Heartworm medicine is essential for protecting your pet from dangerous — and potentially deadly — heartworms. Heartworms are parasitic worms that live in the arteries of the lungs and in the right side of the heart. While heartworm medicine can't eradicate a heartworm infestation, it can help control it and prevent further infestation.

Before starting your pet on any heartworm medicine, it's important to have the pet examined by a veterinarian first. The vet will check for a history of heartworms, examine your pet's overall health and perform a skin test to make sure it's safe to begin the medication.

There are several types of heartworm medicine available, and some can be purchased over the counter. However, if your pet has heartworms, the medication should be obtained from a veterinarian. Prescription heartworm medicine is calculated to kill existing heartworms, and also protect your pet from further infestation.

Many of the prescription medications target the larvae of the heartworms and prevent them from maturing in your pet's body. In some cases, the medication also includes an insecticide to kill the mosquitoes that carry heartworms, preventing them from biting your pet and transmitting the disease.

In addition to medication, monthly testing should be done to monitor your pet's heartworm status. A positive heartworm test is an indication that the heartworm medicine is not working and that your pet may need copious treatments.

If your pet is prescribed heartworm medicine, it is imperative to follow your vet's orders carefully. Giving the medication unknowingly to a pet that is already infected could be harmful. The drugs can be toxic to the larval stages of the heartworms, and your pet could suffer severe side effects.

Finally, adhere to your veterinarian's instructions for administering heartworm medicine. This includes making sure the doses are consistently given on time and are the correct dose. Missing doses of the medication can leave your pet unprotected from the parasites, making regular doses and testing vital for a healthy pet.