Heartworm disease is a serious and potentially fatal condition that can affect dogs and cats. The disease is caused by a parasitic worm transmitted through mosquito bites. Heartworm preventatives are medications designed to prevent this disease by killing the heartworm larvae before they can mature into adult worms.

One thing that may surprise pet owners is that all heartworm preventatives require a prescription from a veterinarian. Many people wonder why this is the case, and there are several good reasons.

• Heartworm preventatives are medications designed to be given to dogs and cats for a certain period, usually monthly. Like all medications, they can have side effects and interactions with other medications. By requiring a prescription, veterinarians can ensure that the medication is safe for your dog or cat and that it will not interact with any other medications they may be taking.
• Heartworm-preventative medications are designed to be effective at specific dosages based on the animal’s weight. Overdosing or underdosing can result in the medication not being effective or causing harm to your dog or cat. By requiring a prescription, veterinarians can ensure the correct dosage is given to each pet.
•  Heartworm preventatives are prescription medications because they are regulated by the FDA. The FDA regulates all medications, including those for pets, to ensure that they are safe and effective. By requiring a prescription, the FDA is able to ensure that heartworm medications are being used in a safe and effective manner.

Why Does my Dog or Cat Need a Heartworm Test?

The American Heartworm Society and most veterinarians recommend an annual heartworm test before prescribing a heartworm preventative. Blood testing ensures that the medication is effective, the pet is not already infected with heartworms, and there are no adverse effects of the medication. Heartworm-preventative medications kill immature heartworm larvae and prevent them from maturing into adults, which causes illness. These medications do not kill adult heartworms.

• A dog or cat that is infected with heartworms will require a different treatment plan. Starting medication without testing can put the pet at risk of serious complications.
• Preventatives are highly effective, but your dog or cat can still become infected with heartworms even while taking the medication. Blood testing detects any new infection and allows for prompt treatment.

If you have any questions or concerns about heartworm prevention for your pet, talk to your veterinarian. They can recommend the best medication for your dog or cat so they receive the best protection from heartworm disease. Learn more about heartworm disease in dogs and cats on our blogs.

This information is not intended to diagnose or treat any disease and is purely educational. Please seek advice from your pet’s veterinarian with any questions regarding your pet’s health.