The Food and Drug Administration (FDA) has delayed its decision regarding changes to be made in the safety instruction of popular medicines as Vyvanse and Adderall. FDA said that it will be giving a full update after the final analyses on the potential impact of stimulants ADHD drugs on the risk of heart disease and strokes were evaluated. The drugs are used to treat hyperactivity.

The current instructions for ADHD drugs convey that the misuse of them may cause sudden death and serious cardiovascular adverse events. Adderall XR carries a warning about cardiovascular risks for patient with serious heart problems.

The FDA and the federal Agency for Healthcare Research and Quality for their research analyzed health data of over 500,000 people taking ADHD meds and 1 million people who weren't. Analysts are also planning to examine about 2,000 medical charts from hundreds of different hospitals.

Beinstein analyst Jack Scannell said the result is though not definitive still it is positive for the stimulant class and for Shire.

Justin Smith at MF Global told that the study was begun in 2007 and have been monitoring for any potential change in cardiovascular risk but till now the results have been positive for stimulants.

The announcement by FDA has boosted the rate of shares in British group Shire, which makes the stimulants Vyvanse and Adderall to 1.7%.