Is Oseltamivir (Tamiflu) safe in a pregnant patient?

From the Guidelines

Tamiflu (oseltamivir) can be safely used in pregnant patients with influenza, as the benefits of treatment generally outweigh the potential risks of the medication. The recommended dosage is 75 mg twice daily for 5 days, ideally started within 48 hours of symptom onset for maximum effectiveness 1. Pregnancy is considered a high-risk condition for influenza complications, making prompt treatment important. Oseltamivir works by inhibiting viral neuraminidase, preventing the release of new virus particles from infected cells. This helps reduce the duration and severity of symptoms while potentially preventing serious complications like pneumonia.

Some key points to consider when using oseltamivir in pregnant patients include:

• The medication should be administered orally without regard to meals, although administration with meals may improve gastrointestinal tolerability 1.
• Side effects may include nausea and vomiting, which can be minimized by taking the medication with food.
• Pregnant patients with influenza should also maintain adequate hydration, consider acetaminophen for fever control, and seek immediate medical attention if experiencing difficulty breathing, chest pain, persistent fever, or decreased fetal movement.
• The CDC recommends routine chemoprophylaxis with oseltamivir or zanamivir for 7 days after last known exposure; minimum of 14 days and continuing for 7 days after last known exposure if part of institutional outbreak 1.

It's essential to note that while oseltamivir is considered safe for use in pregnant patients, the medication is classified as "Pregnancy Category C," indicating that no clinical studies have been conducted to assess its safety in pregnant women 1. However, multiple studies have demonstrated that the benefits of treating influenza during pregnancy generally outweigh the potential risks of the medication 1.

From the FDA Drug Label

There are no adequate and well-controlled studies with oseltamivir phosphate for oral suspension in pregnant women to inform a drug-associated risk of adverse developmental outcomes. Available published epidemiological data suggest that oseltamivir phosphate for oral suspension, taken in any trimester, is not associated with an increased risk of birth defects However, these studies individually are limited by small sample sizes, use of different comparison groups, and some lacked information on dose, which preclude a definitive assessment of the risk

Published prospective and retrospective observational studies of more than 5,000 women exposed to oseltamivir phosphate during pregnancy, including more than 1,000 women exposed in the first trimester, suggest that the observed rate of congenital malformations was not increased above the rate in the general comparison population, regardless of when therapy was administered during the gestational period.

Oseltamivir (Tamiflu) use in pregnant patients:

• There are no adequate and well-controlled studies to inform a drug-associated risk of adverse developmental outcomes.
• Available epidemiological data suggest no increased risk of birth defects when taken in any trimester.
• However, the studies have limitations, including small sample sizes and lack of dose information.
• Pregnant women are at higher risk of severe complications from influenza, which may lead to adverse pregnancy and/or fetal outcomes.
• The decision to use oseltamivir in pregnant patients should be made on a case-by-case basis, considering the potential benefits and risks 2.

From the Research

Safety of Oseltamivir in Pregnant Patients

• Oseltamivir (Tamiflu) is currently the first-line recommended and most commonly used pharmaceutical agent for influenza prophylaxis and treatment in pregnant women 3, 4.
• The physiologic adaptations of pregnancy may alter the pharmacokinetics and pharmacodynamics of oseltamivir, but evidence suggests that it is safe and effective for use in pregnant women 3, 4.
• Antiviral treatment with oseltamivir is necessary for all pregnant women with suspected or confirmed influenza, regardless of vaccination status, and should be prescribed promptly based on clinical evaluation 5, 6.
• Treatment with oseltamivir within 48 hours of the onset of symptoms is ideal, but treatment should not be withheld if the ideal window is missed 5, 6.
• There is no evidence of adverse fetal outcomes as a result of most in utero exposures to oseltamivir, but large, population-based studies are needed to assess the association between in utero oseltamivir exposure and fetal outcome 7.

Recommendations for Use

• Pregnant women with suspected or confirmed influenza infection should receive antiviral treatment with oseltamivir or zanamivir based on the current resistance patterns 5, 6.
• Postexposure antiviral chemoprophylaxis can be considered for pregnant women and women who are up to 2 weeks postpartum who have had close contact with infectious individuals 5, 6.
• Vaccination is the most effective strategy for preventing influenza infection during pregnancy, and can protect both maternal and fetal immunities 7.