The FDA first approved Tamiflu to treat influenza in adults in 1999. It was later given the green light for children over one year of age. Now the Food and Drug Administration has just extended the accepted use of this oral medicine for babies between two weeks and 12 months old. Infants can be extremely susceptible to serious complications of influenza. Getting the dose right for such young patients can be challenging and requires special calculations by physicians and pharmacists. The primary side effects of Tamiflu are nausea, vomiting, stomachache and diarrhea. The drug can also cause some rare but very serious reactions such as anaphylaxis, liver problems and the potentially life-threatening skin reaction called Stevens-Johnson syndrome.