I first noticed extreme spookiness/reactivity with 2-3 weeks of starting it. She was always a hot horse but the MSM resulted in nutso reactivity (like, rearing straight/vertically up into the air with all four feet off the ground, Lipizzaner style). Was back to normal a few days after taking her off.
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Add my horse to the list. He’s not a TB but a quarter horse.
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One of mine takes it just fine, he’s typically calm and chill anyway. My other horse absolutely goes nuts on it, spooks at the air. It’s like it makes him paranoid! That was only on one does, too…I knew he may react “hot” to it, so I was ready and watching for signs. I immediately stopped, and he went back to normal right away. Both quarter horses.
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MSM has many known pharmacologic effects. Among them is being a cholinesterase inhibitor. Cholinesterase is an enzyme that rapidly breaks down the neurotransmitter acetylcholine, so that it acetylcholine does not over-stimulate postsynaptic neurons.
So it makes pharmacologic sense to me that MSM may indirectly cause increased neural activity with anxiety as a side-effect when administered for its known anti-inflammatory effects. Couple this with MSM being a drug that penetrates the blood:brain barrier, giving it access to the CNS.
I am not an expert in MSM by any means but I was a fellow in clinical pharmacology at the NIH years ago, and I can appreciate how drug actions, interactions, and side effects might happen. Just sharing my thoughts for those looking for a “how could it do that in my horse?” potential mechanism,.
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It definitely makes some horses spooky. It turned my steady-eddy beginner safe gelding into a snorty spooky borderline dangerous monster. My 4 year old on the other hand has no issues.
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My ottb is randomly mental. I never, ever thought it was MSM in the cosequin I give him. I will definitely be ordering the non MSM type in the future to see if it makes a difference! Thanks CoTH!
