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Pharmacokinetics of Antiviral Agents for Seasonal Influenza
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 absorbed systemically. 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.
NOTE: The text above is taken from Prevention & Control of Influenza - Recommendations of the Advisory Committee on Immunization Practices (ACIP) 2008. MMWR 2008 Jul 17; Early Release:1-60. (Also available as PDF, 586K).
- Page last updated August 29, 2008
- Content Source: Coordinating Center for Infectious Diseases (CCID)
- National Center for Immunization and Respiratory Diseases (NCIRD)
