Literally EVERY substance known to man is "lethal" if given in a high enough dose over a short enough time frame - even water (see article on Water intoxication: https://www.medicaldaily.com/water-intoxication-just-how-much-h2o-does-it-take-kill-person-312958). The LD50 (lethal dose to 50% of the population if everyone took that amount) for IVM is approximately 45 mg/kg. Each tube of 1.87% IVM "horse" paste has 113.7 mg of IVM if you took the hole tube in one dose. Simple math, LD50 of "horse" for a 200-pound human would equate to 9000 mg or just over 79 tubes (taken all at once, BTW) - so yes, one could technically die from taking too much horse paste but they would have to be trying REALLY hard to do it unless they are allergic to it.