San Francisco, CA, May 21, 2003 Shire Pharmaceuticals Group plc (NASDAQ: SHPGY, LSE: SHP.L, TSE: SHQ CN) announced results of a long-term clinical trial that showed significant improvements in symptom control and quality of life in children with attention-deficit/hyperactivity disorder (ADHD) with continued, long-term treatment (two-year) using a once-daily mixed salts amphetamine product. Moreover, these children sustained improvement in ADHD symptoms of at least 35 percent throughout the study. This information was presented today at the American Psychiatric Association (APA) annual meeting.

ADHD is the most commonly diagnosed psychiatric disorder in children and adolescents. Approximately two million U.S. children, three to seven percent of all school-aged children, have been diagnosed with ADHD. The disorder is characterized by symptoms of inattention, impulsiveness and hyperactive behavior.

"ADHD is an all-day disorder that requires treatment to manage symptoms at home, in school, and in socials settings. Our study shows that long-term treatment with a once-daily mixed salts amphetamine product remains effective in significantly controlling the symptoms of ADHD in children, which is very reassuring to health care providers and parents," said James McGough, M.D., associate professor, UCLA Neuropsychiatric Institute.

Long-Term Safety and Efficacy of Once-Daily Mixed Salts Amphetamine Product in Children With ADHD (APA Presentation Session #21) Prior to this two-year extension trial, 560 children had participated in one of two short-term clinical trials (three to four weeks) of the same medication. Results from the two-year study showed that, on average, the children achieved and maintained a significant improvement of at least 35 percent (compared to at the beginning of the study) in t
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Contact: Michle Roy, Shire Pharmaceuticals Group plc
450-978-7938
Porter Novelli
21-May-2003