Tilmicosin is a macrolide antibiotic.

It is used in veterinary medicine for the treatment of bovine respiratory disease and enzootic pneumonia caused by Mannheimia (Pasteurella) haemolytica in sheep.

[3] In humans, Tilmicosin causes fatal cardiotoxic effects at amounts greater than 1 milliliter when injected, something most commonly seen in veterinary personnel and farmers.

[4] Tilmicosin, like most macrolides, is a Calcium channel blocker.

However, because Micotil is formulated for animals like cows, it has exceptionally more potent Ca channel blocking effects in humans with a dose of .5 mL causing significant poisoning and a dose of 5-6 ml being lethal.