What Is the Best Pet Heartworm Medicine?

With many pet heartworm medications on the market, it's hard to know which medicine is best. The medications range in prices, offer different dosing instructions and even have differing side effects. Learn how to decide the medication that will fit your lifestyle and your dog or cat's needs.

How to Choose Pet Heartworm Medications

Usually, pet owners decide which medication is right for their pet by deciding which method works best. Pet heartworm medications come in three styles: chewables, pills or topical ointments.

There are benefits to each method, but also some drawbacks. For example, chewables taste good to a cat or dog making them easy to give. If a dog or cat reaches the chewables, they might tear into the packaging in your absence and overdose on the medication.

Pills are harder to give, but it's unlikely your pet will be tempted to rip into the package if they get hold of it. You also must remember to give those chewables or pills on a regular basis. Skipping a pill or chewable for even a few days increases the risk of heartworm infections.

Topical medications require you to squeeze drops between your animal's shoulder blades. If you have multiple pets, it's important to keep the animals from licking each other for at least a few hours to prevent accidental ingestion of the medication. Also, some animals develop skin rashes after receiving their topical pet heartworm medication.

List of Common Pet Heartworm Medications

Common heartworm medications include:

  • Ivermectin
  • Merial
  • Pyrantel
  • Selamectin

Pros and Cons of Ivermectin

Ivermectin is used to treat parasitic worms, including heartworms, but also help kill some varieties of mites and lice. The medication is usually used on dogs, though it is best avoided on collies because of a genetic disorder that causes this breed to be sensitive to Ivermectin.

Brands that use Ivermectin include:

  • Iverhart Plus (by VirbacVet)
  • Ivomec (by Merial)
  • Heartgard (by Merial)
  • Tri-Heart Plus (by Intervet)

There are few side effects because Ivermectin is effective at killing parasites with low doses. The only risk of side effects occurs if your pet overdoses. In that case, watch for pupil dilation and staggering while walking.

Pros and Cons of Pyrantel

Pyrantel works by paralyzing the parasitic worms within a host's body. The worms die off and are then passed through the intestines. Repetitive doses are necessary to killing off all parasitic worms within the animal's body. Products containing Pyrantel include:

  • Iverhart Plus (by VirbacVet)
  • Nemex (by Pfizer)
  • RFD Liquid Wormer (by Pfizer)
  • Strongid T (by Pfizer)

Side effects include diarrhea, straining during a bowel movement and vomiting, though most animals never show any signs of a side effects. Straining only occurs when worm bodies collect in the bowels creating larger masses of excrement.

Pros and Cons of Selamectin

Selamectin is found in Pfizer's Revolution medications. The medication kills parasitic worms, fleas, ticks, mange and heartworm. The medication works by impairing the parasites nervous system. It's one of the most commonly used heartworm medications for cats.

Side effects of Selamectin include diarrhea, excessive drooling, lethargy, loss of appetite, muscle spasms and vomiting.