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Mebendazole (Telmintic)
Veterinary & Aquatic Services Department, Drs. Foster & Smith
Drug Info
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Mebendazole is an oral medication which must be given 3 consecutive days to treat roundworm, hookworm, whipworm, and tapeworm infections in dogs. Not the dewormer of choice as safer alternatives are available. In addition to treatment, elimination of parasites must also include sanitation and prevention measures to ensure the pet does not become reinfected.

Generic Name

Brand Name

Type of Drug

Form and Storage
Store in a tightly closed container at room temperature.

Indications for Use
Treatment of 1 type of roundworm (ascarid), 2 types of hookworms, whipworms, and 1 type of tapeworm (not effective against the flea tapeworm) in dogs. Not approved for use in cats.

General Information
FDA approved for use in dogs, but NOT cats. Available by prescription. Not the dewormer of choice as safer alternatives are available. Mebendazole has been known to cause liver toxicity in dogs treated with it.

Usual Dose and Administration
Dogs: 9-11 mg/pound in food daily for 3-5 consecutive days depending on the parasite being treated. Mix with a small amount of food which should be eaten before the pet gets the remainder of the meal to ensure the entire amount of medication is ingested. Other safer products are available and preferable. Puppies and kittens need to be tested and dewormed frequently according to a worming schedule, and as advised by your veterinarian.

Side Effects
May see vomiting, diarrhea, or soft stools. Liver failure has been caused by this drug. Signs may include depression, jaundice, bloody diarrhea, lack of appetite, or vomiting.

Do not give this drug to an animal with any form of liver disease.

Do not use in animals hypersensitive (allergic) to it.

Do not use in pregnant or nursing animals.

Some of the parasites can cause human infection. See special note after the fenbendazole section.

Drug or Food Interactions
No drug interactions listed.

Give with food.

May see liver toxicity. Signs may include vomiting, bloody diarrhea, lack of appetite, jaundice, or depression. Contact your veterinarian or the Animal Poison Control Center if you think your pet may have accidentally received or been given an overdose of the medication.

Special Note
Roundworms, hookworms, and tapeworms are zoonotic, meaning they can infect humans. Multiple species carry the roundworm parasite including dogs, cats, raccoons, and pigs. The adult roundworm living in an animal's intestine passes large numbers of eggs in the animal's feces/stool. These eggs contaminate the ground where the animal has defecated. Children who play in the area and do not wash their hands before eating or putting their hands in their mouth, or who eat dirt contaminated with the eggs are most at risk of becoming infected.

The ingested roundworm eggs hatch in the intestine, and the larvae then migrate throughout the body organs including the lungs, liver, eyes, and brain where they can produce the disease known as visceral larval migrans. (Ocular larval migrans if they migrate into the eye.)

The raccoon roundworm is especially harmful as signs progress rapidly and death may precede diagnosis. Clinical signs of infection from raccoon roundworm larvae have been similar to symptoms of rabies in various animal species and humans.

Prevention of roundworm infection in people includes annual stool tests/deworming of pets, child supervision, personal hygiene, washing root-type vegetables, covering sandboxes, gardening with gloves, cleaning up pet stool daily, and not allowing pets to lick hands and face.

Cutaneous larval migrans is caused by hookworm larvae that penetrate the skin of people who come into contact with moist soil harboring the hookworm larvae. In humans, the parasites usually die in the skin leaving a reaction of redness, irritation, and itching. Prevention includes annual stool testing/deworming of pets, wearing shoes outside, and wearing gloves when gardening.

Tapeworms have the capability of causing disease in humans when the proglottid (egg carrying segment of the worm) is passed with the animal's feces. An immature form of the tapeworm develops in a intermediate host (e.g., animal, insect, snail), depending on the type of tapeworm. Tapeworm is always acquired by eating an infected intermediate host such as a flea, dog louse, rabbit, rodent, uncooked or undercooked meats (like beef, lamb, pork, and venison), uncooked or undercooked fish, and dead livestock/wildlife.

Prevention of tapeworms in people would include eliminating any fleas on the pet and in the environment, not allowing the pet to consume rodents and other intermediate hosts, practicing good personal hygiene, preventing fecal contamination of food and water, and not eating uncooked or undercooked meat/fish.

Keep this and all other medications out of the reach of children and pets.

If you think your pet has been poisoned...

Contact your veterinarian or one of the Animal Poison Hotlines (listed below) if you think your pet may have accidentally received or been given an overdose of the medication.

**ASPCA National Animal Poison Control Center

1-888-4ANI-HELP (1-888-426-4435). $65.00 per case, billed to caller's credit card.

Follow-up calls can be made for no additional charge by dialing 888-299-2973.

There is no charge when the call involves a product covered by the Animal Product Safety Service.

**Pet Poison Helpline - 24-hour service available throughout North America for pet owners and veterinary professionals who require assistance with treating a potentially poisoned pet.

1-800-213-6680 ($35.00 per incident). Staffed 24-hours a day.

Click here for a pdf version of this article.  See related products at Pet Supplies  
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