The U.S. drugs regulator said it was not recommending changes in the use of stimulants such as Adderall XR and Ritalin to treat hyperactivity, after a review of a study into potential heart disease risks from the drugs.

"At this time, FDA is not recommending any changes to the drug labels and or use of these medications," the U.S. Food and Drug Administration said on its website.

The FDA said it would give a full update after the final analyses on the potential impact of stimulant ADHD drugs on the risk of heart disease and strokes were evaluated.

Shares in British group Shire, which makes the stimulant Vyvanse as well as Adderall XR, rose 1.7 percent after analysts said the update clearly suggested the FDA had seen no obvious safety signals in the study.

"While not absolutely definitive, this is positive for the stimulant class and for Shire," Beinstein analyst Jack Scannell said. "Concerns over the possibility of a bad outcome have curbed our enthusiasm for Shire."

Justin Smith at MF Global said the news was unsurprising, as rigorous monitoring for any potential change in cardiovascular risk had been in place since the study started in 2007, but was still positive for sentiment.

Adderall XR carries a warning about cardiovascular risks for patient with serious heart problems, and doctors generally assess a patient's cardiovascular history before starting treatment.