Drug withdrawal shocks Shire

UK company Shire has moved to allay fears that one of its top-selling drugs, Adderall XR, may be responsible for sudden deaths in patients with heart conditions.

The drug, used to treat attention deficit hyperactivity disorder (ADHD), was suspended from the Canadian market last week after the regulators linked it with 20 deaths - of which 14 were children - since it first hit the market in 1994.

The decision by Health Canada has put more pressure on the US Food and Drug Administration, which has faced recent criticism over its handling of drug safety issues such as Vioxx and Celebrex.

Shire chief executive Matthew Emmens said the company strongly disagreed with the decision, which had come as “an absolute surprise”. He admitted that when Health Canada requested Shire voluntarily to withdraw the drug from the market, the company refused.

Yet, he didn't expect the regulator to then take action to suspend the drug indefinitely, particularly as the US FDA had reviewed the same information but seen fit only to enforce a label change.

The FDA stopped short of suspending the drug, merely warning that people with heart conditions should not take Adderall, and suggesting that studies may be done in the future to determine whether it raises risks in other patients.

“Such deaths are extremely rare, and it's hard to tell in any given case if it happens with the drug or just occurs spontaneously,” said Robert Temple, director of the office of medical policy at the FDA's drug centre.

Republican senator for Iowa, Charles Grassley was quoted in the New York Times as saying he had been informed that the FDA had asked Health Canada not to suspend the drug because it did not want another drug safety crisis.

The FDA has denied the allegation.

Emmens added that he did not expect Health Canada's decision to have a significant spill-over effect in the US, where sales of Adderall amassed to £393m ($700m) last year, accounting for about 50 per cent of the firm's total drug sales.

Shire has pointed out that most of the deaths had already been reported in the original dossiers the Basingstoke-based company submitted to Health Canada for approval, which it duly granted in February 2004.

Although shares in the firm dropped by as much as 16 per cent on the news, some analysts said the decision would not have a significant effect on the company's performance.

“We think the Canadian action should be seen more as a storm in a teacup than a major threat to Shire,” said Frances Cloud, pharma analyst at Nomura.