Experts say we need more options for treating ADHD, and a 2025 study suggests one option might already be stocked at the chemist.
Around a quarter of patients with ADHD (attention-deficit/hyperactivity disorder) find that existing medications for the condition do not improve their symptoms.
And for others, the benefits of the stimulants commonly prescribed for ADHD are outweighed by the side effects: raised blood pressure, loss of appetite, headaches, trouble sleeping, and the risk of misuse.
In a search for alternative treatments, a team of researchers from institutions across Europe has found a common blood pressure medication could be a good candidate: amlodipine, often sold under the brand name Norvasc.
In an initial experiment, seven groups of spontaneously hypertensive rats (which are sometimes used as a model of ADHD) were each given a regimen of a different treatment and then faced with a regular test designed to assess their movement and level of spontaneity.
The only drug that had a significant effect on rat behavior was amlodipine, administered daily for 30 days.
Having identified this potential candidate, the researchers proceeded to test on zebrafish, which were genetically modified to be more hyperactive and impulsive, behaviors we associate with ADHD in humans.
When these fish were given amlodipine, however, their hyperactive traits effectively disappeared.
In another set of experiments, researchers gave fish methylphenidate (better known by its brand name Ritalin) to see how it compared to amlodipine in terms of curbing impulsivity.
Both medications had similarly significant effects when it came to reining in impulsive behaviors.
While these animal studies suggest amlodipine could be worth researching further, we still don't know if it would actually be effective for treating ADHD in humans.
Just because it seems to have some relevant effects on rats and genetically modified zebrafish doesn't mean it will work the same in humans with real ADHD. But these animal studies provide evidence for scientists to proceed to human clinical trials.
The researchers did analyze existing UK Biobank data from people who happened to be taking amlodipine for hypertension, using genetic scores to estimate each person's ADHD risk.
While this part of the study is observational (and therefore cannot show cause and effect), it reveals that people taking amlodipine were less likely to report mood swings or risk-taking, two traits linked to ADHD: another hint that this could be worth researching further.
The good thing with amlodipine is that it's already approved for treating high blood pressure.
In the US, more than 70 million people are taking this drug regularly, which means scientists are well aware of the risks and benefits.
While it's generally considered safe, amlodipine comes with its own set of side effects: it can lead to fatigue, nausea, and gum irritation, to name a few.
"Repurposing amlodipine, a well-established blood pressure medication, offers a promising and swift pathway to address ADHD symptoms," says neuroscientist Matthew Parker of the University of Surrey in the UK.
"Our research indicates that, due to its existing approval and safety profile, amlodipine could be rapidly redeployed as a treatment option for ADHD, potentially providing relief to patients sooner than developing new medications."
The research has been published in Neuropsychopharmacology.
This article was fact-checked by Carly Cassella and edited by Carly Cassella. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.