When Aricept, a new "wonder drug" to tackle Alzheimer's disease, was launched in April, reactions were mixed. Doctors involved in trials of the drug were enthusiastic, those from the Alzheimer's Disease Society were sceptical about its effectiveness, warning it was akin to "using an aspirin to treat a brain tumour", while the health service worried about the cost, potentially pounds 200m a year.

A backstage battle has been raging ever since between cost-conscious health authorities (the drug would cost pounds 1,000 per patient per year), a politically sensitive Department of Health and the manufacturer, terrified that failure in the UK market may affect worldwide sales. The Government is currently grappling with new national guidance on prescribing the drug; meanwhile families and friends of those with Alzheimer's are wondering if Aricept is the answer. Aricept works by preventing the breakdown of a neurotransmitter in the brain, acetylcholine, which seems to be deficient in Alzheimer's patients. The manufacturers, a Japanese company called Eisai, says it can delay progress of the disease by six months and could therefore reduce the numbers of elderly people with Alzheimer's needing residential care. But Aricept does not actually stop progress of the disease: it just puts off the onset of the crippling symptoms. It can temporarily ease the problems, but it is not a cure.

In addition, Aricept works only for Alzheimer's; it is not effective for other forms of dementia. Alzheimer's affects around 5 per cent of the population under 60. Early symptoms include forgetfulness, repeating yourself and problems making decisions - symptoms common to certain other disorders. Sufferers eventually become more confused, and may not recognise their own family. The problem is that currently there is no clinical test for the disease, although a brain scan can detect changes in neurotransmitters which indicate its presence.

Eisai, which is marketing the drug in the UK through Pfizer, also make it clear that Aricept can only help people with mild to moderate forms of Alzheimer's disease. That in itself is a minefield. Only a hospital consultant qualified in old age psychiatry would be able to decide whether the disease was still at a stage when Aricept could help.

Two trials, of three and six months' duration, were carried out in the States during 1996 before the drug gained a licence. A third post-licensing trial in Europe was over six months. The US trials were each of 450 patients: a third on 5mg Aricept, a third on 10mg; and the rest on a placebo.

Two different tests were carried out of cognitive abilities, such as ability to recall words and copy simple drawings, along with a general assessment by a clinician partly based on the carer's view of how a patient was coping.

The US researchers found patients on Aricept improved four points on the scale used to measure cognitive performance, compared with the normal deterioration of four points over a similar period. However, a recent report from Dr Ken Stein of the Wessex Institute for Health Research concludes the clinical significance of this was "uncertain" and that "no definite changes in disability or quality of life have been demonstrated". The clinical assessments showed only minimal change and used a scale which was not reliably established, Dr Stein adds.

There is no research into Aricept's effect on people with severe Alzheimer's who are considered unlikely to benefit from the drug. People living alone are also unlikely to benefit as they may forget to take the daily dose. So its use will probably be limited to people with a carer who can ensure compliance.

Although safe enough to be licensed, side effects can include diarrhoea, nausea and vomiting, insomnia, fatigue and anorexia. The manufacturers also warn against prescribing to people with other conditions including asthma and lung disease.

Even if you decide you want the drug, you may be denied it - at least, on prescription. If you live in Wirral, you may be lucky (but probably only after the patient has had a brain scan), but in Birmingham you certainly won't. A survey in June by the Alzheimer's Disease Society showed only six health authorities were prescribing Aricept, 10 were definitely not and the rest had yet to decide. As one director of public health has commented, with no research into the long-term effects, large amounts of money could be swallowed up with no clear idea of the outcome.

Which begs the next, and thorniest, question of all: having given someone Aricept initially, when do you say enough is enough, and take them off?n

Lynn Eaton

Cherrill Hicks is on holiday