An FDA study found that 25 people died suddenly and 54 others suffered serious unexplained heart problems while taking attention deficit hyperactivity disorder (ADHD) drugs like Novartis’ Ritalin from 1999 to 2003, according to news reports published today. An FDA advisory committee was scheduled to meet Thursday to discuss the data and recommend ways to research whether the drugs are to blame for the deaths. In 2004, approximately 29 million prescriptions were written for Ritalin, Shire’s Adderall and similar drugs.Reports of 20 sudden deaths, 12 among children, prompted Canadian health officials to halt sales of Adderall XR last February. After studying the issue, Canadian authorities allowed the drug back on the market in August.