USA Today

Like pain relievers for humans, pain relievers for dogs are big business, improving the lives of millions.

And like pain relievers for humans, those for dogs have led to heartache.

Pfizer pioneered the market for dog painkillers when it introduced Rimadyl in 1997. Nearly 15 million dogs have taken it, many for pain from degenerative joint disease, or osteoarthritis.

Rimadyl now has four competitors, with more likely. The market for dog arthritis pain medications tops $130 million a year and is growing about 13 percent a year, consulting firm Wood Mackenzie says.

But 3,200 dogs have died or been put down after taking the drugs, Food and Drug Administration records show. Almost 19,000 dogs have had bad reactions to them.

The FDA says the drugs are safe, if properly used. Drugmakers say fewer than 1 percent of dogs have bad reactions to them. If not for the drugs, many dogs might be put to sleep sooner, they say.

''In theory, the drugs are safer for dogs than aspirin,'' says Steve Marks, head of small-animal medicine at the University of Illinois.

Yet the deaths and other adverse events are a reminder that all drugs pose risks, including those for animals. They also underscore that a drug's risks may not be fully known until the drug is widely sold, despite the FDA's stamp of approval.

Several million dogs received Rimadyl before its warning label was updated to add mention of death in rare cases. No. 2 pain reliever Deramaxx was marketed for a year before its label was so changed.

Despite stronger warnings and other safeguards, the drugs continue to create controversy. Some dog owners and veterinarians say the drugs are being overprescribed by vets who don't always give risk information to owners and who, like doctors for humans, are often educated on drugs by pharmaceutical companies.

''There are no safe drugs. There are only safe doctors,'' says Robert Rogers, founder of the Critter Fixer Pet Hospital in Spring, Texas. ''The large number of adverse events occur with these drugs because veterinarians don't know how to use them.'' Drugmakers share the blame, he says. Their sales representatives often fail to present adequate risk information.are ibuprofen and aspirin for humans. Deramaxx is also a COX-2 inhibitor, like Celebrex and Vioxx, the pain reliever for people withdrawn from the market in September because of heart attack and stroke risk.

NSAIDs cause many of the same problems in dogs that they do in humans: Vomiting, diarrhea and ulcers are the most common. Reports of heart problems associated with dog NSAIDs are rare, the FDA says.

Before getting FDA approval, Rimadyl was tested in 549 dogs; Deramaxx in about 700. That is far fewer than the number of subjects in clinical drug trials for human drugs.