Britain’s Shire Pharmaceuticals said on Thursday that Canada has requested the suspension of sales of its attention deficit hyperactivity disorder treatment, Adderall XR (dextroamphetamine), because of safety concerns.

In a statement the company said it was complying with the request but “strongly disagreed” with the decision of the Canadian regulator, Health Canada, which was based on its interpretation of adverse event data during a routine label update.

Health Canada said in a statement it had suspended the market authorization of the product “due to safety information concerning the association of sudden deaths, heart-related deaths, and strokes in children and adults taking usual recommended doses of Adderall and Adderall XR

“Health Canada’s decision comes as a result of a thorough review of safety information provided by the manufacturer, which indicated there were 20 international reports of sudden death in patients taking either Adderall or Adderall XR.

“These deaths were not associated with overdose, misuse or abuse. Fourteen deaths occurred in children, and 6 deaths in adults. There were 12 reports of stroke, 2 of which occurred in children.

“A preliminary review of safety data for the other related stimulants authorised for use in the treatment of ADHD in Canada has been conducted. In that review, the incidence of serious adverse reactions leading to death was higher in Adderall and Adderall XR combined than in the other drugs of this class.

“Health Canada has asked manufacturers of other related stimulants approved for the treatment of ADHD to provide a thorough review of their worldwide safety data.”

A Shire spokeswoman told APM that the 20 deaths were reported over a 10-year period during which time more than one million people had taken 37 million prescriptions of Adderall and Adderall XR.

The company stressed that its product remains on sale in the United States, even though the same data were reviewed by the Food and Drug Administration.

“The interpretation of the same data by the US FDA led to a revised US label for Adderall XR in September 2004, clarifying that the drug generally should not be used in children or adults with structural cardiac abnormalities,” it said.

Matthew Emmens, Chief Executive Officer, commented: “We are surprised by this action from Health Canada. Shire remains confident in the safety and efficacy of Adderall XR.”

Adderall XR was approved by Health Canada in January 2004. Approximately 11,000 patients are taking the drug in Canada. Sales were around US $10 million in its first year on the Canadian market.