A veterinary blog for pet lovers, vet voyeurs and the medically curious...
Support Dolittler: Subscribe!
Search

Some of you may have personal experience with the once-popular canine heartworm preventative, ProHeart 6. It was marketed from June 2001 to September 2004, until the FDA recalled it after thousands of adverse reaction reports crossed its desks. And now, almost four years later, it's making a comeback (that's the plan, anyway).

According to the FDA, 5,552 ProHeart 6 reactions were reported after dogs received this every-six-month injection. 500 dogs died, though definitive causality in these deaths was not established.

Fort Dodge, the manufacturer, claims a total of 18 million doses were sold during this period, implying that the risk of reaction is one per every 3,242 injections.

I saw two of them. One was not terrible, just some mild muscle pain and a low-grade fever for two days. The other was comparably horrendous, LOTS of pain and a high fever for three to four days. Fluids and pain relievers treated both cases successfully. I’m not so sure we reported the first reaction (it was so mild and he wasn’t my patient) but I’m sure we reported the second one.

The generic name for ProHeart 6 is moxidectin. Fort Dodge stands by it. It’s been used in Europe and Australia for over a decade with relatively few complaints. The Aussies even use it in its ProHeart 12 form as a once-a-year heartworm preventative.  Beats heartworms, they say.

Here in the US, about 250,000 of our dogs are infected with heartworms every year. That’s in spite of the widespread use of heartworm preventatives.

Why? Because some of us refuse to seek preventative medical attention for our pets. And the rest of us who manage a heartworm-positive status for our pooches? We simply forget to give the meds as prescribed.

Fort Dodge says it seeks to cut into the latter group’s prevalence with an every-six-month approach. And it’s true, client noncompliance  is probably the biggest source of heartworm disease in this country these days.

Some vets like it, too, since it requires that owners come in and see the vet twice yearly (though most of us don’t charge for an exam at the same time).

But I’m largely unmoved. My position with respect to ProHeart 6 stands: The drug has its place. But it’s a very limited one in my practice.

Why?

1-Noncompliance is a major source of heartworm disease but by far the largest subset of this group includes those who refuse any preventatives at all.

2-Noncompliance in my area (where year-round heartworm meds are a must) means owners don’t come back in a timely fashion for their ProHeart 6 shot. (That’s what happened when we carried it, despite our reminders.)

3-The risk/reward axis is mighty high with ProHeart 6 relative to alternative means of heartworm prevention.

Then why would any vet use ProHeart 6?

Plenty won't. Yet despite my reservations, I likely will. That’s because some of my clients will swear there’s no other way they’ll consider using heartworm preventatives (yes, I swear I have clients like this). And, remember,  I live in Florida.

Fort Dodge is making sure any of us who plan to use this product at least understand their basic rules. Veterinarians can only access ProHeart 6 through a limited distribution approach. An online seminar must be completed before a veterinarian can place an order.

And that makes sense to me. Though I seriously doubt that any reactions were caused by veterinarians administering an injection incorrectly, as the company infers may have been the case in the past, setting a bar (even a low one like this) helps ensure we vets know what we’re in for when we use it.

Comments
Has Fort Dodge ever come out with an explanation for what exactly killed all the dogs with the "old" Proheart6 and how the "new" Proheart6 has been corrected for whatever that was?
# Posted By YesBiscuit! | 6/16/08 2:50 PM
Their statements have been very measured on this point. In the AP piece I cited, Fort Dodge has “concerns about how the [FDA] interpreted these complex data...Based on a thorough evaluation of FDA’s data and consultation with independent experts in veterinary medicine and epidemiology, Fort Dodge Animal Health stands behind ProHeart 6.”

In other words, they don't buy the severity and/or number of the reactions. They believe their significance was overblown by the FDA.
# Posted By Dr. Patty Khuly | 6/16/08 3:12 PM
Oops, sorry, I see I didn't exactly address your question properly. It's the same drug. Is its injectable base different? I don't think so but anyone else can correct me if I'm wrong. The only difference, from my understanding, is that the distribution will be limited to veterinarians who will be provided with explicit guidelines as to its use.
# Posted By Dr. Patty Khuly | 6/16/08 3:18 PM
If it's the same drug that killed so many dogs before, I won't be signing up.
Fort Dodge seems to think that by limiting its first-run to only "the best and the brightest" of dogs, consumers will be fooled into believing the product is safe if/when minimal reactions are reported. Savvy consumers know that for a drug to be "safe", it needs to work for MOST dogs in MOST conditions - not just the healthiest select few.
# Posted By YesBiscuit! | 6/16/08 3:27 PM
From what I understand Proheart 6 is being released with restrictions placed on it by the FDA. It can't be administered within a month of any vaccines, pre-admin blood work has to be pulled (but not reviewed), it can only be given to animals 6 month to 7 years of age, can only be given to healthy animals (no chronic disease), and should be used with caution in animals with allergic disease. The client is expected to foot the bill on the pre-admin CBC and chemistry (to be done before each dosing).
Fort Dodge is offering a temporary discount, something along the lines of 10%- that will not cover the separate office call required to give PH6 (seeing as it can't be given with vaccines), nor will it cover the blood work.
This is a trial phase as part of the FDA testing, of sorts- If I were the person in charge of ordering (still have a few years left of school) I can't see this as being a great product. FD is placing a lot of the cost of drug testing on the client (or at least it seems that way). They made minor alterations to the adjuvent of the formulation but the drug is essentially the same.
It is used in Australia with significantly less bad press than it had in the states. I'd be inclined to sit back and wait a few years and see what happens. But after reading a bit about what happened to the FDA vet who first revealed there may be a problem with PH6, I'm also inclined to read a bit more and become a more informed consumer before picking suppliers once I get into practice. My boss is going to love it!
# Posted By Alli | 6/16/08 7:33 PM
hi,
I would like to invite you to visit my website www.antheros.com.
We have the best pet urine & stain remover ever: LolliPet.
And guess what?
It is ORGANIC.
Thanks,
Bella
# Posted By bella w | 6/16/08 8:02 PM
I wouldn't use Prohart 6 and will not recommend it to my adoptors.

Frankly, there is a much better solution for preventing HW disease - which would be to make monthly hw pills available over the counter. The precaution of testing dogs for hw before using monthly preventive has pretty much been proven unnecessary, I believe. In fact, some vets now treat hw positive dogs with HeartGard or a generic formula. And the dosage in these monthly pills is so minor that most collies can even tolerate it - and a label warning about sensitive breeds would solve that problem.

I've been told that monthly hw pills are available over the counter in other countries.

I think a lot more people would use the monthly preventive if they could get it OTC without having to pay for a vet visit.
# Posted By Mary | 6/17/08 1:12 PM
let's make a comparison:

10kg dog (22lbs)
Heartgard at 6 monthly doses of 68mcg ivermectin would be 408mcg total ivermectin
Proheart injection at rec dose of 0.5ml would be 1700mcg moxidectin

Moxidectin is reportedly more active due to it's pharmcokinetics:
http://www.ncbi.nlm.nih.gov/pubmed/17847063?ordina...

Then again, the injection vehicle has some interesting compounds. Perhaps
this is responsible for a lot of the allergic type reactions, where none of the
typical avermectin overdosage symptoms are experienced.

It would be interesting to know, because moxidectin has potential for the treatment
and prevention of mites.
# Posted By eli | 6/19/08 12:23 AM
Heartworm preventative for a large dog costs at least 50% more than for a
small dog, yet the production expense for the pharmaceutical company is only
increased by a few cents.

Why? Pharmaceutical companies have done their market research. They know
that large dog owners are usually willing to pay more, and vets expect to make a
little more off a large dog client. It's kind of ridiculous, but it works.

As a matter of fact, the preventatives could be priced at three or four dollars
for a years supply and still be profitable, but they aren't. Covering less animals
maximizes profit. That is not necessarily a bad thing.
# Posted By eli | 6/19/08 1:06 AM
eli: Good point on the price of doses. That's true for Heartgard and Interceptor but some drugs have less steep pricepoints, sizewise (Revolution, for example). Revolution makes up for it by charging a zillion for the kitty doses (which is nonetheless still less than the dose-per-dose price of Advantage or Frontline). I KNOW you're right on their strategic marketing approach. Revolution is most popular in cats, that's their leading parisiticide, in fact. The dogs are just gravy, since other HW preventatives have consistently outperformed them. Hence the pricepoint/size skew. In the case of Heartgard, et al, dogs are their bread and butter. Again, therein lies the strategy for pricing.

Honestly, I see nothing nefarious about this. If I ran a drug company I'd do the same. It's not dishonest or unfair. Neither is it dishonest or unfair for me to buy the big dog sizes of the flea drugs and split the doses to keep my outdoor strays flea-free.

As far as profitability goes, i'm not sure that the Heartgard brand would be profitable if the product was priced as you suggest. Too much has gone into their marketing over the years. Sure, they've got a cash cow on ther hands and it's true they might save more dogs if they priced the product more affordably, but IMHO, they've earned their right to do so by leading the market so far in advance of their competitors.
# Posted By Dr. Patty Khuly | 6/20/08 9:02 AM
I do the same with my Frontline. Two extra-large doses can be split to provide flea protection to my 2 large dogs and 3 cats. But most vets don't tell you this unless you specifically ask about it.
# Posted By Shellie | 6/20/08 11:24 AM
Dr. Khuly,
You are right. The profitability of the market seems to keep the companies
on their feet with newer and better products. In the long run, this means
we get more safety and efficacy per dollar spent. Had the profitability not
been there, we might be stuck with narrower spectrum products. In which
case you just end up buying more products and/or tests to cover the bases.
# Posted By eli | 6/21/08 4:19 AM
Speaking of Revolution, are than any other options for heartworm preventative in cats? Also, how prevalent is heartworm in cats? When I talked to my vet about preventative for my cat last year he said he'd never heard of a feline heartworm case locally (WV). He generally doesn't recommend a preventative for cats because the infection is less prevalent in cats and its a low risk region even for dogs (true). However when I asked to have my cat tested for heartworm with his other labs they had to send it out and acted like it was a weird request. If they test that infrequently how would they know the prevalence? Of course about six months ago another vet in the area sent out "What you don't know could hurt your cat" postcards promoting Revolution. I've read lots of great articles/studies about heartworm in dogs but haven't found much info for cats.
Thanks!
# Posted By Shannon Watts | 6/22/08 7:04 PM
S M T W T F S
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
VIRTUAL VET HOSPITAL
Got a sick pet? Visit our Virtual Vet Hospital and admit your own pets as patients in Dolittler's unique pet healthcare forum.
PODCASTS
New! Download our latest podcasts:
ARCHIVES
FAVORITE POSTS
RECOMMENDED
CAREERISTS
Did you always want to be a vet or vet technician? Thinking about it? Working on it? Need some Help?
VetInfo.com
AVMA
Miami Vet Specialist
Penn Vet School
DVM.com
VIN
Vet News Network
Vet Practice News
Vetstoria
"The greatness of a nation can be judged by the way its animals are treated."
- Mohandas Gandhi
This blog is running version 5.003.