Zosyn

ST. Louis -- Piperacillin/tazobactam (Zosyn) is a superb first-line agent for postoperative pelvic cellulitis, Dr. Sebastian Faro said at the 12th International Pelvic Reconstructive and Vaginal Surgery Conference.

Stay away from the cephalosporins for this purpose, he urged, explaining that most women undergoing hysterectomy or other pelvic surgery receive antibiotic prophylaxis with a cephalosporin. These drugs select for resistant bacteria, including Enterococcus faecalis and the very dangerous Enterobacter cloacae, said Dr. Faro, professor of ob.gyn. and an infectious disease specialist at the University of Texas, Houston.

An intravenous broad-spectrum penicillin and beta-lactamase inhibitor combination is an excellent first choice for pelvic cellulitis. The [beta]-lactamase inhibitor broadens the Penicillin's spectrum of activity against gram-negative organisms. Why intravenous therapy? Because postoperative pelvic cellulitis is a potentially serious infection that can result in pelvic abscess.

He rates piperacillin / tazobactam as his top choice ahead of ampicillin/sulbactam and ticarcillin! clavulanic acid because of piperacillin's superior activity against gram-negative bacteria.

Dr. Faro, who said he has no financial interest in Zosyn, noted that he doses the drug at 3.375 g IV every 6 hours.

If the patient isn't improving within 36-48 hours on Zosyn, however, it's time to add gentamicin. She is probably infected by a gram-negative organism or enterococcus.

"But if I give Zosyn, and 12 hours later she's deteriorating, I don't wait for 48 hours. I add the gentamicin right then," Dr. Faro said at the conference, sponsored by the Society of Pelvic Reconstructive Surgeons.

The combination of Zosyn and gentamicin offers coverage against anaerobes, gram-positive bacteria, and facultative gram-negative organisms. Piperacillin and gentamicin act synergistically against enterococci.

"When you combine Zosyn with gentamicin you really get very good coverage against most of the bacteria you have to deal with in ob.gyn.," he observed.

Dr. Faro prefers once-daily gentamicin dosing. The aminoglycoside's bactericidal effect increases as the drug concentration increases. And even though serum levels are undetectable for several hours before the next single daily dose, that's OK because gentamicin exhibits a postantibiotic bacteria-killing effect. There is reason to believe single daily dosing of gentamicin is less toxic because little or no tissue accumulation occurs during the last few hours before the next dose.

Single daily dosing of gentamicin is not appropriate in women with a creatinine clearance of less than 40 mL/min, hepatic disease, or postoperative fluid overload. Although there are no data assessing the drug's safety in pregnancy, Dr. Faro tries not to give it during the first trimester.

In prescribing gentamicin, it's imperative to obtain. serum drug levels. Failure to do so is hard to defend in a medicolegal situation.

"Get a trough level just before giving the gentamicin once-daily dose. If it's less than 1 [micro]g/mL, I'm happy If it's above that, I have to readjust my dose," the ob.gyn. said.

While he doesn't perform formal otologic testing in his gentamicin-treated patients, he does make a point of standing at the same spot in the hospital room and speaking at the same volume each time he visits them. It's a practical and informal means of checking on hearing.

When a patient isn't responding to gentamicin and a gram-negative facultative organism is thought to be the culprit, don't switch to tobramycin. The infection will be resistant to that drug, too. Instead, discontinue the gentamicin and initiate therapy with amikacin.

COPYRIGHT 2002 International Medical News Group
COPYRIGHT 2002 Gale Group