Magazine article Drug Topics

New Once-Daily Antibiotic Treats Mixed Infections

Magazine article Drug Topics

New Once-Daily Antibiotic Treats Mixed Infections

Article excerpt




The Food & Drug Administration's late-November approval of Merck's once-daily carbapenem antibiotic, Inva-nz (ertapenem), will offer a new option for the IV or IM treatment of community-acquired mixed infections.

Ertapenem, whose spectrum of activity covers a wide range of grampositive and gram-negative aerobic and anaerobic organisms, is indicated for the treatment of adults with complicated intra-abdominal infections, complicated skin and skin structure infections, community-acquired pneumonia (CAP), complicated urinary tract infections, and acute pelvic infections.

In 13 phase IIb/III clinical trials that evaluated the new antibiotic in more than 1,900 patients, ertapenem demonstrated cure rates similar to those of comparator drugs Zosyn (piperacillin/tazobactam, Wyeth-Ayerst) and Rocephin (ceftriaxone, Roche). Antibiotics were administered for three to 14 days; in some studies, patients could be switched to oral antimicrobials to complete therapy The combination of piperacillin and tazobactam was used as the comparator in the intraabdominal, skin, and pelvic infection studies, while ceftriaxone was used in the CAP and UTI studies.

Because ertapenem "has very good stability against most betalactamases," said Robin Isaacs, M.D., senior director of clinical research at Merck Research Laboratories, it covers many isolates that are resistant to other beta-lactams, including broad-spectrum penicillins and cephalosporins. However, she noted that, unlike other carbapenems, ertapenem is not active against Pseudomonas or Acinetobacter, which are common pathogens in hospitalacquired infections.

An advantage of ertapenem, said Ron E. Polk, Pharm.D., professor of pharmacy and medicine at Virginia Commonwealth University School of Pharmacy in Richmond, is that it can be used "once a day for infections that are often treated with more frequent dosing or with therapy that requires more than one drug." The piperacillin/tazobactam combo, for instance, is administered q6h, while once-daily ceftriaxone, which does not cover anaerobes, must be combined with a second antimicrobial for mixed infections where anaerobic involvement is suspected.

Isaacs stressed the "simplicity" associated with ertapenem's dosing: one drug, 1 gm, once a day. The 1-gm dose is the same for all indications, although recommended durations of therapy differ. Dosage adjustment is necessary only for patients with advanced or end-stage renal insufficiency. …

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