Registry of acyclovir use during pregnancy

American Family Physician,  May, 1992  

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An international registry of acyclovir use in pregnancy was established in 1984 by Burroughs Wellcome and the Centers for Disease Control to monitor potential fetal risk from exposure to acyclovir during pregnancy. Acyclovir is widely used by sexually active women, particularly for the treatment and suppression of genital herpes, and inadvertent use during early pregnancy is highly possible. It is estimated that up to 50 percent of all users of acyclovir in this country are women of childbearing age. Although the drug has not been found to be teratogenic in standard tests in mice, rabbits and rats, very high doses have been associated with fetal abnormalities in rats. In addition, in vitro studies have linked very high dosages of acyclovir to chromosomal damage in human lymphocytes. Acyclovir is known to cross the placenta and to be concentrated in the fetal kidney. It is currently a category C drug--it should not be used in pregnancy unless the potential benefits outweigh the risk to the fetus.

The registry collects data on exposure during pregnancy and attempts to correlate exposure with pregnancy outcome. Patients are registered by their attending physician. Between June 1984 and June 1990, 312 cases were registered prospectively and 145 were registered retrospectively. Over 60 percent of the prospective cases were from the United States. Among the 239 prospectively reported cases of exposure during the first trimester, there were nine congenital abnormalities, 24 spontaneous abortions and 47 induced abortions. Only one of the 73 infants born following later exposure had a congenital abnormality. These results do not show an increased incidence of congenital abnormality in infants exposed to acyclovir. in utero, compared with the general population. In addition, the lack of any consistent pattern of abnormality indicates that acyclovir does not seem to cause a specific fetal abnormality or syndrome.

Although the findings to date are reassuring, the number of cases is still too small to make reliable and definitive conclusions about the use of acyclovir in pregnancy. Until more information is available, physicians should continue to follow category C guidelines. Physicians are encouraged to report cases of prenatal acyclovir exposure to the registry by calling 800-722-9292. (Obstetrics and Gynecology, January 1992, vol. 79, p. 7. )

COPYRIGHT 1992 American Academy of Family Physicians
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