An international panel of experts reviewed 80 existing drugs and identified the three most promising candidates for the treatment of Alzheimer's disease: the shingles vaccine Zostavax, sildenafil (Viagra), and riluzole.[1][2] The shingles vaccine is based on a weakened strain of the virus, and epidemiological data from Australia, Wales and Canada suggest that it reduces the risk of dementia by up to 20 percent.[1] Sildenafil helps protect nerve cells and reduces the build-up of tau protein in the brain, while in tests on mice it improved cognitive function due to increased blood flow to the brain.[2] Riluzole, which is used to treat amyotrophic lateral sclerosis, has shown promising results in improving cognitive function and reducing tau levels in animal studies.[2] All three drugs were selected because they target relevant mechanisms of Alzheimer's disease, have shown promise in cell and animal models, and are safe for use in the elderly.[2] Experts recommend that these drugs be tested in clinical trials to understand their benefits for people with Alzheimer's disease or at risk.[2]