Synercid I.V.

Synercid is indicated in adults for the treatment of the following infections when caused by susceptible strains of the designated microorganisms: One of Synercid's approved indications is for the treatment of patients with serious or life-threatening infections associated with vancomycin-resistant Enterococcus faecium (VREF) bacteremia. Synercid has been approved for marketing in the United States for this indication under FDA's accelerated approval regulations that allow marketing of products for use in life-threatening conditions when other therapies are not available. Approval of drugs for marketing under these regulations is based upon a demonstrated effect on a surrogate endpoint that is likely to predict clinical benefit. Approval of this indication is based upon Synercid’s ability to clear VREF from the bloodstream, with clearance of bacteremia considered to be a surrogate endpoint. There are no results from well-controlled clinical studies that confirm the validity of this surrogate marker. However, a study to verify the clinical benefit of therapy with Synercid on traditional clinical endpoints (such as cure of the underlying infection) is presently underway. Another disease would be complicated skin and skin structure infections caused by Staphylococcus aureus (methicillin susceptible) or Streptococcus pyogenes.

Results are available from four non-comparative studies of Synercid (7.5 mg/kg q8h) for the treatment of vancomycin-resistant Enterococcus faecium (VREF) (N=1222). Three of these studies were prospective, the fourth consisted of a collection of individual emergency-use requests. Of the 1222 patients, 27% did not have a specific site of infection identified, but presented with pure growth of VREF in two or more blood cultures. Ninety percent (90%) of these patients had clearance of their VREF bacteremia within the first 48 to 72 hours of therapy. Because of the emergency use nature of the VREF trials and the variability in data collection in these severely ill patients, the percentage of patients found to be evaluable was 24.4%. The overall efficacy rate (defined as clinical success and eradication of the initial pathogen) in the evaluable patients (n=298) was 52.3%. The most common sites of infection included intra-abdominal, skin and skin structure, and the urinary tract. In these subgroups, the efficacy rates for the evaluable patients having the most complete documentation were 46.3% (n=67), 66.7% (n=15), and 73.9% (n=23), respectively. Two randomized, open-label, controlled clinical trials of Synercid (7.5 mg/kg q12h intravenously [iv]) in the treatment of complicated skin and skin structure infections were performed. The comparator drug was oxacillin (2g q6h iv) in the first study (JRV 304) and cefazolin (1g q8h iv) in the second study (JRV 305); however, in both studies vancomycin (1g q12h iv) could be substituted for the specified comparator if the causative pathogen was suspected or confirmed methicillin-resistant staphylococcus or if the patient was allergic to penicillins, cephalosporins or carbapenems. Study JRV 304 enrolled 450 patients (n = 229 Synercid; n= 221 Comparator) and Study JRV 305 enrolled 443 patients (n = 221 Synercid; n = 222 Comparator). In the first study, 105 patients (45.9%) and 106 patients (48.0%) in the Synercid and Comparator arms, respectively, were found to be clinically evaluable. For the second study, these values were 113 (51.1%) and 120 (54.1%) patients in the Synercid and Comparator arms, respectively. Patients were found not to be clinically evaluable for reasons such as: wrong diagnosis, lower extremity infection in patients with diabetes or peripheral vascular disease since these infections were assumed to include aerobic gram-negative and anaerobic organisms, no specimen for culture obtained, insufficient therapy, no test of cure assessment, etc. For the patients found to be clinically evaluable, in Study JRV 304 the success rate was 49.5% in the Synercid arm and 51.9% in the Comparator arm. In Study JRV 305, the success rates were 66.4% and 64.2% in the Synercid and Comparator arms, respectively.

Serious adverse reactions in clinical trials, including non-comparative studies, considered possibly or probably related to Synercid administration with an incidence <0.1% include: acidosis, anaphylactoid reaction, apnea, arrhythmia, bone pain, cerebral hemorrhage, cerebrovascular accident, coagulation disorder, convulsion, dysautonomia, encephalopathy, grand mal convulsion, hemolysis, hemolytic anemia, heart arrest, hepatitis, hypoglycemia, hyponatremia, hypoplastic anemia, hypoventilation, hypovolemia, hypoxia, jaundice, mesenteric arterial occlusion, neck rigidity, neuropathy, pancytopenia, paraplegia, pericardial effusion, pericarditis, respiratory distress syndrome, shock, skin ulcer, supraventricular tachycardia, syncope, tremor, ventricular extrasystoles and ventricular fibrillation. Cases of hypotension and gastrointestinal hemorrhage were reported in less than 0.2% of patients.

The streptogramin components of Synercid, quinupristin and dalfopristin, are present in a ratio of 30 parts quinupristin to 70 parts dalfopristin. These two components act synergistically so that Synercid’s microbiologic in vitro activity is greater than that of the components individually. Quinupristin’s and dalfopristin’s metabolites also contribute to the antimicrobial activity of Synercid. In vitro synergism of the major metabolites with the complementary parent compound has been demonstrated. Synercid is bacteriostatic against Enterococcus faecium and bactericidal against strains of methicillin-susceptible and methicillin-resistant staphylococci. The site of action of quinupristin and dalfopristin is the bacterial ribosome. Dalfopristin has been shown to inhibit the early phase of protein synthesis while quinupristin inhibits the late phase of protein synthesis. In vitro combination testing of Synercid with aztreonam, cefotaxime, ciprofloxacin, and gentamicin against Enterobacteriaceae and Pseudomonas aeruginosa did not show antagonism. In vitro combination testing of Synercid with prototype drugs of the following classes: aminoglycosides (gentamicin), $-lactams (cefepime, ampicillin, and amoxicillin), glycopeptides (vancomycin), quinolones (ciprofloxacin), tetracyclines (doxycycline) and also chloramphenicol against enterococci and staphylococci did not show antagonism. The mode of action differs from that of other classes of antibacterial agents such as $-lactams, aminoglycosides, glycopeptides, quinolones, macrolides, lincosamides and tetracyclines. There is no cross resistance between Synercid and these agents when tested by the minimum inhibitory concentration (MIC) method. In non-comparative studies, emerging resistance to Synercid during treatment of VREF infections occurred. Resistance to Synercid is associated with resistance to both components (i.e., quinupristin and dalfopristin).

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