) for the vancomycin group whether or not the patient was infected with MRSA.  In the ZYVOX arm, most patients (n=42) were treated exclusively with oral ZYVOX, while 24 received the IV formulation.  Although the total length of treatment among groups was comparable, the mean duration of IV treatment was significantly shorter for patients who received ZYVOX than for patients who received vancomycin (4.7 vs. 11.1 days, respectively). 

 The ability to treat MRSA with oral ZYVOX may reduce patients risk for additional infections and allow them to potentially recover in the comfort of their own home without the need for an IV line which is especially important in instances where the patient would not otherwise be hospitalized, said Weigelt.  Previous studies have demonstrated cost savings associated with oral ZVYOX due to shorter hospital stays.

This subset analysis of 135 patients with SSI was taken from a large, randomized, open-label, comparator-controlled, multicenter, multinational trial of 1,200 patients designed to compare the clinical efficacy, safety, and tolerability of ZYVOX vs. vancomycin for complicated skin and soft tissue infections.  The intent-to-treat (ITT) population consisted of 66 patients who received ZYVOX and 69 patients who received vancomycin.  Sixty-five patients in the ITT population had surgical site infections caused by MRSA.

Patients were randomized to receive ZYVOX 600 mg (IV or oral) every 12 hours or vancomycin (IV) 1 g every 12 hours for seven to 21 days.  The primary efficacy outcome was clinical response to treatment seven days after completing therapy.  Microbiologic outcome was defined as success (documented or presumed eradication of the pathogen), failure (persistence or progression of clinical signs and symptoms of infection after at least two days of study drug), and indeterminate (inability to classify to other categories). 

All patients who received more than one dose of study medication were included in the safety analysis.  Study investigators recorded adverse events and determined their severity.

The most common adverse events reported for both drugs were gastrointestinal and hematological in nature, including nausea, vomiting, constipation and anemia.  Diarrhea, thrombocytopenia and anorexia were reported more frequently in patients who took ZYVOX.  The drug was discontinued in eight percent of the ZYVOX patients and four percent of the vancomycin patients.  Serious adverse events occurred in 10 patients (15 percent) in the ZYVOX group and six patients (9 percent) in the vancomycin group.

ZYVOX is indicated in the treatment of the following infections caused by susceptible strains of the designated microorganisms:

           Nosocomial pneumonia caused by Staph aureus (methicillin-susceptible and -resistant strains) or Streptococcus pneumoniae (including multidrug-resistant strains [MDRSP]). MDRSP refers to isolates resistant to two or more of the following antibiotics: penicillin, second-generation cephalosporins, macrolides, tetracycline, and trimethoprim/sulfamethoxazole.  Combination therapy may be clinically indicated if the documented or presumptive pathogens include Gram-negative organisms

           cSSSIs, including diabetic foot infections, without concomitant osteomyelitis, caused by       S aureus (methicillin-susceptible and -resistant strains), Streptococcus pyogenes, or Streptococcus agalactiae.  ZYVOX has not been studied in the treatment of decubitus ulcers.  Combination therapy may be clinically indicated if the documented or presumptive pathogens include Gram-negative organisms

Myelosuppression (including anemia, leukopenia, pancytopenia, and thrombocytopenia) has been reported in patients receiving linezolid.  In cases where the outcome is known, when linezolid was discontinued, the affected hematologic parameters have risen toward pretreatment levels.  Complete blood counts should be monitored weekly in patients who receive linezolid, particularly in those who receive linezolid for longer than 2 weeks, and in other at-risk patients.

As with nearly all antibacterial agents, pseudomembranous colitis has been reported with ZYVOX. Therefore, it is important to consider this diagnosis in patients who present with diarrhea subsequent to the administration of ZYVOX.

ZYVOX formulations are contraindicated for use in patients who have known hypersensitivity to linezolid or any of the other product components.

To reduce the development of drug-resistant bacteria and maintain the effectiveness of ZYVOX and other antibacterial drugs, ZYVOX should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria.  When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy.  In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy.

Lactic acidosis has been reported with the use of ZYVOX.  In reported cases, patients experienced repeated episodes of nausea and vomiting.  Patients who develop recurrent nausea or vomiting, unexplained acidosis, or a low bicarbonate level while receiving ZYVOX should receive immediate medical evaluation.

The most commonly reported adverse events in adults across clinical trials were nausea, headache, and diarrhea.