A drug that was once used as an antihistamine by people with allergies in Russia offers new hope for Alzheimer's patients, a study published today suggests.

The drug, dimebon, has so far been trialled on only 183 patients, but it led to significant improvement in the understanding and behaviour of patients with mild to moderate Alzheimer's disease, according to the research published in the Lancet medical journal.

Treatments for Alzheimer's are badly needed. Those that exist are controversial; arguments rage over whether or not Aricept and similar drugs work well enough to be worth their high cost.

The dimebon trial took place in Russia, where the drug has dropped out of use in allergy treatment as newer drugs have been discovered. The 183 patients from 11 different sites were randomly divided into two groups and given either dimebon three times a day or a placebo.

The team, led by Dr Rachelle Doody from Baylor College of Medicine in Houston, found those on the drug were better aware and able to carry out tasks. The improvements were maintained and even improved over 12 months, which no Alzheimer's drugs have succeeded in doing so far.

A bigger trial, which will establish whether the drug really is a useful treatment for most people with Alzheimer's, has been announced.