recall its heartworm medication ProHeart®6 from the market until the FDA's concerns about adverse reaction reports associated with the product can be resolved. FDA is requesting that the firm continue to conduct research to determine the cause of related adverse reactions and develop a strategy to help prevent such problems in the future before the product is marketed again. The FDA will convene an independent scientific advisory committee to thoroughly evaluate all available data.

ProHeart®6 is an approved injectable sustained-release heartworm prevention product for dogs. Heartworm disease is a serious and potentially fatal condition of dogs, cats, and other species of mammals. The parasite that causes heartworm disease is transmitted through the bite of a mosquito.

FDA is also advising veterinarians to avoid administering this product to dogs until further notice. Pet owners should consult their veterinarians regarding their pet's health care needs.

Since the product was approved in June 2001, Fort Dodge Animal Health has cooperated with FDA to investigate numerous adverse event reports. As a result, Fort Dodge has voluntarily changed the label to include post approval safety information including rare reports of death and a caution to practitioners that dogs should have a negative test for heartworm before administration.

Despite these label changes, FDA is still receiving unexplained adverse event reports, some of them severe. FDA's concern is based on voluntary self-reporting to FDA by veterinarians and owners whose dogs have suffered adverse drug experiences (ADEs) to ProHeart®6 (which contains the drug moxidectin) as well as the mandatory reporting of adverse events by Fort Dodge Animal Health.

Fort Dodge Animal Health has agreed to recall any product that has already been distributed to veterinarians.

As of August 4, 2004, FDA's Center for Veterinary Medicine (CVM) had received 5,552 adverse event reports for ProHeart®6. The actual number of adverse events is likely even higher because studies show that only a fraction of actual ADEs are reported.

The Agency has observed an increase in the number of cases associated with liver and bleeding abnormalities followed in some cases by death.