Dosing for the antiretroviral drug Retrovir (zidovudine) for children has been expanded and revised, according to the U.S. Food and Drug Administration (FDA). Whereas the drug had formally been recommended for children six weeks and older, it can now be used in newborns who are only 4 weeks old.

The FDA prescription label revisions, issued November 10, also suggests weight-based dosing for smaller children, with doses starting at 12 milligrams (mg) per kilogram (kg) of body weight for babies weighing between 4 and 9 kg (8.8 and 19.8 lbs, respectively). Children heavier than 30 kg (66 lbs) take a 300 mg tablet, capsule or syrup twice a day.