The U.S. approved the first prescription drug to curb the appetite of overweight dogs, a growing health problem.

The Food and Drug Administration has cleared Pfizer Inc. to market a drug called Slentrol for use in the estimated 5 percent of U.S. dogs that are obese and the additional 20 percent to 30 percent that are overweight.

The population of dogs with a weight problem has grown as owners stuff their pets with table scraps and treats in addition to dog food, said George C. Fahey Jr., a professor of animal sciences at the University of Illinois at Urbana-Champaign who specializes in pet nutrition.

"It would be helpful," Fahey said of Slentrol in a telephone interview. "It would be more helpful if people could feed their dogs less. That would be turning off the spigot instead of mopping the floor. Not everybody's going to do that."

Dogs that are 20 percent more than their ideal weight are considered obese. As with humans, the condition can lead to diabetes along with heart and joint problems. There are about 61.5 million pet dogs in the U.S., according to the American Veterinary Medical Association, based in Schaumburg, Illinois.

The FDA warned Slentrol can cause dogs to vomit and experience loose stools, diarrhea, lethargy and loss of appetite.

The medication will include a warning saying the drug isn't to be used by humans.

BLOCKS FAT ABSORPTION

The drug reduces appetite and fat absorption to produce weight loss, according to the FDA. It blocks the assembly and release of lipoproteins into the bloodstream.

Dog owners can give the liquid medicine directly or by adding it to food. It is to be given in varying amounts, with an initial dose for 14 days. A veterinarian will determine the dog's progress on a monthly basis and adjust the dose depending on weight loss, the FDA said.

After a dog reaches the desired weight, Pfizer suggests continued use for three months while the best level of food and exercise are determined, the FDA said.