Infectious Disease Consult

Appropriate antibiotic selection for 12 common infections in obstetric patients

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Antibiotic selection

In the first trimester of pregnancy, vulvovaginal candidiasis should be treated with a topical medication such as clotrimazole cream 1% (50 mg intravaginally daily for 7 days), miconazole cream 2% (100 mg intravaginally daily for 7 days), or terconazole cream 0.4% (50 g intravaginally daily for 7 days). Single-dose formulations or 3-day courses of treatment may not be quite as effective in pregnant patients, but they do offer a more convenient dosing schedule.2,5

Oral fluconazole should not be used in the first trimester of pregnancy because it has been associated with an increased risk for spontaneous abortion and with fetal cardiac septal defects. Beyond the first trimester, oral fluconazole offers an attractive option for treatment of vulvovaginal candidiasis. The appropriate dose is 150 mg initially, with a repeat dose in 3 days if symptoms persist.2,5

Ibrexafungerp (300 mg twice daily for 1 day) was recently approved by the US Food and Drug Administration (FDA) for oral treatment of vulvovaginal candidiasis. However, this drug is teratogenic and is contraindicated during pregnancy and lactation. It also is significantly more expensive than fluconazole.6

3. Cesarean delivery prophylaxis

All women having a cesarean delivery (CD) should receive antibiotic prophylaxis to reduce the risk of endometritis and wound infection.

Antibiotic selection

In my opinion, the preferred regimen is intravenous cefazolin 2 g plus azithromycin 500 mg administered preoperatively.7 Cefazolin can be administered in a rapid bolus; azithromycin should be administered over 1 hour.

In an exceptionally rigorous investigation called the C/SOAP trial (Cesarean Section Optimal Antibiotic Prophylaxis trial), Tita and colleagues showed that the combination of cefazolin plus azithromycin was superior to single-agent prophylaxis (usually with cefazolin) in preventing the composite of endometritis, wound infection, or other infection occurring within 6 weeks of surgery.8 The additive effect of azithromycin was particularly pronounced in patients having CD after labor and rupture of membranes. Harper and associates subsequently validated the cost-effectiveness of this combination regimen using a decision analytic model.9

If the patient has a serious allergy to β-lactam antibiotics, the best alternative regimen for prophylaxis is clindamycin plus gentamicin. The appropriate single intravenous dose of clindamycin is 900 mg; the single dose of gentamicin should be 5 mg/kg of ideal body weight (IBW).7

4. Chlamydia

Chlamydia trachomatis is an obligate intracellular bacterium. In pregnant women, it typically causes urethritis, endocervicitis, and inflammatory proctitis. Along with gonorrhea, it is the cause of an unusual infection/inflammation of the liver capsule, termed Fitz-Hugh-Curtis syndrome (perihepatitis). The diagnosis of chlamydia infection is best confirmed with a nucleic acid amplification test (NAAT). The NAAT simultaneously tests for chlamydia and gonorrhea in urine or in secretions obtained from the urethra, endocervix, and rectum.2

Antibiotic selection

The drug of choice for treating chlamydia in pregnancy is azithromycin 1,000 mg orally in a single dose. Erythromycin can be used as an alternative to azithromycin, but it usually is not well tolerated because of gastrointestinal adverse effects. In my practice, the preferred alternative for a patient who cannot tolerate azithromycin is amoxicillin 500 mg orally 3 times daily for 7 days.2,10

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