Ivermectin

Major Uses

Ivermectin is an antiparasitic that is commonly used in horses to control large strongyles, small strongyles, pinworms, ascarids, hairworms, large-mouth stomach worms, neck threadworms, bots, lungworms, intestinal threadworms, and summer sores. For dogs and cats, ivermectin has proven useful as a microfilaricide, slow-kill adulticide, ectoparasiticide, endoparasiticide, and as a heartworm prevention method.

Common Precautions

Ivermectin should not be used in foals that are younger than 4 months old or puppies less than 6 weeks old. Caution should be used when administering to breeds such as collies, shelties, and Australian shepherds. Lactating and dairy animals should not take ivermectin.

One adverse effect experienced by horses is swelling and pruritus at the ventral mid-line. Dogs using ivermectin as a microfilaricide have been observed experiencing a shock-like reaction, depression, hypothermia, and vomiting. Dogs with the ABCB1 mutation have experienced neurotoxicity. While rare, some horses have also suffered from neurotoxicity while using ivermectin.

Ivermectin should not be used in animals with a known allergy or hypersensitivity to the drug. A veterinarian should be contacted immediately if any unusual symptoms occur or an overdose is suspected. Symptoms associated with an overdose of ivermectin can include vomiting, ataxia, lethargy, hypersalivation, tachycardia, mydriasis, diarrhea, and seizures.

Storage

Ivermectin should be kept at room temperature in a childproof container that is resistant to light. It should be carefully protected from light and stored where children and pets will not be able to reach it. When mixed with water, the solution is stable for up to 72 hours stored at room temperature.

Administration

When using ivermectin to treat susceptible parasites in horses, a typical dose is .2 mg/kg once, or at 4 day intervals if treating lice and mange. When treating dogs for prophylaxis or dirofilariasis, a typical dose is 6-12 micrograms/kg once monthly. When used as an adulticide or pre-adulticide for heartworm in dogs, 10 mg/kg once daily for up to 30 days has shown to be effective. For cats, a typical dose is .024-.4 mg/kg monthly. If a scheduled dose is forgotten, it should be administered as soon as possible. Should it almost be time for the next scheduled dose, the missed dose should be skipped and the regular scheduled dose should be administered. Two doses should never be administered at the same time.

Doses may vary in different species, when the drug is given by a different route or concurrently with other medications, and with regards to a patient's age, breed, and health status. A veterinarian's dosing instructions and/or those printed on the medication label should be followed closely.