Three judges found that the process by which the National Institute for Health and Clinical Excellence (Nice) decided to restrict the anti-dementia medicines for newly diagnosed patients with mild Alzheimer's was procedurally unfair.

Eisai, licence holder of Aricept, and Pfizer, which challenged the Nice decision, said the ruling brought renewed hope for Alzheimer's patients.

The judges said procedural fairness demanded that Nice should release a full version of the cost-effectiveness model it used to produce guidance for the form of treatment.

They invited Nice to make a new determination after the drugs companies make representations when they have studied the guidance model.

Nick Burgin, managing director of Eisai, commenting on the judgment, said: "We believe that this decision represents a victory for common sense. As soon as we have reviewed their cost-effectiveness calculations we will submit any new findings to Nice.

"We hope that this action will ultimately restore access to anti-dementia medicines for those patients at the mild stages of Alzheimer's disease."

David Pannick QC, representing Eisai, told the Court of Appeal at a hearing last month that the guidance ruling by Nice would have "a very substantial effect upon the availability and the potential duration of treatment" with the drugs.

Nice had ruled that the drugs are not cost-effective for patients in the early stages of Alzheimer's - a decision upheld by the High Court last year.

Nice had decided in 2004 that the drugs, which cost about £2.50 a day, did not make enough of a difference to recommend them for all patients.