ivermectin

Ivermectin

(Ivomec, Heartgard 30, Acarexx, Iverheart Plus)

THE PET PHARMACY
By Wendy C. Brooks, DVM, DipABVP
Educational Director, VeterinaryPartner.com

Ivermectin

(Ivomec, Heartgard 30, Acarexx, Iverheart Plus)

Brand names: Ivomec, Iverhart Plus, Heartgard30 and Acarexx

Available in tablets/chewables for heartworm prevention, topical solution for ear mite treatment, or as oral or injectable solution for other parasite problems

How This Medication is Used
In the mid-1980s, ivermectin was introduced as probably the most broad-spectrum anti-parasite medication ever. It is effective against most common intestinal worms (except tapeworms), most mites, and some lice. It is not effective against fleas, ticks, flies, or flukes. It is effective against larval heartworms (the microfilariae that circulate in the blood) but not against adult heartworms that live in the heart and pulmonary arteries.

The most common uses in small animal practice for ivermectin would include:
Monthly prevention of heartworm infection
Treatment of ear mite situations
Clearing heartworm larvae in active heartworm infection
Treatment of sarcoptic, notoedric or demodectic mange
It should be noted that doses of ivermectin used for prevention and treatment of heartworm disease are approximately 50 times lower than doses used for other parasites.

Side Effects
Side effects are not a concern with the extremely low doses used in commercially marketed heartworm preventives. Problems may arise when higher doses, such as those used against mites, are employed.

Side effects generally do not occur with any anti-mange doses of ivermectin except in Collies, Shetland sheepdogs, Australian shepherds, and Old English sheepdogs, though some individual animals that are not members of these sensitive breeds may also be prone to side effects. Very low-test doses are often recommended to identify these individuals regardless of their breed. Collies with ivermectin sensitivity have been found to have a mutant gene for what is called the "P-glycoprotein." The P-glycoprotein has been studied largely because overexpression of this protein (i.e., having more of it than normal) results poor function of chemotherapy drugs in the treatment of cancer. The P-glycoprotein appears to be involved in keeping drugs out of certain body tissues. Having excess P-glycoprotein keeps chemotherapy drugs from reaching the tumor; having a mutant/non-functional protein fails to keep medications like ivermectin out of the central nervous system. Approximately 35% of Collies appear affected by this condition. There is now a test for P-glycoprotein mutation so that ivermectin sensitive dogs can be identified. This is a DNA test using an oral swab. Test kits can be ordered directly from the Washington State University Veterinary School via www.vetmed.wsu.edu/depts-vcpl.

Heartworm preventive doses are so low that side effects are not produced even in ivermectin sensitive individuals.

Side effects of concern are: dilated pupils and drunken gait that can progress to respiratory paralysis and death if medication is not withdrawn and supportive care is withheld.

Interactions with Other Drugs
Ivermectin should not be used in combination with Valiumor related tranquilizers. It should not be used in conjunction with amitraz (Mitaban©) dips nor with amitraz tick prevention collars (Preventic© collars). These medications are all members of the monoamine oxidase inhibitor group and when they are used together their effects add together creating sedation and adverse neurologic effects.

Concerns and Cautions
Ivermectin use in pregnancy and lactation is not felt to be a problem.

Ivermectin has an extremely bitter taste and is best disguised in food if it is to be used orally long term (as in the treatment of demodectic mange).

Use of oral/injectable ivermectin in small animals for anything other than heartworm prevention is considered off-label use and is not approved by the FDA.

Again, the breeds considered at high risk for ivermectin toxicity are collies, Shetland sheepdogs, Australian shepherds, and Old English sheepdogs. Not every individual dog from these breeds is sensitive to ivermectin. It is possible to test an individual using a low dose of ivermectin.

Topical ivermectin
for ears (Acarexx®) is FDA approved for cats and kittens over 4 weeks of age.

While we recognize that it is possible to buy ivermectin (Ivomec®) through some catalogs, we strongly discourage this practice given the precise doses used for small animals and the potential for serious side effects if the product is incorrectly used.

Copyright 2007 - 2008 by the Veterinary Information Network, Inc. All rights reserved.
This work was originally published by Veterinary Information Network, Inc. (VIN)
and is republished with VIN's permission.

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The above information is simply informational. It's intent is not to replace the advice of a veterinarian nor to assist you in making a diagnosis of your pet. Please consult with your own veterinarian for confirmation of any diagnosis. Your pets life may depend on it.