Pharmacokinetics of oseltamivir in infants under the age of 1 year.
BACKGROUND
Oseltamivir is the only antiviral treatment recommended for influenza in young children over the age of 1 year. There is scant data on oseltamivir pharmacokinetics (PK) in infants <1 year. We set out to perform PK measurements in infants who received oseltamivir.


METHODS
This study was a prospective, uncontrolled, open label evaluation of the pharmacokinetics of oseltamivir metabolism, safety of oseltamivir, viral clearance in infants <12 months diagnosed with influenza by nasopharyngeal influenza nucleic acid antigen test (NAAT). Blood levels of the prodrug oseltamivir and its active carboxylate were measured prior to a dose of oseltamivir and at 4 time points afterwards, to calculate Cmax (ng/mL), Tmax (h), AUC0-t (ng h/mL) and time for AUC (h).


RESULTS
Four children with influenza A received oral oseltamivir, 2.35-3 mg/kg/dose. This dose range produced a target oseltamivir carboxylate plasma concentration in excess of the proposed 12-h target AUC of 3800 ng h/mL, selected from earlier studies to avert resistance. One patient developed GIT adverse event: dry retching.


CONCLUSIONS
Oseltamivir was well tolerated at a dose of 2.35-3 mg/kg/dose twice a day in infants under the age of 1 year. In general agreement with earlier data, these doses produced a target oseltamivir carboxylate plasma exposure in excess of the proposed 12-h target exposure of AUC equal to 3800 ng h/mL in two patients. The limited plasma concentration data in the remaining two patients were not inconsistent with the target exposure being reached.
The Children's Hospital, Westmead, Sydney, Australia. rashmid@uni.sydney.edu.au.|The University of Sydney, Sydney, Australia. rashmid@uni.sydney.edu.au.
Rashmi
R
Dixit
The University of Sydney, Sydney, Australia.
Slade
S
Matthews
The Children's Hospital, Westmead, Sydney, Australia.
Gulam
G
Khandaker
The Children's Hospital, Westmead, Sydney, Australia.|The University of Sydney, Sydney, Australia.
Karen
K
Walker
The Children's Hospital, Westmead, Sydney, Australia.|The University of Sydney, Sydney, Australia.
Marino
M
Festa
The Children's Hospital, Westmead, Sydney, Australia.|The University of Sydney, Sydney, Australia.
Robert
R
Booy
Infants; Influenza; Oseltamivir; Paediatrics