Wherever there are mosquitoes, dogs can be infected with potentially fatal heartworm disease. The problem is that about half of all dogs don't take a monthly heartworm preventative in the first place, and about half of those who do periodically skip at least one dose, which can make them susceptible to the disease. That's why when an injectable product called ProHeart 6 was released in 2002, the buzz was palpable, in a good way. Veterinarians knew they had a product that would protect dogs, with a single injection lasting for six months.
In 2004, under some pressure from the U.S. Food and Drug Administration Center for Veterinary Medicine (FDA CVM), the drug was voluntarily recalled by the manufacturer, Fort Dodge Animal Health.
Tragically, some of what went on was very real. Dr. Michael McFarland, group director of Companion Animal Veterinary Operations for Zoetis, says, "Fort Dodge re-assessed their manufacturing process, and they noted batches with inappropriate levels of a solvent residue in the product."
Having said that, the American Heartworm Society (AHS) and various experts were asked to review every report of an adverse reaction to ProHeart 6 that was filed.
"Some (reactions as a result of the drug) were real," says Dr. Sheldon Rubin, then a AHS Board member. "But others weren't. It's the way things are reported in this country. If an individual thinks their pet was harmed by a drug, a report can be made. One example is of a dog who had the (ProHeart6) injection, then rode home in an open pickup truck, jumped out and was hit by a car. The owner claimed the drug was at fault because the dog had never done that before. Clearly, that (report) and others were unfounded."
In 2009, Fort Dodge brought back the product but under a FDA CVM RiskMAP (Risk Minimization Action Plan), which means that the drug would only be given under careful consideration and following specific guidelines. In this instance, pets with known drug allergies or serious health issues and older dogs could not be given the drug. Also, only veterinarians with special training could give the drug, and only if dog owners signed a consent form, acknowledging risks vs. benefits of ProHeart 6.
At the time the action taken by the FDA, CVM was considered harsh, according to several veterinary and epidemiology experts who reviewed the adverse events.
"We all know this drug is now safe, if veterinarians use it appropriately," said AHS Board Member Dr. Jorge Guerrero at the time.
Less than a year later, Fort Dodge was divested by parent company Wyeth (which had nothing to do with ProHeart 6). Other companies swallowed up various Fort Dodge products, and Pfizer Animal Health took on ProHeart 6. Earlier this year, Pfizer spun out a stand-alone animal health company called Zoetis.
All through the corporate give and takes, ProHeart6 continued to be sold to dog owners without fanfare, and tracked very carefully. In late August, the FDA-CVM announced revisions to ease the ProHeart6 RiskMAP based on a review of the product's excellent safety history since the RiskMAP was put into place.
So, the FDA-CVM is now relaxing the restriction. Now dogs of any age (over 6-months, and in good health) may receive the drug. Veterinary technicians trained in the drug's use can administer the injection (as they can routinely give vaccines and injectable antibiotics, for example).
"Most relevant, dog owners will no longer be required to sign a consent form," says McFarland. "It remains our responsibility and the responsibility of veterinarians to make pet owners aware of risks and benefits of any drug. But it's human nature that when you're asked to sign such a form, you may become inappropriately fearful."
Aside from protecting dogs against heartworm for six consecutive months, another benefit of ProHeart 6 is its twice-annual injection requirement.
"We now know you will interact with your veterinarian twice a year, and we know when that happens lives are saved," adds McFarland. "There are things picked up on a physical exam that a pet owner can't recognize at home." An early prognosis may result in a better outcome for the pet. And might even be life saving.
However, unlike most monthly chewable heartworm preventives, ProHear6 does not protect against common intestinal parasites (whipworm, roundworm or hookworm), though it does treat hookworms. Ask your veterinarian about appropriate intestinal parasite protection to match your geography and your pet's lifestyle.
McFarland adds, "Over the course of my career, I've seen many, many dogs die of heartworm disease. And it's one of the most tragic things you see as a veterinarian because you know it's preventable."
(Steve Dale welcomes questions/comments from readers. Although he can't answer all of them individually, he'll answer those of general interest in his column Send e-mail to PETWORLD(at)STEVE DALE.TV. Include your name, city and state. Steve's website is http://www.stevedalepetworld.com; he also hosts the nationally syndicated "Steve Dale's Pet World" and "The Pet Minute." He's also a contributing editor to USA Weekend.)