Science1 publisher2 min readPublished
Common blood pressure pill amlodipine eases ADHD-like behaviour in rats and zebrafish
European researchers report that amlodipine, a blood pressure drug taken by over 70 million people in the US, eased ADHD-like traits in animal tests. Its use for the quarter of patients whom existing drugs fail still awaits human trials.
The Scientist · Science desk
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What happened
- Of seven treatment regimens tested on spontaneously hypertensive rats, only amlodipine, given daily for 30 days, significantly changed behaviour on a test of movement and spontaneity.
- Zebrafish genetically modified to be more hyperactive and impulsive saw their hyperactive traits effectively disappear when given amlodipine.
- In a separate fish experiment, amlodipine and methylphenidate (Ritalin) curbed impulsive behaviour to a similar, significant degree.
- In UK Biobank records, people taking amlodipine for hypertension were less likely to report mood swings or risk-taking, two traits linked to ADHD.
Compiled by The ScientistSomething wrong?How this is made
Why it matters
- decision A trial meant to test amlodipine for the quarter of patients whom existing medications do not help would have to enrol those patients specifically, because the fish only showed it matching a stimulant in animals that respond to one.
- cost Patients moving off stimulants would swap raised blood pressure, poor sleep and misuse risk for amlodipine's own side effects, including fatigue, nausea and gum irritation.
- capability Because amlodipine is already approved and widely taken, an ADHD trial would begin with an established safety record. The research team argues this could get it to patients faster than a new drug.
The rat screen in the 2025 paper, published in Neuropsychopharmacology [15], used spontaneously hypertensive rats. The strain is named for its high blood pressure and is sometimes used as a model of ADHD [4]. Amlodipine is a blood pressure drug [11]. It is unclear whether the calmer behaviour has anything to do with ADHD or simply follows from a fall in blood pressure. ScienceAlert's report does not say whether the team checked, name the other six regimens [1], or give doses, sample sizes or effect sizes for any of the experiments.
The zebrafish work answers part of that worry. Those fish were genetically modified to be more hyperactive and impulsive [6], so the result is not tied to one rat strain. The methylphenidate comparison gives the repurposing case less support than it first appears to. Amlodipine matched a stimulant in fish that respond to a stimulant [7]. Repurposing is meant to help the roughly one in four patients whose symptoms do not improve on existing medications [1]. A fish that responds to methylphenidate looks more like the patients those drugs already help. According to ScienceAlert, the animal results give scientists grounds to move to human clinical trials [8].
The human data are observational. The team took UK Biobank records of people already on amlodipine for hypertension and used genetic scores to estimate each person's ADHD risk [9]. People who are prescribed a blood pressure drug can differ from people who are not, and those differences can also shape how they answer questions about mood and risk. The design cannot show cause and effect [9].
In my view the animal data justify a human trial. It should record blood pressure alongside ADHD symptoms, so that the question the rat strain raises gets an answer in people. Matthew Parker, a neuroscientist at the University of Surrey, said: "Repurposing amlodipine, a well-established blood pressure medication, offers a promising and swift pathway to address ADHD symptoms" [13]. He also said: "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" [14].
What to watch
- Registration of a human trial of amlodipine in ADHD, and whether it enrols patients whose symptoms did not improve on existing medications.
- Whether the full Neuropsychopharmacology paper separates the rats' behavioural change from blood pressure lowering and reports effect sizes against methylphenidate.