Proheart 6 was pulled from the market, although the manufacturers keep trying to have it re-approved. The problems were perhaps due to a malfunction of the time-release mechanism.

I haven't heard of another injectible heartworm preventative or one that is supposed to protect a dog for a year, but it might be a medication that is approved for use in Mexico and not here in the States.

Like you, after the pro-heart debacle, I'd be very leary of any long-term HW preventative until it had been on the market and used without widespread incidents of death or serious illness for a number of years.

My doglets get the ProHeart shot every 6 months. We haven't had any issues with it at all. Our Labrador, Molly, got heartworms while using the monthly HeartGuard. HeartGuard paid to have her treated. Our vet feels like ProHeart is the best altenative to the monthly treatments that are available. He hasn't seen any dogs with bad reactions in his practice, and we have no qualms about using it.

I have enclosed a link to the fda site with info on ProHeart 6. It is back on the market, and I can see where it has a niche to fill. That being said, I am more comfortable with monthly treatments for my dog for several reasons. Meds like these depend on the eficacy of slow release of the active ingredients. Once it is in the bloodstream, it is there for a looooooong time releasing the active ingredients....... and should your pet have an adverse reaction, he'll continue to have it for a loooong time as well. With monthly doses, one at least has an opportunity to deal with a dose who will be gone in a month. I am also very careful to administer the monthly med on time and also watch to be sure it stays ingested and not puked up, thereby leaving the dog with no protection. I have also read about meds where the encapsulation providing the slow release failed and the dosages were not controlled in the proper timeframe (although that has not been claimed with this product) Time release meds fill the niche for clients who cannot or will not be able to give doses in a timely manner. I give my dog heartworm preventatives each month anymore, instead of just 'mosquito active' months. I have found that regardless of how cold it gets outside, I have found mosquitoes every month of the year in the house. I'm assuming they have protection somewhere they can and do breed and not be totally killed off in winter. It just takes one bite from the wrong mosquito. If you are getting a six month medication, do not expect it to provide protection for a year.

Here is a link that might be useful: ProHeart 6

Wow.
Thanks for the info.
I was also glad to see, after so many years/deaths, that Canyon Creek has been pulled.
Thanks for the info.

I can't get myself to trust something like that. In my head, if you are not administering heartworm pills every month, you aren't keeping it in their system. Who is to say the vaccine won't wear off in their body before they are due for another. It's like the depo birth control injection. There have been untold amounts of women getting pregnant during the time it was supposed to still be in their system. (I know, I know. Birth control is way off topic, but this was the first similar situation I could think of as an example) It all comes down to how an individual's body functions. Same applies to animals. My German shepherd is on interceptor. It's cheaper than HeartGuard & covers more than just heartworms. Our vet kept insisting on using the 6 months shot, but I kept telling him no. He persisted to the point that I got agitated & couldn't hide my annoyance from him. He didn't like the fact I was putting my foot down. At our vet, the shot & 6 month supply of interceptor cost the same, give or take a few cents, so it wasn't like he was losing any money. Though he never said anything directly about my opposition, the faces he made & the fact that he didn't seem too keen on me having power over what happens to my pet, I don't think I'll be using him anymore if my dog has to make a trip to the vet. I'll only go there just to pick up another supply of heartworm pills.