From the Guidelines
Alternative antibiotics for anaerobic coverage besides Zosyn include metronidazole, clindamycin, carbapenems (meropenem, imipenem, ertapenem), moxifloxacin, and tigecycline. According to the guidelines for the selection of anti-infective agents for complicated intra-abdominal infections 1, and the diagnosis and management of complicated intra-abdominal infection in adults and children 1, these antibiotics are recommended for anaerobic coverage.
Key Points to Consider
- Metronidazole (500 mg IV/PO every 8 hours) is often the first choice due to its excellent anaerobic spectrum, particularly against Bacteroides fragilis, and minimal resistance 1.
- Clindamycin (600-900 mg IV every 8 hours) provides good coverage but has increasing resistance rates 1.
- Carbapenems offer broad-spectrum coverage including anaerobes, with meropenem (1 g IV every 8 hours), imipenem (500 mg IV every 6 hours), or ertapenem (1 g IV daily) being effective options for serious infections 1.
- Moxifloxacin (400 mg IV/PO daily) provides moderate anaerobic coverage along with gram-positive and gram-negative activity 1.
- Tigecycline (100 mg IV loading dose, then 50 mg IV every 12 hours) covers anaerobes but has limitations including FDA warnings about mortality risk 1.
Patient Factors to Consider
- Infection site and severity
- Patient allergies and renal function
- Local resistance patterns
Additional Considerations
- Combination therapy may be necessary for polymicrobial infections, such as metronidazole plus a cephalosporin for broader coverage 1.
From the FDA Drug Label
Clindamycin is indicated in the treatment of serious infections caused by susceptible anaerobic bacteria. The usual adult oral dosage is 7.5 mg/kg every six hours (approx. 500 mg for a 70 kg adult) for metronidazole.
Alternative antibiotics for anaerobic coverage (excluding Zosyn) are:
- Metronidazole 2: used to treat serious anaerobic infections
- Clindamycin 3: indicated in the treatment of serious infections caused by susceptible anaerobic bacteria
From the Research
Alternative Antibiotics for Anaerobic Coverage
Excluding Zosyn (piperacillin/tazobactam), the following antibiotics can be used for anaerobic coverage:
- Metronidazole, which is highly effective against all species of anaerobes except certain non-spore-forming gram-positive bacilli and cocci 4
- Clindamycin, which has been used successfully in some anaerobic infections, although its susceptibility has decreased over time 5
- Imipenem, which is one of the most active agents against anaerobic bacteria 5, 6
- Meropenem, which has been shown to be highly active against anaerobic bacteria and is a promising antimicrobial agent for anaerobic infections 6, 7
- Chloramphenicol, which is effective against anaerobic organisms 5, 7
- Tigecycline, which is effective against anaerobic organisms 7
- Combinations of a penicillin and a beta-lactamase inhibitor, such as ampicillin or ticarcillin plus clavulanate, amoxicillin plus sulbactam 7
- RP 59500, a new streptogramin, which has been shown to be highly active against anaerobic bacteria 8
- Cefoxitin, which has been used successfully in some anaerobic infections 5
- Fluoroquinolones, which exhibit good activity against Gram-positive cocci and anaerobes 5