The Food and Drug Administration has approved the first obesity drug to treat America's increasingly overweight dogs.

The drug, called Slentrol, is manufactured by Pfizer Inc. and is supposed to decrease the animal's appetite and fat absorption. Also known as dirlotapide, the drug can has some serious side effects, including vomiting, loose stools, diarrhea and lethargy.

"This is a welcome addition to animal therapies because dog obesity appears to be increasing," said Stephen Sundlof, head of FDA's Center for Veterinary Medicine.

Overweight dogs are at risk for developing diabetes, heart trouble, joint problems and other complications just like their masters, according to the FDA.

Slentrol is not designed for human use and will carry warnings to discourage people from using it, the FDA said.

The drug will only be available through veterinarians and will come in various doses. Pfizer recommends use of Slentrol for three months, according to the agency.

In the U.S. about 40 percent of all dogs or about 17 million animals are considered to be overweight or obese according to 2002 data from the American Veterinary Medical Association.

"Why are 40 percent of dogs in the U.S. overweight or obese? The answer is simple: Too much food and too little exercise," said Claudia A. Kirk, DVM, PhD, Associate Professor of Medicine and Nutrition, College of Veterinary Medicine, University of Tennessee.

"In today's hectic world, it's a challenge for many dog owners to find time to ensure their pets get adequate exercise. And in our culture, we often equate food with love - without being aware of potential adverse health consequences. For both pet owners and veterinarians trying to manage a dog's weight, these habits can be a source of genuine frustration."

Slentrol gives veterinarians an additional tool when diet modification and increased exercise are difficult to implement successfully.

The drug decreases a dog's appetite thereby reducing food intake, making it easier for owners to develop healthier feeding behaviors and attitudes. Slentrol is given once daily as an oral solution, either directly into the mouth or with a small amount of food.

The duration of treatment depends on the amount of weight to be lost.