I feel like on the principle of harm reduction we should just let these people try it, in the correct, safe, form/dose with medical supervision.
As an aside, ivermectin is a GlyR agonist, so it seems at least scientifically plausible it could do something for some people with autism. But I'm not a doctor, just an autist with a special interest in psychopharmacology.
I don’t think the principle of harm reduction can justify this kind of active child abuse.
While veterinary formulations are not meant for human consumption they are meant for internal consumption [1] by the intended species and dosage is actually easy and accurate, at least when the standard anti-helminthic dosage of 200 µg/kg is used since in that case the dosage can simply be set on the syringe just like it would be done with a horse. The difference between the human and veterinary formulations of Ivermectin is in the used base, a paste for the veterinary version versus a solid filler-diluent for the human preparation. The active ingredient is identical and sourced from the same Indian manufacturers like is the case for so many other off-patent medications.
[1] there is some off-label external use of Ivermectin paste for dermal conditions, the efficacy of which has not been proven
At worst, you'll quench your thirst, but at best, you may get rid of that pesky tumor!
The only proactive solution is deterrence, which starts with dealing with the idiots doing it in public.
So, yes, there are veterinary preparations humans should not use just like there are many more human preparations which should never be given to animals. Dosage can also differ between species. Many veterinary preparations are abused as narcotics, e.g. Ketamine and Xylazine. With all that said and with the required knowledge available there are many veterinary preparations which can be used by humans since they are either identical - e.g. Prascend (used to treat Cushing's disease in horses) is more or less identical to Permax (used to treat Parkinson's disease in humans, withdrawn from many markets), both have pergolide as active ingredient. Ivermectin is another example which can be found in many veterinary preparations as well as those for humans, often using a different base but otherwise identical. The extremely polarised debate around SARS2 and the use of Ivermectin have led to a proliferation of dire warnings about the differences between veterinary and human preparations so it is advisable to look for older texts when searching for information about these differences.
If I were to need medication and were offered the choice between a preparation made for human use and one for veterinary use I would choose the first one. If the choice were between a veterinary preparation and no medication and if I deemed the need to be sufficiently high I would take the veterinary preparation after having read up on the ingredients. If I were to need Ivermectin and were offered the choice to either get a box of 10 pills for €250 or a (new) syringe of Noromectin ('horse paste') for €5 (which is what these cost, thereabouts) I would take the horse paste without any qualms.