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Pharmacokinetics of Antiviral Agents for Seasonal Influenza
NOTE: This information is taken from “Prevention and Control of Influenza Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2007” (MMWR 2007 Jul 13:5[RR06];1-54) and focuses on the two licensed influenza antiviral agents recommended for use in the United States during the 2007-08 influenza season: oseltamivir and zanamivir.
Zanamivir
In studies of healthy volunteers, approximately 7%–21% of the orally inhaled zanamivir dose reached the lungs, and 70%–87% was deposited in the oropharynx. Approximately 4%–17% of the total amount of orally inhaled zanamivir is systemically absorbed. Systemically absorbed zanamivir has a half-life of 2.5–5.1 hours and is excreted unchanged in the urine. Unabsorbed drug is excreted in the feces.
Oseltamivir
Approximately 80% of orally administered oseltamivir is absorbed systemically. Absorbed oseltamivir is metabolized to oseltamivir carboxylate, the active neuraminidase inhibitor, primarily by hepatic esterases. Oseltamivir carboxylate has a half-life of 6–10 hours and is excreted in the urine by glomerular filtration and tubular secretion via the anionic pathway. Unmetabolized oseltamivir also is excreted in the urine by glomerular filtration and tubular secretion.
- Page last updated September 26, 2007
- Content Source: Coordinating Center for Infectious Diseases (CCID)
- National Center for Immunization and Respiratory Diseases (NCIRD)
