ProHeart 6 Heartworm Preventive Recall

FDA: Side effects seen after ProHeart 6 given; company defends drug

09:37 PM CDT on Friday, September 3, 2004

By ALINE McKENZIE / The Dallas Morning News

A twice-a-year heartworm preventive drug for dogs has been recalled by the Food and Drug Administration after reports of more than 5,000 "adverse effects," including about 500 deaths.

The FDA ordered Friday that veterinarians not give the time-released ProHeart 6 to any more dogs, and that its maker, Fort Dodge Animal Health, stop producing the drug. It has been administered to horses and cattle with no reported problems.

In some cases, it's not clear whether the deaths were directly caused by the drug, but in other cases, the link was strong, said Dr. Stephen F. Sundlof, director of the FDA's Center for Veterinary Medicine.

"We felt it was important to not expose any more dogs to this product," he said.

"We don't really understand why this product is causing these problems," he said. "The company has looked into this and is unable to ... find a reason why these adverse effects are occurring."

The drug, also known as moxidectin, went on the market in 2001. In clinical trials that used higher doses than vets give, few symptoms were seen, Dr. Sundlof said.

But by Aug. 4, 5,552 adverse effects – including bleeding, vomiting, lethargy and seizures – had been reported to the FDA.

Dr. Rami Cobb, vice president of research and development for Fort Dodge, said the number of reports pales next to the more than 18 million doses that have been given in three years.

"We report any time anyone telephones us, even with a question," she said. "This is really a very safe and a very effective drug."

Dr. Bob Hawthorne of White Rock Animal Hospital in Dallas said he gives ProHeart 6 to about 200 to 300 dogs in his practice, although he monitors their liver and kidney functions.

"I haven't had any problems with it, although I haven't used it as a wholesale treatment," he said. He said he is cautious with any new medication on the market.

Dr. Trisha Ballard of the Alternative Veterinary Hospital in Carrollton said she doesn't use ProHeart 6 for several reasons.

"I don't believe in reinventing the wheel," she said. "We have many heartworm medications that have been available for years that are highly effective."

In addition, with ProHeart 6, the dog must be brought into the office, which can be stressful. Plus, there are fees for the office visit, the drug, the injection and disposal of the syringe, she said.

"That's harder on the dog than just giving it a treat at home," she said.