MedWire News: It is acceptable for pregnant women requiring treatment for the novel influenza A H1N1 virus to be treated treated with oseltamivir, research shows.

Zanamivir, which is a similar neuraminidase inhibitor, can also be used in pregnant women, although there is less supporting safety data, according to a review by Toshihiro Tanaka (Sick Children's Hospital, Toronto, Canada) and colleagues in the Canadian Medical Association Journal.

Pregnant women, especially those in the late stages of pregnancy, are at high risk for complications from influenza, including H1N1 strain. A recent government report stated that 15 confirmed and five probable H1N1 infections in the US were in pregnant women.

"Although the novel H1N1 influenza virus may not be as virulent as anticipated, the increased risk of complications during pregnancy should be taken into account when caring for affected patients," comment Tanaka and colleagues.

The group summarized available safety data on the use of neuraminidase inhibitors for the treatment of the H1N1 influenza in pregnant and breastfeeding women.

Their review suggests that oseltamivir is not a major teratogen for humans.

Although zanamivir may be used, there are fewer data available about its safety in pregnant women, say the researchers.

The group also reviewed use of these medications in lactating women.

"Both oseltamivir and zanamivir are considered to be compatible with breastfeeding," the group reports. "Continuation of breastfeeding by a woman taking these medications is unlikely to lead to substantial drug exposure by the infant."

A dose adjustment in breastfeeding mothers is not required, the team recommends. Infants requiring treatment can also be prescribed the drugs, although the dose should be adjusted based on their weight.

In adults, the therapeutic dose of oseltamivir, a prodrug hydrolyzed by the liver, is 75 mg twice daily for 5 days, starting within 48 hours of initial symptoms. The therapeutic dose of zanamivir is 10 mg inhaled twice daily for 5 days and is also started within 48 hours of initial symptoms. For prophylaxis, treatment with both agents is continued for 10 days.

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009

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