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Long-term use of Alzheimer's disease drugs questioned

A Canadian study has suggested that cholinesterase inhibitors used to treat Alzheimer's disease (AD) may often be prescribed for too long, exposing patients to unpleasant side effects for no reason and burdening healthcare systems with extended costs.

A Canadian study has suggested that cholinesterase inhibitors used to treat Alzheimer's disease (AD) may often be prescribed for too long, exposing patients to unpleasant side effects for no reason and burdening healthcare systems with extended costs.

The study, which was performed by the Institute of Clinical Evaluative Sciences (ICES) and led by Dr Nathan Hermann of the psychiatry division at Toronto's Sunnybrook Health Sciences Centre, found that more than a third of patients enrolled on the study were also taking other drugs which negated any positive effects from AD drugs.

While taking cholinesterase inhibitors, patients experience typical side effects of loose bowels and nausea. Other possible side effects include a slowed heartbeat and fainting spells. The drugs are considered to have modest clinical benefits for mild-to-moderate AD cases, although some scientists question this.

Scientists generally believe cholinesterase inhibitors work by slowing the breakdown in the brain of a chemical considered to be important for learning and memory. Use of the drugs has increased 15 times between 1999 and 2002 in Ontario, according to ICES researchers. Sales across Canada have doubled since then, racking up CAD 168m in FY06, according to IMS Health Canada. Much of that cost is covered by provincial drug plans that subsidise medication for the elderly.

The ICES' examination of patient databases found the average AD patient took a cholinesterase inhibitor for more than two years, when the disease was at its most severe. Most clinical trials have only tracked the drugs' use over only three to six months, say the researchers.

The study, which was published in the Journal of the American Geriatric Society, is not proof the drugs are being used inappropriately, but raises questions and concerns, the authors stress.

Hermann said : "We're using these drugs much longer than they've ever been studied for and we're using them longer than they are used in other locations. Are we really sure these drugs are helpful? Just because they're being treated this length of time doesn't necessarily mean we're getting significant benefit from these drugs. We also don't know if long-term use may be harmful in some way."

Dr Paula Rochon of ICES added: "I think it's important that doctors consider monitoring on a regular basis to make sure the benefit is still there, and the benefit continues to outweigh the potential risk."

"Most physicians will take patients off the drugs if they notice the person's condition is deteriorating and they are no longer benefiting from the medication," said Dr Jack Diamond, a scientific advisor to the Alzheimer's Society of Canada.

There was evidence, meanwhile, which would explain why the drugs might be effective for longer than previously thought. New research suggested the drugs also have a neuroprotective function, shielding nerves from toxic agents like those found in AD, Diamond added.

Other AD market information
A 2007 Datamonitor survey shows that AD symptomatic improvement is still a high priority in the UK, indicating that neurologists would welcome a new non-disease modifying drug, if it were differentiated from the current cognitive enhancers on efficacy or side effects. In order to achieve this in the minds of neurologists, an alternative mode of action is required.

Datamonitor forecasts that Neurochem's Alzhemed (tramiprostate) and Myriad Pharmaceutical's Flurizan (flurbiprofen), currently in clinical trials, will not necessarily threaten the acetylcholine esterase inhibitor (AEI) market. Treatment with AEI drugs will extend the therapeutic window for symptomatic drugs, resulting in an opportunity for key players in this market.

Datamonitor also believes that the recently published NICE guidelines will only have a modest impact on AD disease drug sales in the UK. From looking at survey reported current prescribing trends and relating this to adherence with previous NICE AD drug guidelines, prescribers do not appear to guideline-prescribe.

In the US, France, Germany, Italy, Spain, the UK and Japan there are 16m AD patients, a number which is expected to grow to 21m by 2010. It is also the eighth leading cause of death in the US and once diagnosed, the average life span of an AD patient is eight years. The AD market in these regions was worth USD 6.1bn in 2005 and will increase to USD 7.8bn by 2010.

The main marketed cholinesterase inhibitors for mild-to-moderate AD are Novartis' Exelon (rivastigmine), Eisai's Aricept (donepezil) and OrthoMcNeil's Razadyne (galantamine). An approved drug for moderate-to-severe AD is Forest Labs' Namenda (memantine).

30th September 2008


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