Wyeth heartworm drug makes limited return in U.S

By Lisa Richwine

WASHINGTON (Reuters) - Wyeth's Proheart 6 heartworm prevention drug for dogs is returning to the U.S. market with restrictions four years after reports of sometimes deadly reactions led to its recall, U.S. officials said on Thursday.

The U.S. Food and Drug Administration said the company had made manufacturing changes to reduce such complications, but the move still raised questions over why the drug was being sold again.

Wyeth voluntarily recalled the injectable drug in 2004 amid thousands of reports of dogs that had serious and sometimes fatal reactions.

Some dogs given Proheart 6 injections before the recall experienced loss of appetite, lethargy, vomiting, seizures, difficulty walking and jaundice, as well as bleeding disorders, allergies and convulsions, the FDA said.

As many as 485 dog deaths may have been linked to Proheart 6, FDA officials said at a public meeting in 2005. Wyeth officials said on Thursday they could not estimate how many fatalities may have been linked to the drug, saying there could have been other causes.

On Thursday, the company said distribution of Proheart 6 will be limited to veterinarians who register with the manufacturer and complete a Web-based training program. Pet owners will be asked to sign consent forms.

"While we concur with the limited return of ProHeart 6 to the U.S. market, we strongly encourage veterinarians and pet owners to report any possible adverse reactions," Bernadette Dunham, director of the FDA's Center for Veterinary Medicine, said in a statement.

Sen. Charles Grassley, an Iowa Republican who has been critical of the FDA's oversight of drug safety and has been investigating circumstances surrounding Proheart 6, immediately questioned the decision.