BRISTOL, Tenn. -

Some dog owners are raising concerns on the internet about a popular medication that kills fleas and heartworms, claiming it may also kill the dog.

Trifexis is a combo pill that tackles two big problems for dog owners. Heartworms and fleas.

However, a growing number of pet parents say the medicine killed their pet. In fact, a local veterinarian says there have been close to 1,000 cases reported to the FDA.

A Change.org petition to have manufacture Eli Lilly pull the drug has more than 3,400 signatures. A Facebook page for the same cause has 5,600.

Dr. Kate Zimmerman, who runs Tri-County Veterinary Hospital told News 5 she believes most dog owners don't have a reason to worry.

"Trifexis is a prescription drug. It should never be used outside a valid patient, client, veterinary relationship, because it is not safe for all dogs. There is no drug in the world that is safe for all dogs, or all people or all anything else," said Zimmerman.

Trifexis is popular with dog owners. The product website claims the drug is the number one selling combination canine parasiticide.

Although Dr.  Zimmerman said she believes there is no direct link between the drug and the deaths of dogs
she is not sold on the product.

"Having an oral product you cant wash off is really, really appealing, but when I started looking at the research, I don't think there is enough of it," said Zimmerman.

However, the Food and Drug Administration, the agency that would do the research, is more concerned with products that may hurt the dog owner.

" The people are always going to trump the dogs.  And we just don't have the funding to do an independent look at pre-existing lab work, pre-existing conditions. You give this drug, and it does what?" said Zimmerman.

The American Veterinary Medical Association says that an independent review of pathology reports on the dogs believed to have died from Ttrifexis found the drug was not the cause of death. The FDA said it is aware of the claims and is closely monitoring those claims.

 Dr Zimmerman says she has some clients who use Trifexis.

" I tell the owners, if it is working and you're happy, go for it, said Zimmerman " The thing that pet owners need to do is keep parasites out of their pets, treat them for heartworm, and keep fleas and ticks off the top."

Dr. Zimmerman told News 5 the best thing to do is talk to your veterinarian and decide how you want to treat your dog. She says there isn't one blanket answer, because no two dogs are the same. She did say that if you use Trifexis, you should also consider using a product to target ticks, because the insect is so prevalent in this region.