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U.S. Department of Health and Human Services

Animal & Veterinary

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FDA Announces ProHeart® 6 Return to Market

by Jon F. Scheid, Editor
FDA Veterinarian Newsletter March / April 2008 Volume XXIII, No II

ProHeart® 6 (moxidectin) Sustained Release Injectable for Dogs, a unique heartworm preventive product, is returning to the U.S. market.

The drug’s sponsor, Fort Dodge Animal Health, voluntarily removed the product from the U.S. market and ceased pro-duction of it in 2004 because of the Food and Drug Administration’s concerns about reports of adverse reactions to the drug. The reported reactions, which included numerous deaths, were unanticipated and unexplained. FDA requested that the drug be removed from the market until the company and FDA could further investigate the situation and resolve con-cerns.

Fort Dodge Animal Health has changed the manufacturing specifications for Proheart® 6 to minimize the inclusion of re-sidual solvents in the final product. Also during this time, the number of adverse event reports from international markets, where the product remained available, has declined.

Fort Dodge Animal Health, a division of Wyeth, is based in Fort Dodge, IA.

In June 2008, FDA approved a Supplemental New Animal Drug Application for ProHeart® 6 that revises the label and client information sheet to include additional warnings, precautions, and adverse reactions. Additionally, FDA concurs with Fort Dodge Animal Health’s decision to market ProHeart® 6 under a risk minimization and restricted distribution plan. Only veterinarians who have undergone in-depth training from Fort Dodge Animal Health will be allowed to obtain the drug, which will be available only from the sponsor. After a veterinarian has undergone the training, he or she will be able to purchase ProHeart® 6 as needed.

Heartworm disease is caused by Dirofilaria immitis and is transmitted via mosquito bites. Dogs show no signs of the disease until the heartworm larvae mature. The mature larvae gather in the right atrium and pulmonary artery of the dog, which can produce cardiopulmonary effects in the dog. Dogs suffering from heartworm infections can have a cough and can display a low tolerance for exercise. A dog with severe heartworm disease can die from it.

Veterinarians want heartworm prevention options because treating the disease is more difficult and puts a dog at greater risk than preventing the disease. For example, during treatment, the heartworm could break off, creating risks of clots and possibly killing the dog. Also, drugs approved to treat mature heartworms have low margins of safety.

ProHeart® 6 prevents heartworm disease in dogs for 6 months following injection. It is the only drug approved in the United States with a sustained period of protection. Many veterinarians want ProHeart® 6 available as an option when the dog’s owner is unable, unwilling, or unlikely to regularly administer the monthly oral or topical treatments that otherwise must be used.

Fort Dodge Animal Health has revised the product’s label. The label warns not to use the drug within a month of the time a dog receives vaccinations and not to use it in dogs with pre-existing allergic disease, including food allergies, skin allergies, and flea allergy dermatitis. In addition, the label states that veterinarians should not administer the drug to dogs that are sick, debilitated, underweight, or have a history of weight loss.

The post-approval section of the label has been updated to include reported adverse reactions, such as liver and blood disorders.

Dog owners will be required to sign a consent form before their dogs are treated and will receive a revised Client Infor-mation Sheet that includes updated safety information.

FDA says that owners who think their dogs are suffering from an adverse event from ProHeart® 6 should immediately contact their veterinarians, who can treat the dog for the problem. Under the risk minimization and restricted distribution plan, veterinarians will agree to submit Adverse Experience Reports to Fort Dodge Animal Health.