Overland Park, Kan.-The U.S. Food and Drug Administration (FDA) has ordered label changes for ProHeart 6 (moxidectin), a six-month injectable heartworm preventive.
The label changes concern use of the product in heartworm-positive dogs and death, "in rare cases."
In accordance with FDA protocol, manufacturer Fort Dodge Animal Health sent letters to all U.S. practitioners in August outlining the label changes. The company explained that a "low number of heartworm positive dogs experienced coughing or cardiopulmonary signs after receiving ProHeart 6," as well as explaining the second change, "death has been reported in approximately 0.0025 percent of the doses sold in veterinary clinics (approximately 2.5 per 100,000 doses). Some of the reports are associated with severe allergic events, while others appear to be multifactorial in nature. Some are linked to factors not associated with product use." The FDA claims that nine of the 240 reported deaths are directly tied to the drug. The others could not be conclusively connected.
Overall, the company says, year-to-date reported adverse reactions are down 19 percent compared to last year.
By law, drug manufacturers must report all adverse reactions brought to their attention to the FDA.
"When this drug was initially marketed, it was believed to be safe for heartworm positive dogs; then we found that dogs were dying that were heartworm positive," says Dr. Victoria Hampshire, the FDA's adverse drug events coordinator.
She urges practitioners not to view Fort Dodge's letter as "junk mail."
"In the hustle and bustle of everyday practice, it's really important that veterinarians know what kind of dogs they're dealing with," Hampshire says. "The take-home message is to do a thorough physical exam before administering this drug."
In a written statement to DVM Newsmagazine, Fort Dodge stands by the safety and efficacy of its product.
"As is typical in the case of a new product after introduction to a wide population base, we have received reports that were not seen in pre-approval clinical studies." The label change, it says, is all part of FDA's post-approval experience. The product debuted in June 2001.
The statement adds, "We have been in regular correspondence with veterinarians regarding field reports. We have initiated adjustments to the label statements in conjunction with the FDA's Center for Veterinary Medicine, as necessary, to reflect that post-approval experience."
Veterinarians with questions about ProHeart 6 can contact a Fort Dodge technical services veterinarian at (800) 477-1365.
FDA's Annual and Cumulative Adverse Drug Experience Reports lists all adverse drug reports. Visit www.fda.gov/cvm-/index/ade/ade_webrpts.pdf for more information.