So why is it that when pharmaceutical giant Johnson & Johnson brought out a drug to treat schizophrenia, the product quickly became the most widely prescribed antipsychotic in the USA, and is now the company's second most profitable drug with global sales of $2.1bn?

These heady days in the sun may suddenly come to an end for the drug, Risperdal (risperidone), after the American drugs regulator, the Food and Drug Administration, issued the sternest of warnings. The FDA pronounced that Risperdal 'has not been shown to be safe or effective in the treatment of patients with dementia-related psychosis.' Isn't dementia-related psychosis what simple folk call Alzheimer's? And isn't it the case that the drug, designed for schizophrenia, has been severely harming and even killing Alzheimer's patients? Sadly, true on both counts.

The warning has just been issued to doctors in America, and yet a similar warning had gone out to doctors in Canada at least six months earlier. In the Canadian letter, J&J cited 37 reports of stroke or stroke-like events such as blood clots and haemorrhages, which included 16 deaths. There're plenty of other reports that paint a similar grim picture.

Undaunted, J&J has been pushing through the world's licensing authorities an injectable form of the drug, known as Risperdal Consta. The Spanish authorities passed it in February, and it's already been approved in 16 other countries, including the UK and Ireland.

We're sure J&J will be issuing a warning with the drug, and will point out to doctors that there is a difference between schizophrenia and Alzheimer's.

(Sources: FDA Safety Information and the Johnson & Johnson websites).