CDC updates proposed treatment course for swine flu

ATLANTA The Centers for Disease Control and Prevention on Tuesday updated its proposed treatment course for any patient expected of having been exposed to the swine flu.

Either Tamiflu (oseltamivir) or Relenza (zanamivir) are recommended for up to 10 days after the last known exposure to a confirmed case of swine influenza A (H1N1) virus infection.

For pre-exposure protection, antivirals should be given during the potential exposure period and continued for 10 days after the last known exposure to a confirmed case of swine influenza A (H1N1) virus infection.

Antiviral used as a preventitive (pre-exposure or post-exposure) with either oseltamivir or zanamivir is recommended for the following individuals:

• Household close contacts who are at high-risk for complications of influenza (e.g., persons with certain chronic medical conditions, persons 65 or older, children younger than 5 years old and pregnant women) of a confirmed, probable or suspected case;
• School children who are at high-risk for complications of influenza (children with certain chronic medical conditions) who had close contact (face-to-face) with a confirmed, probable or suspected case;
• Travelers to Mexico who are at high-risk for complications of influenza (e.g., persons with certain chronic medical conditions, persons 65 or older, children younger than 5 years old and pregnant women);
• Healthcare workers or public health workers who were not using appropriate personal protective equipment during close contact with an ill confirmed, probable or suspect case of swine influenza A (H1N1) virus infection during the case’s infectious period.

Pre-exposure antiviral used as a preventatitive with either oseltamivir or zanamivir can be considered for the following:

• Any health care worker who is at high-risk for complications of influenza (e.g., persons with certain chronic medical conditions, persons 65 or older, children younger than 5 years old and pregnant women) who is working in an area of the healthcare facility that contains patients with confirmed swine influenza A (H1N1) cases, or who is caring for patients with any acute feverish respiratory illness;
• Non-high risk persons who are travelers to Mexico, first responders or border workers who are working in areas with confirmed cases of swine influenza A (H1N1) virus infection.

Children under one year of age are at high risk for complications from seasonal human influenza virus infections. The characteristics of human infections with swine H1N1 viruses are still being studied, and it is not known whether infants are at higher risk for complications associated with swine H1N1 infection compared to older children and adults. Limited safety data on the use of oseltamivir (or zanamivir) are available from children less than one year of age, and oseltamivir is not licensed for use in children less than 1 year of age. Available data come from use of oseltamivir for treatment of seasonal influenza. These data suggest that severe adverse events are rare, and the Infectious Diseases Society of America recently noted, with regard to use of oseltamivir in children young than one-year-old with seasonal influenza, that “…limited retrospective data on the safety and efficacy of oseltamivir in this young age group have not demonstrated age-specific drug-attributable toxicities to date.”

Because infants typically have high rates of morbidity and mortality from influenza, infants with swine influenza A (H1N1) influenza infections may benefit from treatment using oseltamivir.

Healthcare providers should be aware of the lack of data on safety and dosing when considering oseltamivir use in a seriously ill young infant with confirmed swine H1N1 influenza or who has been exposed to a confirmed swine H1N1 case, and carefully monitor infants for adverse events when oseltamivir is used.

Oseltamivir and zanamivir are “Pregnancy Category C” medications, indicating that no clinical studies have been conducted to assess the safety of these medications for pregnant women. Because of the unknown effects of influenza antiviral drugs on pregnant women and their fetuses, oseltamivir or zanamivir should be used during pregnancy only if the potential benefit justifies the potential risk to the embryo or fetus; the manufacturers' package inserts should be consulted. However, no adverse effects have been reported among women who received oseltamivir or zanamivir during pregnancy or among infants born to women who have received oseltamivir or zanamivir, Pregnancy should not be considered a contraindication to oseltamivir or zanamivir use. Because zanamivir is an inhaled medication and has less systemic absorption, some experts prefer zanamivir over oseltamivir for use in pregnant women when feasible.