Medications used to treat hypertension, diabetes and skin conditions could also treat dementia, according to new research.
The study by King's College London identified four existing drugs and one drug class which could reduce the risk or slow down symptoms of the disease.
The Alzheimer's Society, which funded the research, said the use of drugs already available could be a cheaper and quicker way of tackling dementia.
But the charity admitted more work was needed to understand how the drugs could work for sufferers.
New report suggests existing medications could also treat dementia
The report's lead author, Professor Clive Ballard, who represents King's College London and the Alzheimer's Society, said: "Defeating dementia is one of the biggest challenges facing both medicine and society as a whole.
"Developing new drugs to treat the condition is incredibly important, but comes with a huge price tag and, for those affected by dementia, an unimaginable wait.
"This study identifies existing treatments and shows the potential to identify other similar drugs which are safe and if effective in clinical trials could be used to treat Alzheimer's disease in 10 years or less. We are urgently working to take this work forward to start making a difference to the lives of people with dementia."
The report concluded that there was "strong evidence regarding the potential value" of calcium channel blockers substantially reducing the risk of dementia.
Dr Ann Johnson, 59, from Manchester, who lives with Alzheimer's disease, said: "Access to drug treatments has made a huge difference to my life.
"Before I was prescribed them I knew what I wanted to say but I couldn't find the right words. I had low self-esteem and used to dread getting lost. It was terrifying. Now I'm able to live life to the full.
"I'm lucky that I've found an Alzheimer's drug that works for me. However, these drugs don't work for everyone so we must continue the search for more and better options."
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The drugs or classes of drugs identified as potential treatments are:
:: High blood pressure medications including Nilvadipine, from the calcium channel blockers family.
:: Diabetes medications exenatide and liraglutide, which have been shown to stimulate the brain.
:: Minocycline, an antibiotic used to treat acne.
:: Acitretin, a drug used to treat psoriasis which researchers found modifies the way proteins linked to dementia form.
The report will be published in the Nature Reviews Drug Discovery journal.