The antidote is magnesium, forreal. Glycinate is best as it's non-laxative and glycine itself is very relaxing. Helps potentiate effects for some/reduce tolerance as well. Potentiation never happened for me, I suppose a bit more sedation just from the glycine. Magnesium L-theronate is also good, not sedating, more of a nootropic type, but these are both the most bioavailable forms of it. Citrate is also good and relaxing I've found, especially on the muscles, but it can make you shit which honestly a lot of opioid users would benefit from. Opioids deplete your body of magnesium on top of that so everyone who uses opioids, kratom, oxy, whatever, should take citrate or something, IMO. Probably 70% of Americans are magnesium deficient to an extent and have no idea.
The ones that do find out, like myself years back, find that it can cause extreme psychosis. I remember getting magnesium citrate "calm" gummies because I heard it can reduce tolerance, and like, 30 minutes later, I felt the most normal I'd felt in months, I could not fucking believe it. Apparently THC can deplete magnesium as well. I don't know if this has been scientifically proven, but a lot of cannabis users reached a point where they felt paranoid a lot high or not. Some who'd get paranoid just high would take magnesium an hour or so before they smoked and they'd have a good high. This is something that actually a ton of people have anecdotally reported, so I think there's some truth that maybe excess THC can speed up an already low level of magnesium. Perhaps it's smoke in particular, or the anxiolytic effect of the magnesium was directly responsible.
But yea, seriously, magnesium. I haven't felt any type of agitation from kratom ever since I started using it. I use L-theronate usually during the day, glycinate at night since it's sedating and great for sleep and muscle relaxation. Although, the calm citrate gummies relax my muscles even more, which they shouldn't... Only the gummies too. I've gotten the calm brand in powder form and it didn't offer the same result.