Oseltamivir (Tamiflu®, Roche) was recently licensed for the treatment of uncomplicated illness due to influenza infections in children 1 year of age and older who have been symptomatic for no more than 2 days. It has been licensed for use in adults since October 2000. We highlight the findings of a recent preclinical study which alerts to the potential concerns pertaining to the use of Tamiflu® in very young children.
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New preclinical findings
Roche has recently released the findings from its preclinical study carried out in juvenile rats
(7-day old) and highlighted the concerns to the regulatory authorities regarding the use of Tamiflu® in infants. Juvenile rats that were treated with a single dose of 1000 mg/kg oseltamivir (about 250 times the recommended total daily dose) died due to the unusually high levels of oseltamivir and its phosphate salt found in the brain of these young animals. The concentrations of oseltamivir phosphate were approximately 1,500 times those seen in adult rats given the same dose. It is likely that these high exposures are related to an immature blood brain barrier of the juvenile rats.
Studies showed no death or other significant effects in older juvenile rats given the same or higher doses of Tamiflu®.
(7-day old) and highlighted the concerns to the regulatory authorities regarding the use of Tamiflu® in infants. Juvenile rats that were treated with a single dose of 1000 mg/kg oseltamivir (about 250 times the recommended total daily dose) died due to the unusually high levels of oseltamivir and its phosphate salt found in the brain of these young animals. The concentrations of oseltamivir phosphate were approximately 1,500 times those seen in adult rats given the same dose. It is likely that these high exposures are related to an immature blood brain barrier of the juvenile rats.
Studies showed no death or other significant effects in older juvenile rats given the same or higher doses of Tamiflu®.
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HSA’s recommendation / action
The clinical significance of these data to human infants is uncertain. Due to the uncertainty in predicting the exposures in infants with immature blood brain barrier, prescribers are advised that Tamiflu® should not be given to children under 1 year of age. The above findings have been included in the package insert of Tamiflu®.
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