Shingles Vaccine, Viagra, and Riluzole Show Promise in Alzheimer’s Disease Research
A growing body of research suggests that existing medications – a shingles vaccine, Viagra (sildenafil), and a motor neurone disease drug called riluzole – could offer new avenues for treating or preventing Alzheimer’s disease. These findings, stemming from studies led by the University of Exeter, represent a potentially faster, safer, and more affordable path toward new treatments than developing drugs from scratch.
The Search for Repurposed Drugs
Alzheimer’s disease remains a significant global health challenge, affecting around one million people in the UK alone, and with one in three individuals born today projected to develop dementia in their lifetime. Despite the urgent need, developing new drugs is a lengthy and expensive process, often taking 10 to 15 years and costing billions of pounds with no guarantee of success. Drug repurposing – identifying new uses for existing medications – offers a compelling alternative.
Key Findings: Three Promising Candidates
An international panel of experts, reviewing 80 existing drugs, identified three as particularly promising candidates for repurposing against Alzheimer’s:
- Zostavax (Shingles Vaccine): Emerging as the front-runner, the shingles vaccine has shown potential in reducing the incidence of dementia. Epidemiological evidence suggests a relative reduction of 16% in incident dementia among vaccinated individuals, according to a systematic review of five studies involving approximately 941,000 people 1. A UK study using primary care data also indicated a 20% relative reduction 4.
- Viagra (Sildenafil): Commonly used to treat erectile dysfunction, Viagra is being investigated for its potential neuroprotective effects.
- Riluzole: A medication used to treat motor neurone disease, riluzole is believed to protect nerve cells by counteracting overactivity in the brain’s signaling system. It may also influence metabolic processes within nerve cells, potentially promoting the formation of new connections 1.
Why These Drugs?
The advantage of repurposing these drugs lies in their established safety profiles. Because they are already approved for other conditions, their side effects are well-documented. Many have lost patent protection, making them more affordable to produce 1.
The Road Ahead: Clinical Trials are Crucial
Despite the encouraging findings, rigorous testing is essential. The next step involves conducting double-blind, controlled clinical studies to compare the effects of these drugs against a placebo. These trials will determine whether the drugs have a genuine effect on Alzheimer’s disease and, if so, how significant that effect is 1. It will likely take considerable time to evaluate their potential as new treatments for this devastating disease.
Recent Developments
Research funded by Alzheimer’s Society and led by the University of Exeter was published in Alzheimer’s Research & Therapy in November 2025 2 and again in February 2026 1, further solidifying the potential of drug repurposing in the fight against Alzheimer’s.