Acyclovir and Valacyclovir Pregnancy Registries

The Acyclovir Pregnancy Registry, established in 1984, and Valacyclovir Pregnancy Registry, established in 1995, were completed in 1999. A final study is available to interested healthcare providers by calling the GlaxoSmithKline Customer Response Center at 1-888-825-5249 (toll-free).

The Acyclovir/Valacyclovir Pregnancy Registries were designed to assess the outcomes of pregnancies exposed to acyclovir and valacyclovir, and provide an early signal of potential risks of these drugs to the developing fetus. Data on outcomes from 1129 prospectively followed acyclovir-exposed pregnancies (712 involving first trimester exposure) and 56 valacyclovir-exposed pregnancies (14 involving first trimester exposure) were reported to these voluntary registries from June 1984 (acyclovir) and January 1995 (valacyclovir) through December 1997.

The Acyclovir/Valacyclovir Pregnancy Registry Advisory Committee recommended that these prenatal drug exposure registries be closed. Registration of pregnancies exposed to these drugs was discontinued July 31, 1998. Pregnancies registered prior to this date were followed through ascertainment of their outcome.

The Advisory Committee concluded: "The [Acyclovir Pregnancy] Registry findings to date do not show an increase in the number of birth defects identified among the prospective reports [of exposures to acyclovir] when compared with those expected in the general population. In addition, there is no pattern of defects among prospective or retrospective acyclovir reports. These findings should provide some assurance in counseling women following prenatal exposure [to acyclovir]" (1,2). The Committee recommended that healthcare providers follow the Centers for Disease Control and Prevention 1998 Guidelines for Treatment of Sexually Transmitted Diseases (3). Reports to the Valacyclovir Pregnancy Registry of pregnancy exposure to valacyclovir were low in number, resulting in insufficient data for analysis of risk.

The Committee believed that it was unlikely that additional information collected by these registries would have added substantially to our knowledge about the safety of acyclovir and valacyclovir. However, GlaxoSmithKline remains committed to studying the safety of ZOVIRAX® (acyclovir) and VALTREX® (valacyclovir hydrochloride) in pregnancy. As for all of the sponsor’s marketed products, these drugs are now monitored through the GlaxoSmithKline Worldwide Product Surveillance and Pharmacovigilance Department (by calling 1-888-825-5249, toll-free). Safety review and regulatory reporting by this department provides a mechanism for detecting potential safety issues and reporting them to healthcare professionals.


  1. Acyclovir Pregnancy Registry and Valacyclovir Pregnancy Registry Interim Report, December 1997. Glaxo Wellcome, RTP, NC 27709
  2. Centers for Disease Control and Prevention: Metropolitan Atlanta Congenital Defects Program, revised January 1998.
  3. CDC 1998 Guidelines for Treatment of Sexually Transmitted Diseases. MMWR 1998; 47:No. RR-1.

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