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.

In a letter to FDA Commissioner Andrew von Eschenbach, Grassley asked whether agency safety experts had been involved in the more than 18 meetings and 85 phone calls between the agency and Wyeth's unit to discuss the drug.

Grassley has said his investigation found the FDA scientist who uncovered the link between Proheart 6 use and canine deaths, Victoria Hampshire, was forced from her job at Wyeth's urging. He had requested more information from the agency earlier this year, but said on Thursday the FDA never responded.

Representatives for the FDA had no immediate comment on Grassley's letter.

Company officials said the drug's return would fill a need for longer-term protection from heartworm, which is transmitted by mosquitoes and can kill dogs. Proheart 6 can prevent heartworm for six months. Other heartworm prevention drugs need to be given monthly.

Wyeth said many owners do not keep up with the monthly schedule, putting their dogs at risk.

"We do see a need" for six-month protection, said Rami Cobb, a senior vice president at Fort Dodge Animal Health.

Tests by Fort Dodge Animal Health, the Wyeth unit that makes Proheart 6, found residue from solvents used to make the drug could cause allergic reactions, the FDA said.