Oseltamivir: A New Option for the Management of Influenza in Children

Marcia L. Buck, Pharm.D., FCCP

Pediatr Pharm. 2001;7(2) 

In This Article

Pharmacokinetics

Oseltamivir phosphate is readily absorbed from the gastrointestinal tract, with approximately 80% bioavailability. The prodrug is extensively converted to active oseltamivir carboxylate by hepatic esterases; less than 5% of a dose is eliminated unchanged. Administration with food does not appear to affect overall absorption, but may slightly delay time to maximum serum concentration of the active compound.[4,5,7]

Oseltamivir is well distributed to the nasal mucosa, the tracheal lining, and the tissues of the middle ear. In adults, the volume of distribution for oseltamivir carboxylate has ranged from 23 to 27 L. There are currently no data available in children. Neither the prodrug or the active form are highly protein bound.

Oseltamivir carboxylate is eliminated by glomerular filtration and renal tubular excretion without further metabolism. The average half-life of elimination in adults is 6-10 hours. It is recommended that the dosing frequency be reduced from twice to once daily for treatment and from once daily to every other day for prophylaxis in patients with moderate renal dysfunction (creatinine clearance 10-30 ml/min). Dosing has not been established in patients with renal failure.[4,5,7]

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