June 17, 2008

Risks Have Been Minimized

By Bernadette Dunham

The return of ProHeart 6 (moxidectin) provides a good example of how the FDA's scientists tackle the toughest challenges.

ProHeart 6 is the first veterinary drug marketed under a risk minimization and restricted distribution program that allows veterinarians to weigh the risk of heartworm disease in their canine patients with the benefits of a six-month injection that maximizes protection.

About 30 FDA-regulated products for humans are marketed under similar risk management programs. Such programs help ensure that health care professionals have access to products that are safe and effective, that patients are aware of potential risks, and that the products are used properly.

ProHeart 6 was first approved by the FDA in 2001. In the months after approval, the FDA and drugmaker Fort Dodge Animal Health received reports of adverse drug events from dog owners and veterinarians.

After reviewing more than 5,000 adverse drug event reports, the FDA asked Fort Dodge to remove ProHeart 6 from the market. The company did so voluntarily in September 2004. Fort Dodge attributed the adverse events, mainly allergic reactions, to solvents used in manufacturing.

Since then, the FDA, Fort Dodge and veterinary health care professionals have explored virtually every aspect of problems associated with ProHeart 6. The FDA group that evaluated ProHeart 6 included toxicologists, epidemiologists, immunologists, pathologists, chemists, veterinary medical officers and statisticians. The review process respected each team member's contribution and valued diversity of thought to arrive at the most sound decisions possible.

Education, communication and surveillance are the pillars supporting the ProHeart 6 risk minimization and restricted use program. Product labeling and other materials include warnings not to give the drug within one month of vaccinations, and to use the product with caution in dogs with pre-existing allergic diseases. Dogs that are sick, debilitated, underweight or that have a history of weight loss should not be given ProHeart 6.

Veterinarians must register with Fort Dodge and take a Web-based company training course, obtain consent from dog owners and report any adverse events to the company. Dog owners will get access to ProHeart 6 if a veterinarian decides it's appropriate.

Dr. Bernadette Dunham is director of the FDA's Center for Veterinary Medicine. (c) Copyright 2008 USA TODAY, a division of Gannett Co. Inc. <>