The Food and Drug Administration approved Vyvanse, also known as lisdexamfetamine, agency spokeswoman Susan Cruzan said. The drug is made by Shire PLC. Shire hopes the drug will extend its lucrative ADHD franchise once its top-selling Adderall XR begins facing competition from lower-priced generic versions in 2009. Shire plans to move patients from the older to the newer drug at the time, company spokesman Matt Cabrey said this week.

Shire said it tried to limit the drug’s potential for misuse. It tested the drug on adults with a history of abusing stimulants to assess its “likeability.” Results suggest the drug delays the onset and limits the intensity of amphetamine-like effects, the company said.

Vyvanse works by gradually releasing its active ingredient, d-amphetamine, after the drug has been swallowed and comes into contact with enzymes in the digestive tract.

Unless it’s swallowed, Vyvanse remains inactive. Shire believes that will curtail its potential for abuse by users who snort or inject crushed pills.

Despite those measures, the Drug Enforcement Administration has proposed making Vyvanse a Schedule II drug, a class that includes cocaine, methadone, methamphetamine and other drugs with a high potential for abuse.

Other ADHD medicines, including Adderall and Ritalin, also are Schedule II drugs.

Vyvanse’s label will bear a “black-box” warning, the government’s strongest, Cruzan said. Details were not immediately available.

The label of Adderall XR bears a warning because of safety concerns related to amphetamine abuse as well as the risk of sudden death in patients with heart defects.

FDA approval of Vyvanse came the same week that the agency asked all manufacturers of ADHD drugs to warn patients and their parents of mental and heart problems associated with use of the medicines.

Britain’s Shire said earlier this month it would spend roughly $2.6 billion to buy New River Pharmaceuticals Inc., the Radford, Va., company that originally developed Vyvanse.