Misty, the 10-year-old Golden Retriever who inspired the Senior Dogs Project

The Senior Dogs Project
..........."Looking Out for Older Dogs" ...........

"Blessed is the person who has earned the love of an old dog."
Sydney Jeanne Seward



Proheart's Back Story -- Disturbing Details; Advice to Hold Off Using It

While it's true that Proheart 6 has been reintroduced, it's important to understand the history of the drug. As the Nathan Cummings Foundation states, "It's a disturbing tale for anyone who relies on pharmaceutical companies and the FDA to ensure that medicines for animals and humans are safe, one that raises questions about the conduct of a major corporation and its federal regulator."

Please watch a video in which a veterinarian describes the problems with Proheart6 and what's happening with it now. "They claim it was totally reformulated," says Dr. Pinney of Veterinary Insider. He adds, "I'm not sure I believe that." He recommends holding off on using Proheart6 until there has been more experience with the supposedly "reformulated" drug.

Proheart is Re-introduced as Proheart 6.....Is It Safer?

According to an informed veterinarian, "Proheart caused more deaths in one year than all of the oral heartworm preventives combined did in ten years. When the FDA notified Pfizer that their drug was causing a problem, the manufacturer claimed it was due to the vaccines' being given at the same time. The FDA looked at the data again and told them the dogs involved had been getting their vaccinations all along and the only difference was the Proheart. That's when the FDA informed the company of their intent to pull it and the company then voluntarily took it off the market." Proheart now back on the market, but, according to our source, it is still the same drug, Moxidectin. The website, drugs.com, you'll find this warning:

Because Of Its Potential For Serious Adverse Drug Reactions And The Absence Of Identifiable Risk Factors Associated With Those Reactions, Proheart 6 Is Only Indicated For Those Dogs In Which Alternative Preventatives Cannot Be Effectively Administered.

Our resouce tells us, "One problem with Proheart is that it is a six-month injection. Heartworm preventives like Interceptor or Heartgard are out of a dog's system in a few days; their protection goes backward and covers the 30 days before the medication was given, does not protect for the month after administration. They are essentially 'catch up' drugs, catching a dog up for the previous month. If a dog has a problem with the drug, it's short term as the drug is out of them in a few days. Not so with a six-month injection. If a dog has a problem with it, the Proheart is still there for six months."

September 4, 2004 -- ProHeart6 Withdrawn from Market

From a news release appearing on the FDA website:

Fort Dodge to Comply with FDA's Request to Recall ProHeart 6 Injectable Heartworm Product from the Market Due to Serious Health Concerns

Fort Dodge Animal Health, of Overland Park, Kansas, at FDA's request, has agreed to immediately cease production and 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. Read more......

Reports of Side Effects

We first began receiving reports of side effects of ProHeart6 in the fall of 2002, as follows:

"My name is Janice Storey. My dog, too, became ill because of the ProHeart6 shot and died on October 17. Along with Myra Kirkland, I am on a mission to save other dogs and make it mandatory that veterinarians present the ProHeart6 label for review prior to a consumer making a decision about this shot. My dog, Trouble, received his annual vaccinations along with the ProHeart6 shot. He began coughing shortly thereafter and was dead within weeks." jstorey1@swbell.net

Since that time, a site has been created that posts reports of

History of ProHeart6

ProHeart6 (made by Fort Dodge Animal Health) was introduced to the market in 2001. It is an injectable form of heartworm medication that a veterinarian administers every six months to protect a dog from heartworm infection. A description of heartworm disease and the way in which ProHeart6 works can be found on the Fort Dodge website.

Although trials of the medication indicated it conformed to the government's safety standards, it was only after the drug had been used more widely and over a longer period of time that adverse side effects, including death, began to appear in increasing numbers. Dr. Victoria Hampshire, adverse drug events coordinator for the FDA, on November 1, 2003 made the following comments: "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."

At the end of August 2003, Fort Dodge distributed a "Dear Doctor" letter to veterinarians with updated information about the drug. Although stating that the number was low, Fort Dodge notes, "Death has been reported in approximately .0025 percent of the doses sold into veterinary clinics." It is interesting to note that, even during clinical trials, three dogs died when given the shot. Two deaths were attributed to the dogs' "being older" and the third to the dog's being "underweight."

The letter to veterinarians from Fort Dodge advised that the following was being added to the label information for ProHeart6:

"Cardiopulmonary signs such as coughing and dyspnea may occur in heartworm-positive dogs treated with ProHeart6."

And, under the "Precautions," the following change was made:

Removal of the statement, "At the discretion of the veterinarian" before the sentence, "Infected dogs should be treated to remove adult heartworms."

It is extremely important, if you suspect your dog has had an adverse reaction to ProHeart6, that you report both to Fort Dodge Animal Health and to the FDA. The toll-free number for Fort Dodge is: 1.800.533-8536 . You can file a report with the FDA by telephone at: 1-888-332-8387 (or 1-888-FDA-VETS)


You may also report an adverse drug experience using a form that is available on the FDA website. Click here for the form.

If you you would like to be in touch with others whose dogs have experienced a negative reaction to ProHeart6, here are the people to contact:

  • Myra Kirkland, MKirkland@carolina.rr.com
  • Janice Storey, jstorey1@swbell.net
  • You may also wish to join the "doghealth2" E-mail list, which has ongoing discussions about canine medications and health. doghealth2@yahoogroups.com