Oseltamivir Pregnancy and Breastfeeding Warnings

Oseltamivir is also known as: Tamiflu

Oseltamivir Pregnancy Warnings

Oseltamivir has been assigned to pregnancy category C by the FDA. Animal data, in which doses equivalent to 2 to 100 times the maximum recommended human dose (MRHD) were given, have revealed that the drug crosses the placenta. These data have also revealed maternal toxicity (slight at lower doses, marked at higher doses) and a dose-dependent increase in the incidence of a variety of minor skeletal abnormalities and variants in the exposed offspring. There are no data (controlled or anecdotal) from human pregnancy. Oseltamivir should only be given during pregnancy when benefit outweighs risk.

Oseltamivir Breastfeeding Warnings

Oseltamivir and its active metabolite are excreted into human milk. The effects in the nursing infant are unknown. The manufacturer recommends that oseltamivir should be used only if the potential benefit for the lactating mother justifies the potential risk to the breastfed infant.

A woman who was breastfeeding her 9-month-old infant was treated with oseltamivir 75 mg twice a day for 5 days after accidentally sticking herself with a needle contaminated with 2009 H1N1 influenza virus. Breastfeeding was stopped during this time due to possible side effects in the infant. Eleven milk samples were collected twice daily over the 5-day period by completely emptying both breasts. The sample timing varied, with 8 of the samples collected 30 minutes before or after a dose. The steady-state concentration of the metabolite was reached after 3 days and averaged 37 to 39 ng/mL. The maximum relative infant dose (oseltamivir plus metabolite) was estimated to be 0.012 mg/kg/day, or about 0.5% of the mother's weight-adjusted dose (assuming 60 kg body weight). Based on this study, the concentration of the drug in breast milk appears to be clinically insignificant. Also, the potential dose for a nursing infant is much less than the pediatric dose. Additionally, the Centers for Disease Control and Prevention recommend women infected with 2009 H1N1 influenza virus breastfeed, regardless of whether they are being treated, due to the advantages of breast milk for the infant's immune system.

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