Anthrax prophylaxis, treatment during pregnancy

OB/GYN News, Nov 15, 2001 by Elizabeth Mechcatie

The decision about which drug to prescribe for anthrax prophylaxis or therapy should always be based on what's best for the mother, according to Gerald Briggs, clinical professor of pharmacy at the University of California, San Francisco.

Severe maternal toxicity can result from anthrax exposure. In this situation, fetal safety becomes a secondary issue, even though prolonged antibiotic courses, in the absence of a vaccine, raise some safety concerns for the fetus, said Mr. Briggs, the pharmacist clinical specialist at Women's Hospital, Long Beach (Calif.) Memorial Medical Center.

Mr. Briggs, coauthor of the textbook "Drugs in Pregnancy and Lactation" (Baltimore: Williams & Wilkins, 1997), made these recommendations on the safety of various agents for anthrax prophylaxis and treatment:

* Ciprofloxacin (Cipro). The benefits of ciprofloxacin "certainly outweigh the risk," Mr. Briggs said. While there has been some concern that ciprofloxacin exposure in utero maybe related to some birth defects, no causal relationship has been established.

There is a theoretical risk of cartilage damage in exposed fetuses and subsequent arthropathies, and there have been reports of cartilage damage in infants given the drug directly.

* Doxycycline. He considers the tetracyclines to be the last choice for pregnant women. Doxycycline is not a human teratogen but can cause discoloration of primary teeth when exposure occurs anytime from the middle of the second trimester to term. While inhibition of fetal bone growth can also occur, this has not been clinically significant, but prolonged exposure has not been studied. Still, although Mr. Briggs considers this class of drugs to be the last choice for use in pregnancy if a woman had no other choice, she should take them.

* Penicillin and amoxicillin. These agents are safe during pregnancy and are his first choice if the anthrax is sensitive to them. In that case, intravenous penicillin is indicated for chemotherapy and oral amoxicillin is indicated for chemoprophylaxis.

Mr. Briggs recommended that if a patient is allergic to penicillin, "consideration should be given to desensitizing the mother," particularly when long-term therapy is planned. He referred to a 12-hour desensitization protocol, which has been shown to be effective in pregnant women with documented anaphylaxis.

Gentamicin, erythromycin, and chloramphenicol are potential drug alternatives for treating anthrax, according to "Medical Management of Biological Casualties handbook," published by the U.S. Army Medical Research Institute of Infectious Diseases.

* Gentamicin. It is not teratogenic but with prolonged therapy has the potential for causing ototoxicity and renal toxicity in both the mother and the fetus. Mr. Briggs recommended checking serum levels and maternal renal function frequently in pregnant women on prolonged gentamicin therapy To minimize high levels of this agent in the mother and, thus, in the fetus, avoid single-dose therapy and administer the daily dose in divided doses.

"And I would definitely avoid concurrent administration of other ototoxic and renal toxic drugs," Mr. Briggs advised, adding that he would also monitor for hearing loss women on prolonged gentamicin therapy.

* Erythromycin. Basically, this antibiotic is safe to use in pregnancy and is a good drug to use, if tolerated.

* Chloramphenicol. It is not a human teratogen, but can in rare cases cause aplastic anemia. If given at a high enough dose to an infant, it can produce cardiovascular collapse (gray syndrome).