level of consciousness, confusion, blurred vision, visual hallucinations, loss of coordination and balance, seizures, coma, and death. The CDC advises against consuming doses intended for livestock or doses intended for external use and warns that increasing misuse of ivermectin-containing products is resulting in an increase in harmful overdoses. Veterinary use Ivermectin is routinely used to control parasitic worms in the gastrointestinal tract of ruminant animals. These parasites normally enter the animal when it is grazing, pass the bowel, and set and mature in the intestines, after which they produce eggs that leave the animal via its droppings and can infest new pastures. Ivermectin is only effective in killing some of these parasites, this is because of an increase in anthelmintic resistance. This resistance has arisen from the persistent use of the same anthelmintic drugs for the past 40 years. In dogs, ivermectin is routinely used as prophylaxis against heartworm. Dogs with defects in the P-glycoprotein gene (MDR1), often collie-like herding dogs, can be severely poisoned by ivermectin. The mnemonic "white feet, don't treat" refers to Scotch collies that are vulnerable to ivermectin. Some other dog breeds (especially the Rough Collie, the Smooth Collie, the Shetland Sheepdog, and the Australian Shepherd), also have a high incidence of mutation within the MDR1 gene (coding for P-glycoprotein) and are sensitive to the toxic effects of ivermectin. Clinical evidence suggests kittens are susceptible to ivermectin toxicity. A 0.01% ivermectin topical preparation for treating ear mites in cats is available. Ivermectin is sometimes used as an acaricide in reptiles, both by injection and as a diluted spray. While this works well in some cases, care must be taken, as several species of reptiles are very sensitive to ivermectin. Use in turtles is particularly contraindicated. A characteristic of the antinematodal action of ivermectin is its potency: for instance, to combat Dirofilaria immitis in dogs, ivermectin is effective at 0.001 milligram per kilogram of body weight when administered orally. For dogs, the insecticide spinosad may have the effect of increasing the toxicity of ivermectin. Pharmacology Mechanism of action Ivermectin and its related drugs act by interfering with the nerve and muscle functions of helminths and insects. The drug binds to glutamate-gated chloride channels common to invertebrate nerve and muscle cells. The binding pushes the channels open, which increases the flow of chloride ions and hyper-polarizes the cell membranes, paralyzing and killing the invertebrate. Ivermectin is safe for