Microbial infection has always been a grave threat to obstetric and gynecologic patients. Developments in antimicrobial therapy, however, have led to decreases in puerperal and postoperative morbidity and perinatal mortality. Indeed antibiotic development is one of the most important advances in medicine in the 20th century. Empiric antibiotics for bacterial infections improve clinical symptoms and outcome. As a consequence, clinicians prescribe antibiotics very frequently and sometimes even when it is not necessary. This approach has led to huge overuse of antibiotics, which in turn has led to the appearance of multidrug-resistant bacteria. Clinicians need to adopt an approach where effective antibiotic treatment is given to those who have bacterial infections, while at the same time antibiotic use is limited when not indicated.
SELECTION OF ANTIMICROBIAL DRUGS
Several considerations are pertinent to most infections encountered in obstetric and gynecologic practice. First, the majority of patients are generally healthy and free of debilitating illness, with the exception of some elderly and oncology patients. Second, the lower genital tract (vagina and cervix) contains a complex flora (eg, anaerobes, gram-positive and gram-negative aerobes, and Candida), whereas the upper genital tract (uterus, fallopian tubes, and ovaries) is sterile. Infections in the upper genital tract usually result from spread of the lower genital tract flora when the upper tract is anatomically disrupted (eg, by sexually transmitted disease, by surgery, or during delivery). For this reason, most infections, such as postpartum or postoperative infection and pelvic inflammatory disease, are polymicrobial. Third, cultures must be obtained when infection is suspected (eg, pelvic abscess, chorioamnionitis), and empiric antibiotic therapy targeted at the potential organisms is usually indicated before culture results are available. However, in some gynecologic infections, because of laboratory limitations, culture results may not be available in a timely fashion, or tests may not even be performed at all. In some cases, surgical intervention (“source control”) rather than antibiotic treatment (“antibiotic control”) is the main component of treatment. Fourth, when selecting antibiotic agents in a pregnant woman, the potential risk for the fetus should be taken into account.
To serve as a guide to antibiotic selection, 5 tables are provided. Tables 46–1 and 46–2 provide the classification and dosages of selected β-lactam antibiotics and antibiotics from other classes. Table 46–3 presents the main or serious adverse events of antibiotics commonly used in obstetric-gynecologic practice and risk categories of antimicrobials in pregnancy. Table 46–4 shows recommended drugs and alternatives against selected bacteria encountered in obstetric-gynecologic practice. Finally, Table 46–5 shows suggested regimens for main clinical diagnoses.
Table 46–1.Antibiotic dosage of selected β-lactam agents. |Favorite Table|Download (.pdf) Table 46–1. Antibiotic dosage of selected β-lactam agents.
|Class, Agent ||Usual Adult Dosage in Normal Renal Function |
|Natural penicillins || |
|Benzathine penicillin G ||600,000–1.2 million units IM |
|Penicillin G ||2–4 million units IV q4h |
|Penicillin V ||0.25–0.5 g PO bid-qid |