The U.S. Food and Drug Administration (FDA) has approved children-friendly tablet formulations of two commonly used antiretrovirals: Ziagen (abacavir) and Prezista (darunavir). According to separate announcements released by the agency on December 18 and 19, respectively, the protease inhibitor Prezista is now available in a 75 mg tablet for children between 6 and 18 years old and a scored 300 mg tablet of the nucleoside reverse transcriptase inhibitor Ziagen can used to treat children weighing more than 31 pounds (14 kg).

Prezista dosing for children, using the 75 mg tablets, should be based on body weight. Children between 44 and 66 pounds should take five Prezista tablets (375 mg) plus 50 mg of Norvir (ritonavir) liquid, twice a day. Children between 66 and 88 pounds should take six Prezista tablets (405 mg) plus 60 mg of Norvir liquid, twice a day. Children weighing 88 pounds or more should take the adult doses of both medications: eight 75 mg pediatric tablets or one 600 mg adult tablet plus 100 mg Norvir liquid or single tablet, twice a day.

Ziagen dosing, using the scored tablets, is also based on body weight. Children weighing 31 to 46 pounds should take half a Ziagen tablet in the morning and half a Ziagen tablet in the evening, for a total daily dose of 300 mg. For those weighing 46 to 66 pounds, the dose should be a half tablet in the morning and a whole tablet in the evening, for a total daily dose of 450 mg. Children weighing more than 66 pounds should take the one 300 mg tablet in the morning and one 300 mg tablet in the evening, for a total daily dose of 600 mg.

A liquid version of Ziagen remains available for children as young as 3 months old who cannot swallow tablets, at a dose of 8 mg per kilogram of body weight twice a day. Prezista is only available as a tablet and should only be used by children 6 years of age and older. While adults can take both medications once-daily, twice-daily dosing is the only option approved for children.