The Role of the Newer Antimicrobial Agents in Obstetrics and Gynecology

The new antibiotics include interesting compounds--extended-spectrum cephalosporins and penicillins, combinations of older antibiotics plus beta-lactamase inhibitors, and new classes such as the monobactams and fluoroquinolones. In addition to extended spectrums, some of these compounds offer more favorable kinetics, less toxicity, or decreased cost. Several general conclusions might help place this array of new antibiotics in a useful clinical perspective. The newer antibiotics discussed here are no more effective than what is currently used. However, several have very good in-vitro activity against pelvic pathogens and are reasonable single-agent therapy in mild to moderate postpartum and postoperative infections. These antibiotics include cefoxitin, cefotetan, and piperacillin. Although moxalactam has good activity, its use is limited by concerns regarding bleeding disorders. Cefotaxime and cefoperazone have somewhat less favorable spectra, especially against anaerobes, yet in limited clinical trials are as effective as those cited above. Penicillin/beta-lactamase inhibitor combinations are currently being evaluated and appear to be reasonable choices. Although imipenem has an excellent in-vitro spectrum, it should probably be reserved for resistant cases. Aztreonam offers an alternative to gentamicin. However, in view of its greater cost, its use should be limited to patients in whom renal toxicity is a concern. For serious infections, combination therapy with clindamycin and gentamicin is our preference. For pelvic inflammatory disease, none of the agents is recommended as sole therapy due to the lack of coverage for chlamydia and frequent suboptimal coverage for anaerobes. Many of these agents have been effective for prophylaxis, but none has been shown to be superior to the older, less expensive agents such as cefazolin. Although many are effective in single doses, it is also likely that cefazolin is equally effective as a single dose. In addition, while most of the newer antibiotics are resistant to beta-lactamases themselves, they may induce their formation. This may ultimately result in limitations to the use of the relatively inexpensive prophylactic antibiotics.