Question 1: Is Oseltamivir and/or Zanamivir safe in pregnancy?
The most recent CDC recommendations for the use of antiviral medications indicate that pregnant women and women up to two weeks postpartum with suspected or confirmed influenza should receive prompt empiric antiviral therapy.1
Although both oseltamivir and zanamivir may be considered for use during pregnancy 2,3, there is more safety data on oseltamivir than zanamivir in pregnant women.3,4
Oseltamivir
A recently published review article reports that oseltamivir and zanamivir are relatively safe drugs for use in pregnant and breastfeeding women.4 The review reports on data from two Japanese teratogen information services that found no increased risk for birth defects among 90 pregnant women exposed to oseltamivir (75 mg twice daily for up to five days) during the first trimester. In these cases, there was one (1.1%) incidence of malformation which is within the normal incidence rate of the general population (1-3%). The miscarriage rate was 3.3%, which is lower than that of general population, and four (4.4%) babies were premature.
Conclusion
Oseltamivir is the treatment of choice (75 mg twice daily for up to five days); zanamivir 10 mg (two 5-mg inhalations) twice daily for five days may be preferred in pregnant women when nausea and vomiting are present.
See websites below for additional information:
http://www.motherisk.org/women/commonDetail.jsp?content_id=914
http://www.phac-aspc.gc.ca/alert-alerte/h1n1/guidance-orientation-07-09-eng.php
1. Centers for Disease Control and Prevention: Updated Interim Recommendations for the Use of Antiviral Medications in the Treatment and Prevention of Influenza for the 2009-2010 Season. October 16, 2009 4:00 PM ET. Available at http://www.cdc.gov/H1N1flu/recommendations.htm. Accessed October 28, 2009.
2. European Medicines Agency (29 May, 2009) Follow-Up Recommendations from CHMP on Novel Influenza (H1N1) outbreak. EMEA/H/A-5.3/1172 Article 5(3) of Regulation (EC) No 726/2004.
3. Centre for Disease Control and Prevention (May 12, 2009) Novel influenza A (H1N1) virus infections in three pregnant women – United States, April – May 2009. MMWR Dispatch 58; 1-3.
4. Tanaka T, Nakajima K, Murashima A, Garcia-Bournissen F, Koren G, Ito S. Safety of neuraminidase inhibitors against novel influenza A (H1N1) in pregnant and breastfeeding women. CMAJ 2009;181(1-2):55-8.
Page last updated November 25, 2009
