I heard of this from the excellent blog by Peter Lloyd Thomas https://www.epiphanyasd.com/2017/08/agmatine-magic-bullet-in-clinical.html
It's derived from the amino acid Arginine and modulates NMDA receptor activity - in other words it can calm down hyperactivity and improve focus (more on that below).
It can be bought here (we got a half kilo since shipping is not cheap): https://www.bulksupplements.com/en-se/search?q=Agmatine%20Sulfate
It arrived with no issue, to us in Europe (shipped direct from their site).
For the sake of what's effectively about the cost of a bottle of supplements, and considering the possible large upside and safety of this, it seems well worth a try.
We tried it (620 mg in 25 kg child - revised dose below!) and got:
More attentive and shows he’s listening more than usual.
Much more calm.
More patient.
More varied babbling:; sounds we’ve not heard before.
Very good eye contact.
When it snowed again he said “More nuhh” (more snow) and then ran to the back of the house and looked out of the window there. He often says “nuhh” when it snows but the “more” is more sophisticated and I don’t recall him running to the other side of the house to see what it’s doing there.
But then... we got really bad sleep, which looks like Ammonia. Which makes sense since it's got Sulphur in it. So we shelved it for a couple of years...
Then Peter published a new article on Agmatine: https://www.epiphanyasd.com/2025/06/agmatine-again-shown-beneficial-in-some.html
So I took the text of the article, and downloaded all the studies (or at least, what's accessable) and dropped them all into ChatGPT, then asked it, what dose might be suitable for a 28 kg child?
It said, 10 mg/kg ; 280 mg, in two 140 mg doses (breakfast and dinner). But ramping up to that across 2-3 weeks, from 5 mg/kg.
That 10 mg/kg applies whatever age, according to what ChatGPT found in the studies.
The effect has been amazing! All the things I listed above, but no Ammonia symptoms.
This is now one of the core supplements we use.
Here's a brief AI summary:
Agmatine sulphate modulates NMDA receptor activity primarily by acting as a non-competitive antagonist. It binds to an allosteric site on the receptor complex (not the glutamate or glycine binding sites), reducing receptor activation without directly blocking the primary ligand sites.
Key roles:
Inhibition of NMDA receptor overactivation: This helps prevent excitotoxicity caused by excessive calcium influx through the receptor.
Neuroprotective effects: By dampening NMDA receptor activity, agmatine can help protect neurons under stress conditions such as ischemia or trauma.
Modulation of synaptic plasticity: Agmatine may influence learning and memory by subtly tuning NMDA-mediated signalling.