UK drug giant GlaxoSmithKline has added stronger warnings to the label of its attention-deficit hyperactivity and narcolepsy drug Dexedrine (dextroamphetamine), alerting doctors and patients that “misuse of amphetamines may cause sudden death and serious cardiovascular adverse events,” and detailing an increased risk of heart problems and psychiatric side effects.

In a letter to healthcare professionals, posted on the US Food and Drug Administration’s website, GSK said its move was spurred by a request from regulators that all makers of central nervous system stimulant drugs approved to treat ADHD update the prescribing information on their products with such “additional, standardised language.”

The agency’s alleged request to revise the labelling of this group of drugs, which includes Novartis Ritalin (methylphenidate) and Shire’s Adderall (mixed amphetamine salts), was driven by separate recommendations from two of its advisory panels.

In March this year, one advisory committee recommended that new warnings be added to the labelling of drugs for ADHD to draw attention to the risk of potential adverse reactions, but stopped short of recommending a 'black-box' warning - the strongest available on medicine labelling - for fear of alarming patients and preventing those who could benefit from the products from receiving treatment.

But this was in direct contrast to an earlier panel recommendation, which voted in favour of adding a black-box warning to some ADHD products.

Use of ADHD products rose 19% among people aged 20 to 44 last year, to 1.7 million, while there was a 2% increase in usage among people aged 19 or younger to 3.3 million, according to just-published data from Medco Health Solutions. But use in younger children (aged two to 10) fell 5%, and this is thought to be related to press coverage of the ongoing debate into the products' safety.