Skip to content

Healthy Dogs

Select An Article
Font Size

Heartworm Prevention and Medicine for Dogs



Heartgard Plus is a popular chewable tablet that combines ivermectin with pyrantel pamoate. This combination prevents heartworms and also controls roundworms and hookworms.

Interceptor (milbemycin oxime) is another orally administered once-a-month heartworm preventive that also acts on the L4 larvae. Like Heartgard, this drug is marketed in different dosages based on the weight of the dog. Interceptor also controls hookworms, roundworms, and whipworms. This drug is safer to use on Collies and Collie crosses.

Selamectin (Revolution) isa once-a-month liquid heartworm preventive applied to the skin of the dog’s neck between the shoulder blades. It is available from your veterinarian in premeasured doses based on the dog’s size and age. A principal advantage of selamectin is that it also controls adult fleas and prevents flea eggs from hatching for one month. In addition, it treats ear mites and the mites that cause scabies.

Ivermectin Sensitivity

Some breeds show an increased susceptibility to the potential toxicity of ivermectin and similar drugs. In these dogs, there is a defect of the gene MDR-1. This is a multi-drug transporter gene that influences the movement of drugs across the blood brain barrier. Dogs who are homozygous for this autosomal recessive trait will have severe, potentially fatal reactions to some drugs, including ivermectin. Dogs who are heterozygous may be able to safely take the medications, but may pass on the defective trait to their offspring.

A genetic test for this defect is available through Washington State University’s Veterinary Laboratory of Clinical Pharmacology. A cheek swab can be sent to determine if your dog has the gene. This testing is recommended for Collies, Border Collies, Shetland Sheepdogs, Australian Shepherds, Old English Sheepdogs, and longhaired Whippets. In breeds such as the Collie, more than 70 percent of the dogs tested are either homozygous for this defect or carry it.

WebMD Veterinary Reference from "Dog Owner's Home Veterinary Handbook"

Next Article:

Today on WebMD

bulldog in party hat
Breeds with longevity
Doberman Pinscher Clipped Ears
The facts about ear cropping and tail docking.
dog with duck in mouth
Which are considered smartest?
boxer dog
What are their health issues?
Pit bull looking up
Pets: Is My Dog Normal
Dog scratching behind ear
dog catching frisbee

Love your pets, hate your allergies?

Get tips for relief.

Loading ...

Sending your email...

This feature is temporarily unavailable. Please try again later.


Now check your email account on your mobile phone to download your new app.

Dog Breed RMQ
Lady owner feeding dog
bulldog in party hat