# Heartguard Question- How often?



## Maya's Mom (Apr 13, 2009)

I think I read on here that Heartguard can be given less often than every month, but I don't remember how often for sure. Was it every 45 days? 35 days? What is the source of information for learning that it can be given less frequently? Have lots of people heard this? I don't want to give it every month if it is not necessary , but want to make sure that it really is safe to give it less frequently. It doesn't make any sense to me to put chemicals in Maya's body more frequently than needed, but I definitely want to make sure she is protected from heartworm.


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## Doodle (Apr 6, 2009)

I've never heard of this and we've been using it for 13 years. What I was told by our vet is that, if you live in a cold winter environment, you can potentially skip the coldest winter months as long as you don't have warm days mixed in. We've always given it once a month year round because even in our coldest months there are some milder days on occasion.


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## IowaGold (Nov 3, 2009)

You can give it safely every 6 weeks. This is based on the lifecycle of the heartworm. Ivermectin (the medicine in Heartgard) kills 2 stages of immature heartworm (L3 and L4). L3 is the larvae that the mosquito injects into the dog when it takes it's blood meal. L4 is obviously the next stage in the maturation process. The fastest that a larvae can go from L3 thru L4 into L5 (which ivermectin does NOT kill) is around 60 days. So Heartgard actually acts "backwards" from the date of administration-killing any larvae that the dog was infected with in the last 6-8 weeks. There is no residual activity (the drug clears the body with in a couple of days, it does not stay in the body continuing to kill for 30 days). The 6 week interval of giving Heartgard allows for any leaway, either in the maturation process or the medicating process.


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## Loisiana (Jul 29, 2009)

I'm on a six week schedule.


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## Maya's Mom (Apr 13, 2009)

IowaGold said:


> You can give it safely every 6 weeks. This is based on the lifecycle of the heartworm. Ivermectin (the medicine in Heartgard) kills 2 stages of immature heartworm (L3 and L4). L3 is the larvae that the mosquito injects into the dog when it takes it's blood meal. L4 is obviously the next stage in the maturation process. The fastest that a larvae can go from L3 thru L4 into L5 (which ivermectin does NOT kill) is around 60 days. So Heartgard actually acts "backwards" from the date of administration-killing any larvae that the dog was infected with in the last 6-8 weeks. There is no residual activity (the drug clears the body with in a couple of days, it does not stay in the body continuing to kill for 30 days). The 6 week interval of giving Heartgard allows for any leaway, either in the maturation process or the medicating process.


Thanks so much. This is great info.  I think I will go with a 6 week schedule.


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## Penny & Maggie's Mom (Oct 4, 2007)

I've been on a 5 week schedule. It does cut down on the amount of chemical they ingest ( about 2 doses/year) and still gives me a week's leeway if I forget for some reason. The monthly dose schedule is for consumer ease of remembering.


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## Taz Monkey (Feb 25, 2007)

I give every 45 days. I set an alert on my iphone to remind me, which has been great!


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## C's Mom (Dec 7, 2009)

Has anyone seen this:
http://terriermandotcom.blogspot.com/2008/05/billion-dollar-heartworm-scam.html

I'd appreciate your thoughts/opinions.


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## fostermom (Sep 6, 2007)

I am going to talk to my vet about going to the 45 days dosing. With three large dogs, that would save me some money, that's for sure. She is a little old school, but she is a pretty good vet, so I hope she is up to date on this issue. 

C's Mom, I don't know what to think. I disagree with parts of that article. In NC, HW is very prevalent. I would hazard a guess that 70% of the adult dogs we get in are HW+. I think when the writer of the article mentioned that a few thousand dogs were tested and only 18 came up positive (in CA) he missed a variable. People who do not give HW preventative (or HW killer as he calls it) are not going to have their dogs tested for HW the majority of the time.


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## msdogs1976 (Dec 21, 2007)

Penny & Maggie's Mom said:


> The monthly dose schedule is for consumer ease of remembering.


For people like me.:yes:


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## Goldilocks (Jun 3, 2007)

Here in Ontario we only need to give heartworm treatment though the spring, summer and fall (the mosquito season). For the past two years I believe I have done a 40 day schedule. Last year Pippa saw a holistic vet as I was very curious about different things I had heard about heartworm preventative. She spent a long time talking to me and one of the things she said was that the medication has a farther reach back than 30 days.


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## IowaGold (Nov 3, 2009)

C's Mom said:


> Has anyone seen this:
> http://terriermandotcom.blogspot.com/2008/05/billion-dollar-heartworm-scam.html
> 
> I'd appreciate your thoughts/opinions.


I'll take the points as they are made in that "article":

#1 Heartworm disease is a real disease. Obviously in some parts of the country it is worse than others. But no where is truly "safe" anymore do to our travel habits. If one wants to gamble with a dangerous disease, fine, but MY dogs will get their prevention.

#2 Wrong. It takes 5-6 months for the microfilaria to go from L3 to adult, but ivermectin is only really active against stages L3 and L4 (so an infection can go from susceptible to ivermectin to not susceptible in less than 2 months). There may be a little activity against older microfilaria but not close to the 100% kill we need.

#3 True-for heartworm prevention. Most heartworm tablets also prevent some types of intestinal parasites, so have benefit as a year round prevention. Also in many, many areas of the country the safe "window" for heartworm is relatively short. For many people it is easier to remember to give a pill year round than to remember to get to the vet for a heartworm test and start the pills every spring. Whether or not to give preventive year round is a decision for each individual owner and his/her veterinarian.

#4 Infection with microfilaria is NOT heartworm disease. Heartworm disease is infection with adult heartworm. Preventives PREVENT microfilaria from developing into adults.

#5 I'm sure in this author's eyes, all medicines are toxins. As medicines there will always be individuals who can not take them, but for the general populace, the medicines in heartworm preventives are safe.

#6 Humans can be infected with heartworm microfilaria. They do not complete their lifecycle, but can cause lung damage/disease in the process of migration or after death from inflammation.

#7 It is true that there are dogs in some breeds that are overly sensitive to larger doses of ivermectin. There is a genetic test to determine if an individual dog is affected. And the amount of ivermectin in heartgard has been proven safe, even in affected individuals.

#8 I don't have a heartworm infected heart in my office. I can't speak for other veterinarians, but I do not use this "tactic" to generate business. I have seen several heartworm positive dogs in the eight years I have been a veterinarian and I live in Iowa, not the deep south where heartworm is even more common.

#9a Yes you can ask your vet for a script for Heartgard. Purchasing this prescription from a source other than your veterinarian voids the "Heartgard Guarantee" (which pays for diagnosis and treatment of heartworms and certain intestinal parasites).

#9b You *can* split the pills, but the ivermectin is not evenly distribuated thru out the chew, so you risk underdosing (more dangerous) and overdosing (less dangerous) the dogs that get the split pill. Also you must use the pill soon after opening the blister pack as ivermectin becomes less active the longer it is exposed to air (so you can't save half of it for next month).

#9c See post 3 of this thread.

#9c Ivermectin is ivermectin. Heartgard is not the only ivermectin product available. It is very hard to measure the minute quantities to match the dosages in Heartgard, so when giving other forms of ivermectin, it is typically given at quite a bit higher dosages. Giving ivermectin in this way would not be recommended for ivermectin-sensitive breeds, unless the individual dogs have be tested for the genetic mutation.

#10 Heartgard is usually safe to give to a heartworm infected dog. It could cause a massive die off of the microfilaria produced by the adult heartworms that could cause issues with inflammation, etc. in the dog, but this is very unlikely. A yearly heartworm test (recommended by the American Heartworm Society) is so that IF your dog were to have become infected with heartworm disease (remember that no medicine is ever 100%), that the disease would be in it's earlier stages and have caused little lasting damage to your dog. Early treatment gives your dog the best chance of a full recovery.

#11 Ideal treatment for heartworm disease is both expensive and scary. Giving doxycycline is recommended no matter which treat you choose. Yes, eventually heartworms will die and giving Heartgard will weaken them. But this slow kill method is SLOW. It will take up to 2 years to be heartworm free. During this time, the adult heartworms are continuing to cause damage in your dog's lungs. And to keep the damage at a minimum, you MUST keep the dog on strict cage rest the entire time of treatment. Who wants to do that for 2 years, vs. the 2 months with regular heartworm treatment.


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## IowaGold (Nov 3, 2009)

Another thought...if #2 were true (you only need to give 1 dose every 6 months), why would he ins #9c say that "if you gave 1/2 pill every *3 months*"?


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## CarolinaCasey (Jun 1, 2007)

Great response, Sarah. I learned a lot more from your post. To me, it isn't worth the risk to not give HG year round. Once you've seen a HW + dog, you don't want it to be your pet. I also want my guarantee from Merial if my dog should happen to get HW, so I'll buy it from my vet. That is the real saving! Not saving $5-10 for a years supply from an online retailer!


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## C's Mom (Dec 7, 2009)

Thank you Sarah for replying to the link above, I really appreciate it. 

I'm going to book an appointment for C to have his heartworm med in the spring and he will take it spring/summer/fall.


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## cham (Feb 21, 2008)

My 3 get their Heartgard year round, because of the addition protection the ivermectin, provides against some of the other parasites they could pick up from other dogs at daycare or at the dogpark. The K-9 Advantix they don't when there is snow on the ground or the ground is good and frozen. Once it thaws then the treatments start up again.


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## Willow52 (Aug 14, 2009)

Maggie was on Interceptor year round, Hank now is on TriHeart Plus year round. I had a dog in the 80's get heartworms (we lived in SC then). This was before much was known about it and she was not on preventative. Neither the treatment or the recovery was much fun. She did survive and lived to be 12 y.o.

The neighbor's dog was treated for heartworms last year so that's one case close to home (SW Ohio). I talked to the vet at Hank's first visit about preventative. It's just not something I feel I want to be second-guessing my vet about.


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## Florabora22 (Nov 30, 2008)

Loisiana said:


> I'm on a six week schedule.


Good to know. I was hoping I could stretch out Flora's dosage like I normally do back home, but wasn't sure if I should worry more about it in Louisiana.


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## marleysmummy (Jul 11, 2008)

This is interesting, I was told by my vet that NEVER EVER could I be late even 1 day with Marleys heartworm, she told me this around 10 times, basically drumming it into me.

I also has a friend who told me she was giving her dog too low a dosage of Ivermectin (she was dosing for a dog up 100lbs but her dog was 110 -115) and her dog still ended up with heartworm, although a much less severe case.


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## IowaGold (Nov 3, 2009)

Marleys mummy said:


> This is interesting, I was told by my vet that NEVER EVER could I be late even 1 day with Marleys heartworm, she told me this around 10 times, basically drumming it into me.
> 
> I also has a friend who told me she was giving her dog too low a dosage of Ivermectin (she was dosing for a dog up 100lbs but her dog was 110 -115) and her dog still ended up with heartworm, although a much less severe case.


Good gosh if you can't be late by even one day, I'm screwed! I'm the darn doctor and I'm often late by SEVERAL days. That's why I do it on a 30 day schedule. Surely I'll remember by the middle of the month!

Yep, the dose of ivermectin in the Heartgard is figured out pretty closely. I wouldn't trust my dogs to any dose lower than what is recommended.


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## Maya's Mom (Apr 13, 2009)

IowaGold said:


> I'll take the points as they are made in that "article":
> 
> #1 Heartworm disease is a real disease. Obviously in some parts of the country it is worse than others. But no where is truly "safe" anymore do to our travel habits. If one wants to gamble with a dangerous disease, fine, but MY dogs will get their prevention.
> 
> ...


This is such helpful information. Thanks for taking the time to explain it all. 

One last question is, do you have to give Heartgard every month year round to get the Heartgard guarantee? Or does giving it every 6 weeks void the guarantee?


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## IowaGold (Nov 3, 2009)

You do not need to give it year round. For heartworm disease I don't know if they have specific months it needs to be given based on state or if they support what ever schedule the vet recommends (as long as it's reasonable). I kind of doubt the 6 week schedule would be fully guaranteed, but I don't know for sure. There should be a telephone number on the box of Heartgard. They might be able to answer your questions. I'll try to remember to e-mail our HG rep and ask her exactly how the Heartgard guarantee is set up for heartworm disease. I imagine your vet would have to provide the reciept/proof that you purchased X number of pills, when you purchased those pills, what time of the month you give the meds, when your last heartworm test was (I suspect they would need to see two negative tests at least 6 months apart because of the way the lifecycle works). I'll try to remember to e-mail our HG rep and ask her exactly how the Heartgard guarantee is set up for heartworm disease.

FYI, for a description of how the Heartgard guarantee works for intestinal parasites see the thread titled something like "Iverheart vs. Heartgard Guarantee" (I think it was in the health section of the forum).


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