ProHeart 6

Proheart6
This week I’m going to tackle a controversial type of heartworm prevention. The hospital is considering the 6-month heartworm prevention injection for regular use again (ProHeart 6). This product was temporarily pulled from the market in 2004 due to concerns about safety. I’m going to spend some time today going over the history on ProHeart 6 and sharing some research data that examines the weight of any concerns about adverse reactions to the product.

ProHeart 6 is a specialized medication that allows the slow release of its active ingredient from the injection site over 6 months. The active ingredient is moxidectin. That same medication is found in Advantage Multi (made by Bayer Pharmaceuticals). The product was initially introduced by Fort Dodge in 2001. Fort Dodge had gone through all of the required FDA studies to have the product licensed for use in the US. Proheart 6 didn’t show any significant adverse effects, so it was put on the market. Veterinarians began using it extensively within a very short time. Millions of doses were administered all over the US. Many other countries also used ProHeart 6, including those in Europe, Asia, and Australia. In some places, ProHeart was licensed for 12-month protection (the dosing was different in those places).

Any time a new medication is released, a far larger number of patients receive it than during the safety and efficacy studies. Inevitably, this wide range of patients is a different population than in the safety studies. Dogs that may have had other illnesses, dogs of various ages, a wider range of breeds, use of the drug when vaccines are administered, other concurrent medications, etc. are all factors that contribute to differences ‘in the field’ as opposed to in the lab.

Concerns began to show up that ProHeart 6 was causing severe and serious reactions. These reactions included liver damage, autoimmune anemia, vomiting, anaphylactic reactions, and in some cases, deaths. The internet exploded with web pages (many of which are still up if you search) discussing the thought that “Proheart 6 is killing dogs.” At that time, no one was sure whether there was merit to this association or not. Bear in mind that there’s a difference between association and causation.

Fort Dodge voluntarily pulled ProHeart 6 off the market in the US in 2004. The equivalent oversight boards in most other countries did NOT recommend a recall of the product. Only South Korea took it off the market. Canada did NOT take it off the market. Four million doses were given in Australia. Europe had 3 million, and Japan 2 million.

A study published in 2005 used data from the Banfield vet hospital chain to examine whether ProHeart was associated with any increased risks, more reactions, or was causing deaths. The study used data from 1.93 million dogs, which is a very large sample size. It compared reactions from 2 oral heartworm preventions, ProHeart 6, and vaccinations.

This study led to a LOT of interesting comparative results. Overall, though, ProHeart was not implicated as a reason for increased rises in illness or disease or major reactions. The death rate per 10,000 encounters was NOT higher with ProHeart 6 patients, with or without concurrent vaccines. Concurrent drug use (NSAIDs, steroids) were associated with increased risk. There was an increase in some one type of cancer with dogs that received ProHeart 6 (mast cell tumor). The highest increase in problems came from pets receiving vaccinations. That may not surprise you if you slogged through the immunology posts with me! :)

The FDA allowed ProHeart 6 to come back on the market in 2008. As far as I’m aware, no change was made to the formula. Some very specific rules were placed that limited the types of patients that could have ProHeart 6. Pets had to be under 7 years old to get the product. Bloodwork had to be done BEFORE getting ProHeart 6. It had to be given on a separate visit from vaccines. Caution was advised for any dog with other types of allergies. Any animal with a history of weight loss could not get ProHeart 6. Vets had to have a 1-hour training session online and pass a small test to be allowed to order ProHeart 6 for use. We briefly used it at Pet Authority at that time, but clients were not very interested in jumping through all of the hoops, so we stopped offering it.

At no time did we see severe reactions to ProHeart 6 (even before it was recalled). We had no deaths that we can attribute to ProHeart 6.

Recently, Pfizer bought Ford Dodge. Pfizer now owns and manufactures ProHeart 6. The conditions I described above no longer HAVE to be followed, though Pfizer is, of course, recommending that veterinarians carefully choose which pets get ProHeart 6. We don’t routinely vaccinate animals that are sick or debilitated, so ProHeart 6 won’t be given to patients who shouldn’t be getting it, either.

We’re very likely to start stocking and offering ProHeart 6 again at Pet Authority. We feel the product is safe, and it’s a tremendous asset for some clients and patients. Only about 46% of clients remember to give their dogs heartworm prevention every month, so ProHeart 6 gives us an opportunity to make sure those dogs aren’t at risk. We’ll discuss the risks and benefits with all clients, the same way that we do for any other medications we give.

If you’re interested in that study that used the Banfield records, click here.

If you’d like to see the 2008 “Risk Minimization Action Plan” by Fort Dodge for the reintroduction of ProHeart 6, click here.

If you’d like to see the ProHeart 6 web page, click here.

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31 Comments

Filed under medication, parasites, practice

31 responses to “ProHeart 6

  1. Chris

    Long-lasting heart worm protection is a good thing. My dog is close to 7 years old now and has epilepsy, so I doubt you would consider her to be a candidate for ProHeart 6. We have no trouble remembering the monthly dose, thank goodness. Always one to err on the side of caution, I’d probably watch what happens with general distribution in the U.S. this time around, and then wait to see which method you recommend for my dog.
    As with all the pros and cons of vaccines, I’m really glad you studied, so that I don’t have to :)

    • I tend to be extremely picky about using new medications – I want to see the research data, efficacy and side effects before I put it to use. Dr. Williams is equally careful if not moreso. The strange thing with ProHeart is that we probably wouldn’t have stopped using it because we hadn’t seen any problems with it. That study seems to indicate that there really were very few risks in the larger pool of patients. The trouble of course is that if it’s YOUR dog who experiences an adverse reaction, you’re the one who has to suffer the consequences. It’s hard to argue safety with an owner in that case, not to mention inappropriate.

      I believe that if the product is administered correctly (proper needle size, proper patient selection), we’ll see a good safety record. We’ll certainly keep everyone informed as time goes on.

  2. Janet

    Our perfectly healthy 4 year old golden retriever received a dose of pro heart 6 nine days ago. Tonight I left him at a pet emergency hospital hooked up to IVs, he began tremors, foamy phlegm and literally “collapsed” earlier today.

    • I’m sorry to hear that your Golden is so sick! Hopefully he’ll pull through! Would you be willing to provide more background on what happened to him? What was he doing before and during the sudden collapse? Were there any other medications on board? Where were you/he when the collapse occurred? Any history of heart problems, seizures, or other medical issues?

      Thanks for taking the time to read the blog. I’m more than willing to offer whatever information I can to help you and your dog.

  3. Elizabeth

    My perfectly healthy 2 year old Min Pin received a dose of pro heart 6 back on Aug 28th, 2012 no previous health conditions of any kind. Over the last few weeks since the injection I noticed him losing interest in food.. the first concern was the loss of appetite. The vet kept saying a healthy dog won’t starve himself. So i shrugged it off… I offered his food at the same times daily and just didn’t stress out if he didn’t eat all of his food. Then i noticed his spine and tailbones started showing out of the blue – it was like one day i didn’t notice it and the next day he looked so unhealthy. So i attempted several different things to get him to eat, and took him to the vet this morning and dropped him off for his routine teeth cleaning.. I expressed my concerns to the vet over the last 4-5 weeks since getting the injection and left him at the vet since they have to put him to sleep to clean his teeth and all. I had only been home a couple hours when the vet called and said that they ran bloodwork on him and there were a couple very serious concerns. Next, i’m told that he needs to see a specialist and have an ultrasound possibly a biopsy done. Then i’m informed in the same phone call that the vet has already contacted Phizer, who has assigned my dog a case # , and is paying for all the testing and/or treatment. This really bothers me. Why are they so willing to pay for everything? To me is shows lack of confidence in their product, not customer service. Customer service should be to have an antidote or reversal medicine available for all drugs administered to our animals. The issue I have now, is that we have 5 months to go before the injection wears off. The vet i take my dog to is Banfield, and i’ve used them for years and i think they are wonderful, and i am taking full responsibility for this, as i agreed to this form of heartworm prevention. I had the option to choose another method, but didn’t because i trusted that precautions are taken on these drugs, and they are safe. All that my vet knows is that the specialist has them doing liver function tests on my dog today and that i need to have him at the internal medicine specialist first thing tomorrow morning. :( Please be cautious of this drug, and inform patients of true live instances where people have lost their dogs due to this injection. My dog is still alive, right now and i hope and pray that he will pull thru this, but i’ve read on the internet where alot of people lost their healthy dogs within weeks or months of this injection.

    • I’m sorry to hear that your dog is sick! It’s such a difficult thing to face no matter the reason.

      Statistically speaking, ProHeart is safe. Unfortunately, when your dog is the one who is sick, the statistics don’t matter. It’s possible that the product caused the problem. There are so many factors when looking for the “why” of an illness like this, it’s hard to pin down what the truth is. It may even be more than one factor. The diagnostics recommended by your vet and Pfizer are going to provide you with a much clearer picture.

      I wish we could have an effective antidote for every medication. It would really help us out as vets, and humans! Medications undergo stringent testing to determine safety and efficacy, regulated by the federal government. Even so, we must acknowledge the fact that no study will have enough data to capture every possible side effect or individual patient variation. Some things we just can’t know ahead of time.

      At some point we have to make an individual decision as to the intent of the people providing the treatment: do they act out of altruism and the best intentions, or are they protecting less noble pursuits?

      I sincerely hope that your dog pulls through, and I just as sincerely hope that you are ale to find a specific answer about what caused his illness. Having reported the illness to the company, you and your vet have helped other patients as well.

      I don’t see where guilt will help you, especially if you’re second-guessing yourself. You did what you thought was best, based on your vet’s good judgement. A very serious event in your pet’s health has happened, and the first step is to try to diagnose the specific problem so it can be treated. You’re doing exactly that, and it’s the right thing to do.

      I appreciate you sharing your experience with the other readers. It will help others.

      Please keep us updated on your dog’s progress.

    • Gomes

      In memory of “Sam”
      We lost our 9 year old healthy golden retriever to the Proheart 6 shot back in 2005. He received the shot just weeks before Fort Dodge had taken the drug off the market. I was shocked when I heard that it was back on the market. Our golden had received the shot more than one time. The first time he had a minor reaction of vomiting, but, we had not attributed that to the shot. We merely thought he had eaten something that hadn’t agreed with him. When it was time for the second shot (6 months later) it was a different story. Briefly, our story started out much like yours. Fort Dodge agreed to pay all the vet bills for our “Sam” at Tufts Vet Hospital in MA if we would agree to a neocropsy of “Sam” if he died. Of course we agreed never believing that could be the end result. They had to treat him with steroids to get him to begin to eat and gain a little weight back and to assist in normalizing his blood cell count. It appears the Proheart 6 shot had caused an auto immune response. The suffering the Proheart 6 shot caused our healthy dog was unspeakable. We had hoped that if we could keep him alive and eating that 6 months later the shot would wear off and he would be ok. That is not what happened. The steroids that were keeping him eating and alive eventually (after 5 1/2 months) caused some kidney weakness and he suffered clotting of his blood. A blood clot travelled to his lung and we were forced to put him to “sleep”. We agreed to have the neocropsy in the hopes that we would never see this Proheart 6 shot on the market again. The neocropsy was completed by Tufts Vet Hospital and conclusive that “Sam” had in fact died from side effects/reactions caused by the Proheart 6 shot. I hope that out story reaches many caring pet owners that are not aware of the side effects of the Proheart 6 shot, as I would never wish to see anyone go through what our “Sam” had to go through and the suffering that Proheart 6 caused him and our family.

  4. At least it sounds like you are following the proper protocol… my vet did not. My dog, Jack died. You can read our story here: http://ashleysassaman.wordpress.com/

    • Thanks for sharing the link to your story. I’m sorry about Jack — it’s horrible to lose a beloved pet unexpectedly. I also greatly appreciate the objective way you went about looking for answers and drawing conclusions. You were very fair both about your concerns and your expectations for your vet, Pfizer, and the State Board. I hope that time has helped ease the pain for your family. It’s awful that a family so dedicated to doing the right thing by protecting their pets from heartworm had to endure such an ordeal.

      Our practice has stopped using ProHeart 6. We simply didn’t have enough owners interested in having it administered after we discussed the safety concerns and presented the consent form. I personally didn’t have any patients develop serious problems (I had a couple that were sore where the injection was given); the other associate at our practice has seen a dog have a lethal ProHeart injection at another practice she worked for. We also feel that there are other products that offer a better spectrum of parasite prevention.

      Thank you again for sharing your story, and for reading this blog.

  5. Denise

    BEWARE!!!!!
    My 4 year old Boxer is currently in the emergency room due to his 3rd Proheart 6 injection. My Vet followed Protocol and Einstein was extremely healthy and happy until the injection administered October 18th. We currently do not know if he will live or die and there is no counter treatment for a dog who has a bad reaction. The drug is in their system for a full six months. It is definitely not worth the risk. There are too many was to remind yourself when your dog is due is heart worm pill each month. Don’t be lulled into complacency by the lure of convince.

    • Our hospital has stopped carrying ProHeart 6 entirely; we just didn’t have the demand for it, and the potential problems were severe enough that we decided there are better ways to prevent heartworm disease. I’m sorry that Einstein is in such rough shape! I hope he pulls through! Please let us know how things turn out.

      • Denise

        Einstein passed away the day after my previous post. He started with depression, face swelling, loss of appetite, weight loss, neurological problems, nervous system problems, and finally his platelets dropped too low to control and he could no longer clot blood. he died a painful slow death over a period of 3 and 1/2 months. We watched in horror and helplessness until the Auto immune problems caused him to begin internally bleeding into his own lungs. We made the painful decision to have him put to sleep Sunday Feb. 3rd. We could not watch him suffer such a cruel existence any longer. We have reported his death to the FDA and to Zoetis (the new name of the pharmaceutical company that produces proheart 6) We also reported the issues to Banfield, who has been our family Vet for over 10 years. They are continuing to carry and administer pro heart 6 so we are no longer continuing to use Banfield and have selected a new Vet for our other two dogs.
        I hope by sharing our story others will be discouraged from using proheart 6

      • I’m so sorry to hear that Einstein passed away. Putting him to sleep had to have been an absolutely crushing decision for you to have to make. :( I would have made the same choice, for what it’s worth.

        I appreciate you taking the time to comment here again, and to share your cautions with other pet owners. You’ve done as much as you can do in reporting the events to Zoetis and the FDA. I’m guessing that you haven’t had much of a response from either of them?

        We are NOT using Proheart at our practice.

        Thank you again for keeping the blog updated. You have my deepest sympathy for your loss.

  6. christy

    i am so scared! my 4 year old healthy pug mix got the proheart shot for the first time with her vacs today at 3pm. by 5pm her face was swollen twice the size. i took her back to the vet, he gave her a shot and sent me back home. all night she has not been herself-just laying around and her face is still swollen half the size. i’ve been reading about proheart the last hour and realized my vet never told me about any of these terrible life threatning side affects! he never gave me a brochure or anything. he just said instead of heartguard chewables, do i want a 6 month shot instead? i asked what the difference was and he said no difference, except it might make her throw up. he was so nonchalant about it! omg i hope dakota pulls through but after reading all of these heartbreaking stories i’m scared for her!

    • I can absolutely understand why you’re so scared! Try to remember that the vast majority of dogs that receive ProHeart 6 do just fine. A reaction doesn’t automatically mean the worst.

      The reaction you’re seeing could have been from the regular vaccines, too. Facial swelling can take several hours to begin to go away once it’s present (even with a steroid or benadryl injection on board).

      If you don’t see improvement by the morning, you should call your vet right away to have Dakota examined again. It would be a good idea to have some bloodwork and a urinalysis run to establish a baseline, on the outside chance that she will have more trouble.

      Check on her frequently tonight. If the swelling gets worse, or she has vomiting/diarrhea, or seems weak or sicker for any reason, take her to an emergency hospital for an examination. You can also lift up her lip and look at her gums above her teeth. In any area without black pigment, the tissue should be nice and bright, rich pink. If it looks pale, gray, white, or blueish, you should take her to an emergency hospital. (Also, if you press on the gums, the blanched out white should return to pink in about 1 second. If it’s 2-3 seconds, she needs to be examined.)

      I would absolutely NOT give her ProHeart again, and you should consider giving her Benadryl before any regular vaccine appointment.

      Please let us know how things go!

  7. Sharon Trautsch

    I just got my dog a proheart6 injection a few weeks ago. She has been having bloody diareah intermittantly, so I looked up proheart6 on the internet. What I found is disturbing. First of all, it should not be given to dogs over 7 years old. My dog is almost 13. Secondly, it should not be given wuthin a month of vaccinations. They vaccinated my dog tge same day. I’m pissed off that they could’ve endangered my dogs life, if they would’ve stuck to prodacol my dog wouldn’t be in this situation.

  8. Lauren

    Thank you for offering a level headed, rational, and scientifically based analysis of this preventative. I feel awful for everyone who has lost a pet when using this preventative, but your analysis made me feel secure in administering it to my 2 year old Cane Corso (although not in conjunction with her vaccines). Again, I am sorry to anyone who lost a pet, but it does seem that statistically speaking, this is a safe means of prevention.

  9. reagan miller

    I have a 2 and half year old blue pit named dre, we took him in last thursday for a check up and got a clean bill of health, I asked them about the proheart injection because they wanted to give it him and said there a very rarely any side effects and I assumed it would be a safe medication to be administered. About 4 hours after receiving the injection dre’s eyes began to swell so we immediately took him to the emergency vet hospital, by time we arrived his head was covered in hives, they ended up giving him benadryl im and dexamethonone im and I believe two other po steroids. After that he continued to be somewhat itchy but he no longer had hives or facial swelling.
    the next day I called our vet and he wanted to do some blood work and ua, the ua was negative but he did have some abnormal labs. his potassium was low and his wbcs were elevated, I believe his lymphocyte and neutrophil count was high too. anyways what im getting at is the vet asked me when I wanted to have labs drawn again, he offered 3 weeks so I said 2, im concerned because my dog seems not to be lethargic but weak, he has had no diarrhea so far or vomiting, he has had increased urination and thirst, im wondering how often we should have labs drawn over the next 6 months, I really want to have his labs rechecked in 1 week and then possibly again in a week after that. Im concerned about an earlier post about a drop in platelet count, if that were to happen when might you see a decrease in platelets after the injection has been given? and when might you see an anaphylaxis reaction? he has still been playful just seems to be weaker then he did before the injection. his gums are pink and blanchable but this is only day 3 after receiving the injection.

    • I think that a week after the injection is fine to run some bloodwork. Another set a week after that is also fine. Ultimately, I think that there are very few vets that would turn down more information if an owner is willing to spend the money. I’m sure they’ll run it if you ask. In order to check the kidneys thoroughly, have them run an analysis of his urine, too.

      Please keep us posted on Dre’s progress, ok? I hope he recovers quickly and completely!

  10. Lori

    My healthy 9 year old male boxer, Copper, died from seizures after getting his first ProHeart 6 shot 3 weeks ago. We have been on the Banfield Wellness plan for several years and he was in for his 6 month physical along with our 3 year old pitt bull. The vet recommended the shot for both of them – we were not aware a 6 month heartworm shot existed – but it seemed like a good idea and we had them given the shot. Unfortunately, we did not receive an information sheet about any potential side effects or any caution of the history of the medication. Three days after getting his shot, we found Copper on the kitchen floor collapsed on his side laying in his urine. He had the classic symptoms of a seizure. After a few minutes, he snapped out of it and appeared to be fine. We kept an eye on him for the next few days and all was well so we thought it was an isolated incident. Two weeks later, Copper had another seizure and collapsed. Within a few minutes he had stopped breathing – died in front of my husband and I and are two young daughters. We were horrified and thought it was a tragic death – perhaps he had a tumor or something we never knew about. We called Banfield to let them know that Copper had died that morning. Given the suddenness of his death, my husband casually asked if there were any side effects of the hearthworm shot he had been given….she replied vomiting and seizures were the most common. He told her that Copper had both of those symptoms – silence on the other end of the phone. I called Banfield to cancel his Wellness Plan and all they told me I pay for the remaining 5 months of his plan. Can this get any worse? Yes. After reading the client information sheet on Zoetis website tonight, we are simply horrified at the negligence of our vet. Had we received that sheet or any other verbal or written information, we would have immediately contacted the vet after his first seizure 3 days after the shot. We never connected them to the heartworm shot – but Banfield did. I am still waiting for Banfield to contact me, I have called them repeatedly since Copper died 5 days ago. I finally got a call back from my vet today – apparently she never got my messages until today. I have also contacted Zoetis to report his death – all I got was a case number. Given the history of this drug, I would caution all owners – having your dog be a statistic isn’t worth it. The irony of paying for a preventative wellness plan that then resulted in him getting a preventative shot – in the end all that was prevented was him continuing to live.

    • First and foremost, I’m terribly sorry for your loss. Copper was clearly a well-cared-for and deeply loved family member. I’ve approved your comment in the hope that others may find this post so they can make an informed decision on the care of their own pets.

      You’ve taken all of the right steps for reporting an adverse event (language that is sadly understated given the seriousness of the consequences for Copper). You can also contact the FDA to report this at this web page: http://www.fda.gov/Safety/MedWatch/HowToReport/default.htm

      This may sound insensitive, but I assure you that I mention this only as a means to getting answers. Did you permit a post-mortem exam of Copper, or submit any tissues to the pathologist for examination?

      Again, my heartfelt condolences. Thank you for having the strength to share your experience with others.

  11. Chris Miner

    This is so sad. Let me add my heartfelt condolences to you and your family. We’re supposed to be able to trust the treatment our vet recommends. Your courage in sharing Copper’s story may very well save other dogs from the same fate. His memory lives on.

  12. Virginia Easterday

    My dog is very sick too after a pro heart 6 injection. He is 8 years old and never been sick a day in his life. Now vomiting bile and lost 2 pounds in the first day alone. No interest in food, laying around all the time. This is wrong! Pfizer has duped the vets to make money. I am scared what is going to happen to my dear little guy. Will he ever recover?

    • Some patients do recover, yes. If you haven’t taken your dog to a veterinarian for an exam, bloodwork, and urinalysis, please do so as soon as possible! He may need to be hospitalized for intravenous fluids and other supportive measures.

      I wish you the best for his quick recovery!

  13. Virginia Easterday

    Yes, I did take him to the vet the next day and they hydrated him with a subcutaneous injection and gave him a shot for upset stomach. The next day he was a little better and able to walk again and drank lots of water. In the next days better and better and back to normal with a good appetite on day 5. We are so thankful that he is still with us thought we were going to lose him. I feel he has recovered but concerned as the drug slow releases over time. The vet was extremely concerned. I think it opened his eyes as to how bad it can be for some dogs. Lots of posters for Proheart 6 all over the office. Pfizer has done a great job marketing this poison. Beware beware.

    • Good news!! I’m so relieved that he’s doing okay. Tough pooch. :)
      Keep an eye on his bloodwork over the next 6 months so you can track changes, and be sure your vet has reported this adverse event to Pfizer/Zoetis *and* the FDA.

      I wish you continued good luck and healthy recovery for your dog. Thank you for taking the time to follow up!

  14. Leslie

    I am curious, i have two boxers, one is 4 years old and the other is just over a year. I have been debating about giving them the proheart 6 being the fact that I am sometimes late on giving it to them (not by more then a week) but i would be devastating to my entire family if something ever happened to them. My dogs are my children along with my other two (two legged children) and my co-workers and i don’t want anything to happen to them. I just took them in today for their yearly shots, but they are due on the 15 of this month for their heartworm treatment. I am not sure if i should give them the proheart 6. They are both very healthy dogs, we run 3 miles every morning and evening. I am just asking for your professional opinion on whether i should give my boys proheart 6?

    • Personally, I wouldn’t give Proheart to my dog or a family member’s dog. I think that with the vast number of ways to help stay on schedule with oral prevention, it’s a far safer way to go. There are apps for Android and iOS phones that will remind you monthly to give prevention. You can always set up a repeating reminder in your phone, tablet, or desktop computer to do that as well. :)

  15. Chris Miner

    That’s good advice. It’s obvious how much you love your dogs. Too many healthy dogs have died. Figuring out a system to keep your boys on schedule is a far better idea. Good luck :)

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