Old Drugs, New Hope? The Search for Repurposed Treatments for Parkinson's and Alzheimer's
If someone you love has Parkinson's or Alzheimer's, you know how it feels to watch a person slowly change while medicine seems to offer so little. It's no wonder that stories of old, cheap drugs bringing people back spread so quickly. Some of these ideas are being tested in serious research, and some are still only hopeful stories. Here's an honest look at where things stand.
Developing a brand-new medicine typically takes 10 to 15 years and can cost billions, and Parkinson's and Alzheimer's have been especially hard to crack. So researchers are increasingly asking a simple question: could a medicine that already exists for something else help?
Repurposed drugs have big advantages. Their safety is already well understood, they're often cheap, and they can move into trials much faster. As we explored in our article on patients who were right before science caught up, some of medicine's biggest breakthroughs began exactly this way.
Diabetes Drugs: The Biggest Hope So Far
The most closely watched candidates are GLP-1 drugs, the family of diabetes and weight-loss medicines that includes semaglutide (Ozempic and Wegovy). Scientists noticed that GLP-1 receptors in the brain are involved in learning and protecting nerve cells, and that these drugs reduce inflammation, which may play a role in neurodegenerative disease.
The early signs were encouraging. An analysis of dementia diagnoses recorded during three large heart trials found that people with type 2 diabetes who took semaglutide or liraglutide were about half as likely to be diagnosed with dementia as those on placebo.
In Parkinson's, the results have been mixed. A 2024 study in the New England Journal of Medicine found that people with early Parkinson's taking lixisenatide had slightly less worsening of movement symptoms over a year than those on placebo, though many had nausea. But a Lancet study found that nearly two years of weekly exenatide injections didn't slow the disease. (The journal has since flagged concerns about how the trial was run at one site, and an investigation is under way.)
Alzheimer's brought a bigger disappointment. Two large phase 3 trials of semaglutide in people with early Alzheimer's didn't show improvements. Some scientists think they know why: semaglutide doesn't cross easily from the blood into the brain. Researchers are now designing and testing versions intended to reach the brain more easily, so this story isn't over.
The semaglutide trials for Alzheimer's didn't work, but they taught scientists that a drug needs to reach the brain properly to help. That lesson is already shaping the next generation of treatments.
Other Candidates Worth Watching
One of the most interesting ideas involves ambroxol, a cough medicine widely used in Europe. The most frequent genetic risk factor for Parkinson's is a change in a gene called GBA, which affects an enzyme that helps cells clear out waste. Lab studies suggest ambroxol can boost that enzyme's activity, so researchers are now running controlled trials, including some focused on people with Parkinson's who carry the gene change.
It's slow, careful work, and that's the point. Each trial tells us something, even when the answer is no.
Patient Reports, Online Claims and the Evidence Gap
If you follow health news online, you may have come across William Makis, a former Alberta doctor who has not held a medical licence since 2019 and has been widely followed online for promoting ivermectin, particularly for cancer. In recent years he has also shared reports of patients with Parkinson's and Alzheimer's. Alberta courts have since ordered him to stop offering health advice, including cancer "coaching", in rulings about practising without a licence rather than about ivermectin itself.
These reports are genuinely moving. Makis has shared accounts of people with Parkinson's regaining movement, including an older man whose family said his shuffling and tremors improved dramatically after several months on a protocol of ivermectin and fenbendazole. For dementia, families have described loved ones seeming calmer, sleeping better or remembering more. It's easy to understand why these stories spread, and why families facing these diseases would want to believe them.
There's also a scientific idea behind them. Supporters point to lab research suggesting ivermectin affects P2X4, a receptor on brain cells that may be involved in inflammation in several neurological conditions. It's an interesting hypothesis, and it deserves proper study.
But it's important to be clear about where the evidence stands today. To our knowledge, no clinical trials have yet tested ivermectin in people with Parkinson's or Alzheimer's. The research so far is in cells and animals, and the patient reports are individual stories rather than controlled studies. That matters, because Parkinson's symptoms naturally fluctuate from day to day and can change with adjustments to regular medication, and families may notice good days more when they're hoping for them. Stories like these are how many discoveries begin, but they can't tell us on their own whether a treatment works.
This is why we need to push for more testing in this area. Perhaps the most important point is this. Alzheimer's now has its first treatments that can modestly slow the disease for some people in the early stages, though access varies by country and they aren't suitable for everyone. If ivermectin does help people with these diseases, a well-designed trial is the way to prove it, and it would be wonderful news. Let's get these trials started.
The medicines being studied
- GLP-1 receptor agonists (semaglutide, lixisenatide, exenatide, liraglutide) These prescription medicines copy a natural hormone that helps control blood sugar and appetite. GLP-1 receptors are also found in the brain, where they may help protect nerve cells and reduce inflammation. They're being studied in Parkinson's and Alzheimer's, with mixed results so far. They're prescription-only and not recommended for these conditions outside clinical trials.
- Ambroxol Ambroxol is a cough medicine that helps loosen mucus. Lab research suggests it can boost an enzyme linked to the most common genetic risk factor for Parkinson's. It's currently being tested in clinical trials at doses far above those used for coughs, which should only be taken under medical supervision.
- Ivermectin Ivermectin is an anti-parasitic medicine, approved in various countries for parasitic infections such as river blindness, threadworm (strongyloidiasis) and scabies. Lab research suggests it may affect a brain receptor called P2X4. It is not approved for Parkinson's or Alzheimer's, and there are no established clinical results supporting its use for either condition.
The search for better treatments for Parkinson's and Alzheimer's is one of the most hopeful areas in medicine right now, and old drugs are a big part of it. Some ideas will succeed and many won't, but each careful trial brings us closer. If you or someone you love is living with one of these conditions, stay curious, share what you read with your neurologist, and ask about clinical trials you might be able to join. Hope is most powerful when it's paired with good evidence and a care team you trust.
- Meissner, W.G. et al., 2024. Trial of Lixisenatide in Early Parkinson's Disease. New England Journal of Medicine, 390(13), 1176–1185. https://doi.org/10.1056/NEJMoa2312323
- Vijiaratnam, N. et al., 2025. Exenatide once a week versus placebo as a potential disease-modifying treatment for people with Parkinson's disease in the UK: a phase 3, multicentre, double-blind, parallel-group, randomised, placebo-controlled trial. The Lancet, 405(10479), 627–636. https://doi.org/10.1016/S0140-6736(24)02808-3. Expression of Concern: The Lancet, 2026. https://doi.org/10.1016/S0140-6736(26)01241-9
- Cummings, J.L., Atri, A., Sano, M. et al., 2026. Efficacy and safety of oral semaglutide 14 mg (flexible dose) in early-stage symptomatic Alzheimer's disease (evoke and evoke+): two phase 3, randomised, placebo-controlled trials. The Lancet, 407(10544), 2167–2179. https://doi.org/10.1016/S0140-6736(26)00459-9
- Nørgaard, C.H. et al., 2022. Treatment with glucagon-like peptide-1 receptor agonists and incidence of dementia: data from pooled double-blind randomized controlled trials and nationwide disease and prescription registers. Alzheimer's & Dementia (N Y), 8(1), e12268. https://doi.org/10.1002/trc2.12268
- GREAT trial investigators, 2024. Study protocol of the GRoningen early-PD Ambroxol treatment (GREAT) trial: a randomized, double-blind, placebo-controlled, single center trial with ambroxol in Parkinson patients with a GBA mutation. BMC Neurology, 24. https://doi.org/10.1186/s12883-024-03629-9
- College of Physicians and Surgeons of Alberta v Makis, 2026 ABKB 159 (4 March 2026); leave to appeal denied, 2026 ABCA 198 (17 June 2026).
This article is intended for informational and educational purposes only and is not medical advice. It discusses emerging research and does not recommend any medicine for Parkinson's disease or Alzheimer's disease. The medicines described here should only be used as prescribed or within a clinical trial. Descriptions of trials reflect the published sources cited above at the time of writing. Always speak to your own neurologist or care team before making any change to treatment.