In the UK the country's watchdog for cost-effectiveness in medical treatments, the National Institute for Health and Clinical Excellence (NICE), has asked drug makers for more evidence about the benefits of their Alzheimer's medicines.
The move has served to prolong a bitter row over whether the drugs should be paid for by the state.
NICE says it believes the drugs should not be prescribed routinely, but do admit that there might be a sub-group of patients for whom the pills work particularly well.
The future of the four drugs is now undecided, including Pfizer and Eisai's market leading product Aricept, which are currently available on the state health service and are widely used around the world.
According to Clive Ballard, director of research at the Alzheimer's Society, although the drugs do not work for everyone, they can improve memory and delay the progression of Alzheimer's by up to 12 months.
NICE's failure to back the drugs says Ballard is "outrageous" and its request for more information on effectiveness, pointless, as the drugs have already been assessed in more than 30 clinical trials.
Back in March NICE issued a draft proposal recommending users of the four drugs should no longer be reimbursed on the National Health Service because they were not sufficiently cost effective.
If the draft proposal is confirmed, manufacturers are concerned that this will deter other health authorities from using the drugs.
The drugs cost around 1,000 pounds per patient each year.
Also affected are Reminyl, from Johnson & Johnson and Shire Pharmaceuticals, and Novartis' Exelon, both of which are used like Aricept to treat mild to moderate Alzheimer's.