Rimadyl may be one of the most popular prescription drugs ever for dogs.

If you have a dog, there is a chance your pet could be taking it some day. But some dog owners claim the side effects of Rimadyl can be deadly.

Jezebel is a happy, healthy dog today. But Janice Nollar says her black lab was nearly killed by the very medicine meant to keep her alive.

"She trusted us and we thought we were doing the right thing for her," Nollar said.

Nollar said the culprit for her dog's health problems was Rimadyl.

Millions of dogs with arthritis and other painful conditions take the drug with excellent results. But a small percentage of dog owners say the effects can be devastating.

"She was vomiting, really lethargic, wouldn't get out of bed, wouldn't eat anything," Nollar said.

Nollar suspected a bad drug reaction.

"I was just surfing the Internet. I found the side effects and I was floored," Nollar said.

Jezebel lingered near death for eight days.

"I gave the veterinarian side effects and he looked into it and called Pfizer and came to the conclusion that the medication probably was causing her liver to stop functioning," Nollar said.

Nollar is one of hundreds of pet owners who joined a class action suit claiming Rimadyl killed or harmed their pets.

The case settled out of court last year. But the company does not admit Rimadyl as the cause of illness or death.

Questions about Rimadyl were being raised at least a year before the civil suit was filed in 1999.

The Food and Drug Administration says the drug was behind 39 percent of all adverse drug reactions reported for dogs in 1998.

More than 3,600 cases were reported, and according to the FDA, 13 percent involved the death of the dog.

There is no doubt that the drug will continue to be prescribed. There is also no doubt that it will continue to help certain animals and that certain animals will continue to die from taking it.

Pfizer has said it is doing "everything possible to educate consumers"

Proponents, like veterinary surgeon Alan Schulman, say Rimadyl is keeping many dogs alive and is well worth the risk.

"The benefits, if used intelligently, really far outweigh the potential disadvantages if the animals are monitored and diagnosed appropriately," Schulman said.

But those who say they have experienced the other side of Rimadyl remain unconvinced.

"They keep seeing this in dogs and yet it's still out there for sale. Personally, I think it should be pulled," Nollar said.

Pfizer said that dogs should be tested for pre-existing liver conditions before taking Rimadyl and they should be taken off the drug immediately if side effects such as vomiting or loss of appetite occur. If you suspect your dog is having a bad reaction, call your veterinarian.