Research showed trazodone stops brain cells dying, a hallmark of the incurable condition.
The drug has already been used to treat people suffering late-stage dementia – but it could be prescribed to patients at an early stage of the neurological disorder.
And the brain cell effect was also seen in trials of another drug called dibenzoylmethane.
An anti-depressant could become the first drug to halt dementia
The breakthroughs raise the possibility of an “off-the-shelf” treatment for dementia sufferers in as little as two years.
Dr Doug Brown, of Alzheimer’s Society, said: “We’re excited by the potential of these findings.
As one of the drugs is already available as a treatment for depression the time taken to get from the lab to the pharmacy could be dramatically reduced.”
Although trazodone is currently licensed as an anti-depressant it is being “repurposed” to assess its impact on other conditions.
We currently have no way of treating these diseases so the prospect of finding drugs that can slow or stop them from progressing is extremely exciting
It works by blocking a natural defence mechanism in cells which is overactive in the brains of people with frontotemporal dementia.
Experts hope it will be the first “disease modifying therapy” to tackle the causes of diseases like Alzheimer’s rather than mask the symptoms.
Professor Giovanna Mallucci, of the Medical Research Council and the University of Cambridge, said: “We know that trazodone is safe to use in humans so a clinical trial is now possible to test whether the protective effects of the drug we see on brain cells in mice with neurodegeneration also applies to people in the early stages of Alzheimer’s and other dementias.
“We could know in two to three years whether this approach can slow down disease progression, which would be a very exciting first step in treating these disorders.”
Researchers found trazodone, also known as Molipaxin when taken to treat major depressive disorder, protected against brain damage and shrinkage in mice.
They are hopeful the same will happen when it is tested in humans.
It works by blocking a natural defence mechanism in cells which is overactive in the brains of people with frontotemporal dementia, Alzheimer’s disease and Parkinson’s.
The same effect was seen in trials using dibenzoylmethane, a compound being tested as a cancer busting drug.