A drug used to treat skin infections including Athlete's Foot could help to slow the progression of Alzheimer's disease, scientists say.
Both strokes and Alzheimer's affect the brain
A team at University College London said tests of Clioquinol on 36 patients were "encouraging".
Their disease was shown to develop less quickly than those given a dummy pill.
A second study in the journal Archives of Neurology found stroke patients are at an increased risk of developing Alzheimer's.
In Alzheimer's disease, protein deposits called amyloid plaques form which impede and kill nerves in the brain. The plaques need zinc for the proteins to clump together.
Clioquinol, which has antibacterial and antifungal properties, is used as an ointment to treat skin infections, but it also binds metal atoms.
When it is taken as a pill form it can enter the brain from the bloodstream and bind to zinc, removing any which is already bound to the amyloid, and collecting up any dangerous free zinc.
In the University College London research, 36 patients with mild to moderate Alzheimer's were studied.
They were assessed to see how their disease had affected cognitive abilities such as memory, orientation, language, attention and reasoning.
Alzheimer's is assessed using a scale ranging from 0 to 70. Lower scores indicate a healthy adult, and as dementia progresses, the score increases.
Eighteen of the patients were given Clioquinol, while the rest were given a dummy version.
Those with the highest scores at the start of the study showed an average increase of 1.5 points at 24 weeks, compared to around 8.9 points for those on the dummy pill.
Experts say a change of four points is clinically significant.
Dr Craig Ritchie, director of clinical studies at University College London, said: "The results of this trial have been very encouraging.
"We are now planning further testing using Clioquinol in a larger, multi-centre study which is seeking public funding."
In a second study, researchers from Columbia University in New York found people who had suffered a stroke were at an increased risk for developing Alzheimer's, especially if they also have cardiovascular disease.
Both diseases are common among the elderly, but scientists have been unable to discover how they are linked.
Over 1,760 patients over 65 were studied from 1992 to 1999. They were asked about a history of stroke in their family and whether they already had cardiovascular disease.
It was found patients with stroke were around 60% more likely to develop Alzheimer's than those who had never had a stroke.
The annual incidence of Alzheimer's Disease was 5.2% among patients with stroke, and 4% for patients without.
Dr Robert Mayeux, who led the research, said the link may be explained by damage to the blood vessels, increasing the risk of stroke, and denying the brain a proper supply of nutrients.
Alternatively, a stroke might cause damage to the brain that makes Alzheimer's more likely.
A spokeswoman for the UK's Alzheimer's Society said both pieces of research were of interest.
Dr Susanne Sorensen, head of research, said: "The results of the UCL research may be a novel use for this already existing drug in the treatment of Alzheimer's disease.
"But the trial is limited in its scale and we believe it would be valuable to see a larger scale trial.
"The potential for new drugs that may interfere with or revert the progression of Alzheimer's disease gives hope to people with dementia and their carers.
"There are currently only limited and expensive treatment options available for Alzheimer's disease and none that revert the disease for more than a short period."
She added: "The Columbia research is further evidence that there are links between Alzheimer's and stroke.
"It also underlines the potential for preventative approaches in stroke and vascular disease, which in turn would minimise the incidence of Alzheimer's disease.
"This includes minimising the amount of salt and saturated fat we eat and avoiding those risk factors that increase our chance of stroke."