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Notice to Readers: Updated Recommendations for Antimicrobial Prophylaxis Among Asymptomatic Pregnant Women After Exposure to Bacillus anthracis

The antimicrobial of choice for initial prophylactic therapy among asymptomatic pregnant women exposed to Bacillus anthracis is ciprofloxacin, 500 mg twice a day for 60 days. In instances in which the specific B. anthracis strain has been shown to be penicillin-sensitive, prophylactic therapy with amoxicillin, 500 mg three times a day for 60 days, may be considered. Isolates of B. anthracis implicated in the current bioterrorist attacks are susceptible to penicillin in laboratory tests, but may contain penicillinase activity (2). Pencillins are not recommended for treatment of anthrax, where such penicillinase activity may decrease their effectiveness. However, penicillins are likely to be effective for preventing anthrax, a setting where relatively few organisms are present. Doxycycline should be used with caution in asymptomatic pregnant women and only when contraindications are indicated to the use of other appropriate antimicrobial drugs.

Pregnant women are likely to be among the increasing number of persons receiving antimicrobial prophylaxis for exposure to B. anthracis. Clinicians, public health officials, and women who are candidates for treatment should weigh the possible risks and benefits to the mother and fetus when choosing an antimicrobial for postexposure anthrax prophylaxis. Women who become pregnant while taking antimicrobial prophylaxis should continue the medication and consult a health-care provider or public health official to discuss these issues.

No formal clinical studies of ciprofloxacin have been performed during pregnancy. Based on limited human information, ciprofloxacin use during pregnancy is unlikely to be associated with a high risk for structural malformations in fetal development. Data on ciprofloxacin use during pregnancy from the Teratogen Information System indicate that therapeutic doses during pregnancy are unlikely to pose a substantial teratogenic risk, but data are insufficient to determine that there is no risk (1). Doxycycline is a tetracycline antimicrobial. Potential dangers of tetracyclines to fetal development include risk for dental staining of the primary teeth and concern about possible depressed bone growth and defective dental enamel. Rarely, hepatic necrosis has been reported in pregnant women using tetracyclines. Penicillins generally are considered safe for use during pregnancy and are not associated with an increased risk for fetal malformation. Pregnant women should be advised that congenital malformations occur in approximately 2%--3% of births, even in the absence of known teratogenic exposure.

Additional information about the treatment of anthrax infection is available at <>.


  1. Friedman JM, Polifka JE. Teratogenic effects of drugs: a resource for clinicians (TERIS). Baltimore, Maryland: Johns Hopkins University Press, 2000:149--95.
  2. CDC. Update: investigation of bioterrorism-related anthrax and interim guidelines for exposure management and antimicrobial therapy, October 2001. MMWR 2001;50:909--19.

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