Is Oseltamivir (Tamiflu) safe during pregnancy?

From the Guidelines

Oseltamivir (Tamiflu) can be safely used during pregnancy when the benefits outweigh the risks, as it is recommended for pregnant women with confirmed or suspected influenza, especially if they are at high risk for complications. The use of oseltamivir in pregnant women is supported by the fact that pregnancy should not be considered a contraindication to its use, as stated in the guidelines from the Advisory Committee on Immunization Practices 1.

The standard adult dosage for treatment is 75 mg twice daily for 5 days, and for prevention, it's 75 mg once daily for at least 10 days after exposure, with the recommendation to start treatment as soon as possible, ideally within 48 hours of symptom onset for maximum effectiveness. It is crucial to note that oseltamivir is preferred for treatment of pregnant women due to its effectiveness in reducing the severity and duration of illness, which is particularly important for pregnant women who are at higher risk for severe complications from influenza 1.

Key points to consider include:

• Oseltamivir is classified as a "Pregnancy Category C" medication, indicating that data from clinical studies are not adequate to assess its safety for pregnant women, but no causal relation between its use and adverse events has been established 1.
• Reducing fever, whether directly by using antipyretics or indirectly by reducing the duration and severity of symptoms with antiviral medications like oseltamivir, might reduce the risk of adverse fetal outcomes 1.
• A retrospective cohort study found no evidence of an association between oseltamivir use during pregnancy and adverse events such as preterm birth, premature rupture of membranes, increased duration of hospital stay for mother or neonate, malformations, or fetal weight 1.

Pregnant women should also practice good hygiene, avoid close contact with infected individuals, and consider getting the flu vaccine to minimize the risk of influenza complications. If exposed or symptomatic, they should contact a healthcare provider promptly to discuss the benefits and risks of oseltamivir treatment. The benefits of oseltamivir in reducing the severity and duration of influenza illness in pregnant women outweigh the risks, making it a recommended treatment option.

From the FDA Drug Label

1. 1 Pregnancy Risk Summary 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

The safety of Oseltamivir (Tamiflu) during pregnancy is not definitively established due to the lack of adequate and well-controlled studies. However, available epidemiological data suggest that it is not associated with an increased risk of birth defects. Considering the limitations of the studies and the potential risks, a conservative clinical decision would be to use Oseltamivir with caution in pregnant women, weighing the benefits against the potential risks, especially in cases where the mother is at high risk of severe complications from influenza 2. Key considerations include:

• The lack of adequate and well-controlled studies
• The potential benefits of Oseltamivir in preventing severe complications from influenza
• The need for careful monitoring and management of pregnant women taking Oseltamivir.

From the Research

Safety of Oseltamivir During Pregnancy

• The safety of oseltamivir (Tamiflu) during pregnancy has been evaluated in several studies 3, 4, 5, 6, 7.
• According to a review of preclinical and clinical data, oseltamivir is unlikely to cause adverse pregnancy or fetal outcomes, but available data are limited 4.
• Animal and toxicology studies do not suggest that clinically effective dosages of oseltamivir have the potential to produce adverse effects on fetal development 4.
• A study of 232 maternal exposures to oseltamivir found that the incidence of adverse pregnancy outcomes, such as spontaneous abortions and pre-term deliveries, was not higher than background incidence rates 4.
• The American College of Obstetricians and Gynecologists (ACOG) recommends that pregnant women with suspected or confirmed influenza receive antiviral treatment with oseltamivir or zanamivir, regardless of vaccination status 5, 6.
• Treatment with oseltamivir is recommended within 48 hours of the onset of symptoms, but should not be withheld if the ideal window is missed 5, 6.

Pharmacokinetics and Pharmacodynamics

• The physiologic adaptations of pregnancy may alter the pharmacokinetics and pharmacodynamics of oseltamivir 3, 7.
• Evidence of these alterations, knowledge gaps, and future investigative directions to fill these knowledge gaps are highlighted in several studies 3, 7.

Clinical Guidelines

• The Centers for Disease Control and Prevention (CDC) advises that 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.
• Obstetrician-gynecologists and other obstetric care providers should promptly recognize the symptoms of influenza, adequately assess severity, and readily prescribe safe and effective antiviral therapy for pregnant women with suspected or confirmed influenza 5, 6.