With the H1N1 flu outbreak now elevated to pandemic level, a new article in CMAJ (Canadian Medical Association Journal) reports that oseltamivir (Tamiflu) and zanamivir (Relenza) are relatively safe drugs for use in pregnant and breast-feeding women.
Pregnant women, especially those in the third trimester, are at high risk of serious complications from the H1N1 A influenza virus.
The study was conducted by researchers from the Motherisk Program at The Hospital for Sick Children (SickKids) in Toronto and the Japan Drug Information Institute in Pregnancy in Tokyo, Japan.
For treatment or prevention during the current pandemic, "oseltamivir appears to be the drug of choice because there are more data on its safety in pregnancy," writes Dr. Shinya Ito, Head of the Division of Clinical Pharmacology and Toxicology at SickKids. Zanamivir can be used, although there is less data available about its safety in pregnant women. Neither drug appears to affect the growth and development of the fetus, although ongoing data collection is important. The groups at high risk of flu-related complications from the novel H1N1 influenza are the same as those for seasonal flu - pregnant women, children under 5 years, the elderly and others such as those with chronic lung conditions.
Only small amounts of oseltamivir and zanamivir are excreted into human milk. If an infant is breastfed by the mother on these drugs and needs treatment, the recommended dose of oseltamivir or zanamivir should be given to the infant.