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IMHA - Looking for Answers
IMHA after vaccination in Brittany
Known causes of Immune Mediated Hemolytic Anemia - IMHA
Immune mediated hemolytic anemia
IMHA in Lab
IMHA
IMHA in Poodle
IMHA-Heartgard side effect
Heartgard and IMHA
also see Immune mediated hemolytic anemia
also see Thrombocytopenia
also see Blood Disorders
also see blood parasites
The Basenji, West Highland White terrier, English Springer Spaniel, Alaskan malamute,
poodle and beagle breeds can be congenitally predisposed to this condition due to defects
in enzymes (such as pyruvate kinase) or in the red blood cells.Heartgard (Rx) and Interceptor (Rx) both come under a lot of scrutiny as potential causes
of immune mediated hemolytic anemia (IMHA) and immune mediated thrombocytopenia (ITP)
because they are often the only medications that a pet is on when these occur. There is no
evidence at this time of an increase in the cases of IMHA or ITP in dogs on these preventatives.
IMHA after vaccination in Brittany
Question: I am a new subscriber to your service.
My 11 1/2 year old Brittany came down with IMHA ten days after her
DHLPC+Parvo vaccination. It has been going on for 14 days now .In be
beginning her PCV levels were 20,9 and went down to 10. She was given
Oxyglobin 3 times, and she is on 60mg of Prednison, 1.8ml of
Cyclosporum, 25 mg of Carafate twice a day. She was also on Azathioprine
25 mg, but we have now taken her off that. Her PCV has raisen to 22 and
been steady, but we do not seem to get any higher.
I was told to try Transfer Factors on her. Do you know anything about
them.?
Anything else we could do?
I really would appreciate some info ASAP.
Many thanks, Tia
Answer: Tia-
The February 15, 2001 issue of the AVMA Journal, which I received today,
has an article reviewing the use of medications for immune mediated
hemolytic anemia (IMHA). The authors are Sophie Grundy and Claudia Barton.I read this and the medications that are mentioned are prednisone,
dexamethasone, azathioprine (Imuran Rx), danazol, cyclosporine (Sandimune
Rx), cyclophosphamide, bovine hemoglobin (Oxyglobin Rx) and human
immunoglobulin (currently unavailable, I think).Of these medications, only cyclophosphamide and bovine hemoglobin appeared
to cause an increase in mortality. I was very surprised by the inclusion of
Oxyglobin in this short list, because I would have guessed it would be
beneficial.To the best of my ability to interpret the results of this study, there did
not appear to be any major impact on survival using multiple medications
over using prednisone alone.Among veterinarians who commonly treat IMHA, I am pretty sure that the
preference of most vets would be 1) dexamethasone or prednisone in the very
early treatment, almost always switching to prednisone alone quickly 2)
azathioprine as the most commonly used secondary medication. There wasn't a
statistical benefit in using this medication in survival times but it may
help to reduce side effects from steroids 3) cyclosporin is the newest
medication being used for IMHA and some vets like it a lot. It works better
and is safer if the dosage is adjusted based on serum levels, with 500ng/ml
being the lowest dosage thought to be effective and 1000ng/ml about the
level at which immunosuppression becomes severe enough to be a problem. I
think a lot of vets would use the human immunoglobulin if it were available
and/or less expensive.I could not find any information on "transfer factors", so I am not sure
what this references. It is possible that this could be a reference to
using fresh frozen plasma or cryoprecipitate to get blood clotting factors
but that is usually an emergency recommendation for use when the hemocrit
(PCV) is very low or when platelets are also low or not functioning properly.It is extremely important to continue to look for an underlying cause for
IMHA, especially in older patients, since it can be associated with certain
forms of cancer (hemangiosarcoma and other malignant cancers) and can occur
due to drug and toxin exposure. It is more common in the month after
vaccination, too.I usually stick to prednisone and I wouldn't be too upset by the progress
you have seen so far -- but I would still want to keep looking for an
underlying problem. Some dogs take longer to recover than others. We have
had to treat with prednisone for several months on a daily basis in some
dogs. We do use azathioprine occasionally, especially if dogs seem to be
having trouble with daily prednisone.I wish that I did have a really good suggestion for a medication that would
be reliably better than the others.Mike Richards, DVM
2/15/2001
Known causes of immune mediated hemolytic anemia (IMHA)
Question: Dear Dr. Richards,
I am a subscriber to your service. I have a question about immune
mediated hemolytic anemia, IMHA.
On November 8, 2000, my six year old female schnauzer, Indy Anna, died
from IMHA. Three days prior, she was healthy and we walked our normal 2 1/2
miles. She was my closest buddy, and I am grieved by her loss.
I read quite a bit of exchange on this server about this disease. I
realize that there is not a clear cause and effect relationship in regard to
it. Yet, I would like to know all the possible causes of this horrible
disease. I have talked to my local vet and to the vets at Purdue University,
who tried valiantly to save my dog. My question is: what caused Indy to get
IMHA? Is there some predilection to this disease in schnauzers? Is there
something I did that brought on this disease? Could I have saved her? Did my
local vet act wisely?
Here is some information to assist your answer. Over the summer, Indy
showed a high level of Alkaline Phosphate in her complete blood test. We did
a low-dose DEX test, an ACTH test, a liver x-ray, and a liver sonagram to
determine cause, possibly Cushings Disease. Nothing was found. Results were
sent to Purdue University for consultation. Advice: liver is a bit
discolored, retest in 4 months (December). Indy had pancreatitis for two
years. It was under control with Canine ID food. According to blood tests at
the time of her illness, she was not suffering from either Pancreatitis or
Cushings.
Indy took Sentinel monthly. We used Frontline Advantage for 3 months
over the summer. She took a glyco-nutrient daily. She had not had Sentinel
for a month prior to onset of IMHA. She had not had vaccinations for almost a
year. She was slightly overweight, 19 pounds. We fought weight her entire
life. She was very athletic, having walked long distances daily.
Indy became ill during the night on Sunday, Nov.5th. She vomited
twice. On Monday morning, she collapsed, breathing hard. I took her to the
vet immediately. On the table, Indy's head hung way down. The vet gave her
IV fluids (under her skin), an antibiotic shot, and took blood (the
bloodwork was not done STAT). She sent her home. By 6:00 pm, Indy was
weaker. I took her back to the vet. She was hospitalized locally overnight.
The vet thought she was in shock and started treatment, I think with
steroids. At 7:00 am. I received a call that she was doing well. At 8:00 am,
the blood tests were back and showed IMHA. The vet did steroid treatment. I
arrived at 8:30 to check on Indy. I was told we might lose her. Imagine my
shock and dismay! My husband rushed to Bloomington, IN from Indianapolis
(where he works) and we took Indy to Purdue's small animal hospital,
emergency care. Her hemoglobin was at 8.
Indy rejected three transfusions. We then gave her oxyglobin and
plasma. She had massive steroids. She stablized a bit. I went home to get a
car and pack a bag for an extended stay. Then, in the very early morning,
she went down, probably from a bloodclot to her lungs. The vets knew I was
on the highway and 1 1/2 hours away from the clinic, and they worked to save
her. They put her on a respirator and massaged her heart externally. They
brought her back five times. I arrived and was able to talk to Indy, when
her heart stopped a sixth time, I let her go.
Thank you for your response to this note. You can publish it if you
like.
Sincerely, LynneAnswer: Lynne-
These are the known causes of immune mediated hemolytic anemia (IMHA) that
I know of:Genetic predisposition to this condition is known to occur in the following
breeds:
American cocker spaniels (most common breed to develop IMHA)
English Springer Spaniel
Old English sheepdog
Irish setter
Poodle
Dachshund
(list from "Textbook of Internal Medicine, 5th Ed., Ettinger and Feldman)Drugs that might induce IMHA:
sulfonamides
cephalosporins
penicillins
methimazole
procainamideA higher incidence of IMHA is seen in dogs within a month of vaccinations
so it is presumed at the present time that some dogs react to vaccination
by developing IMHA.Metastatic cancer, especially hemangiosarcoma, is a common cause of IMHA in
older dogs.Tick borne illnesses, usually ehrlichiosis but possibly Rocky Mountain
spotted fever and Lyme disease can lead to IMHA.Severe bacterial infections (sepsis, for example) and some viral illnesses
(more common in cats) can lead to IMHA.Most cases of immune mediated hemolytic anemia are still unexplained
(idiopathic) at this time. Hopefully, it will be possible to identify more
and more causes of this condition as time goes on and perhaps someday to be
able to definitively identify a cause in individual patients for which an
obvious cause, such as metastatic cancer, is not present.We have seen two cases of IMHA in schnauzers secondary to hemangiosarcoma.
In both of these cases, the IMHA was recognized prior to recognition of the
cancer, despite the fact that one of the dogs was examined by a good
practice in the owner's home town, a good emergency veterinary clinic and
by our practice. In fact, in that particular patient, we had to do a
post-mortem examination to find the cancer. I am not sure if this is a
common occurrence in other practices, but it doesn't seem to be reported in
the literature, if it is.I can't imagine what more you could have done to save Indy Anna. You did
all the right things, seeking veterinary care early, making the decision to
go to a veterinary school, using oxyglobin when transfusion was not helping
and the care as things went along seems very appropriate. I often wish that
making the right decisions would guarantee the right outcome, but that just
isn't something that happens all the time in veterinary medicine. You did
well for Indy Anna and you should not worry that you did not do enough. It is
extraordinarily hard to lose a friend when there is no clear explanation of
what happened.Mike Richards, DVM
11/26/2000
Q: Dear Doctor Mike, My 7 year-old yellow lab is very sick and my family has pretty much accepted the fact that she is going to die very soon. I on the other hand, am having a very difficult time with this and need to make sure we have explored all of our options. We have taken bone marrow samples and determined she does not have cancer. They think she has Autoimmune Hemolytic Anemia and her red blood cell count has dropped to a fraction of normal levels. We have tried chemotherapy but she started having severe side effects so we decided to stop treatment. She is currently taking cortisone shots which seem to help her appetite but she is not getting any better. I have read that cyclophosphamide and prednisone have been effective in other cases and I wanted to know if you had any other suggestions. I'm very concerned that she could die at any time so if you could respond quickly it would mean a lot to me. Thanks in advance for your help. Sincerely, Geoffrey
A: Geoffrey-
Immune mediated hemolytic anemia (IMHA) can be very difficult to treat successfully. It is hard to distinguish from problems caused by hemangiosarcoma (a form of cancer) in dogs and our experience has been that Labs are more prone to this than most breeds. While seven years of age would be young for this cancer to occur we have seen it in Labradors and golden retrievers in this age range.
When standard therapy using corticosteroids and other immunosuppressive agents doesn't work it may be worthwhile to consider trying Danazole (Rx). This medication has been reported to be beneficial in some cases of IMHA. The June issue of the AVMA journal had an article on using human immunoglobulins for this but it was only helpful in some dogs. I have no idea how one acquires this product, though. I have not seen references to using cyclophosphamide for IMHA but have seen references to using this for immune mediated thrombocytopenia (loss of platelets). These are markedly different disease processes. We see ITP most commonly as a drug reaction and withdrawal of the offending drug, along with corticosteroids, works very well to stop the clinical signs in most dogs.
I hope that improvement did occur since you wrote.
Mike Richards, DVM
Q: Dr. Mike, I have a 10 year old Cocker Spaniel who has just fallen ill with Autoimmune
Hemolytic Anemia. I found my dog wavering and eventually collapsing. I took him to my vet
who checked his PCV. It registered 21 and eventually fell to 13. At that point the vet gave
him a blood transfusion along with steroids and Cytoxin. He has responded quite well. His
current PCV is 34 (two days after the transfusion. I am concerned however because the
doctor can find no underlying cause for this disease in my dog. Also, because my dog
responded so quickly, I almost feel that the doctors are uncertain now that this is actually
AIHA. My only suspicion if it is indeed AIHA is that I gave my dog a 30 day chewable
Heartguard two days prior to his collapse. Could this be a factor? Also, I am quite concerned
about his future. If a dog is diagnosed with this disease, but no cause for the disease is found,
what is his chance of recovery without coming down with the disease again? I'm worried,
because he stays home by himself all day while I work and I can't monitor his condition.
Do you have any advice? Thanks! BrianA: Brian- I am almost afraid to answer your question as I have been in a long email discussion
over this issue recently. I believe that in any individual dog, almost any medication can have
almost any side effect. Therefore, I have to say that I think Heartgard (Rx) could potentially
cause immune mediated hemolytic anemia (IMHA). BUT -- I think it is not very likely. I get
this exact question relating to all of the medications used on a consistent basis -- Heartgard
(Rx), Interceptor (Rx), Frontline (Rx), Advantage (Rx), Program (Rx) and probably others
I can't remember offhand. All of these are recently developed medications and we saw IMHA
in our practice many times prior to their development.To judge if these medications are having an effect, in general, it is necessary to compare the
expected rate of IMHA in the population to the rate of IMHA in the population when one of
these products is being used. All of the companies currently claim that the rate of IMHA is no
greater when their products are used than when they are not. I have no way of being sure of this
but these are reputable pharmaceutical companies and I have no reason to doubt their word at
the present time.To judge if one of these products is causing IMHA in an individual may be impossible and is at
least very difficult if the product is not used again. Many clients opt not to try further use of a
product they think might have caused IMHA since there are alternative medications for each
of the products most frequently suspected. In some instances death of the pet precludes this sort
of decision and leaves pet owners very confused and sometimes angry. This is especially frustrating
since there is no way I know of to prove or disprove the theory that the IMHA was induced by
a product after the death of the pet. If you want to, you can administer Heartgard in the future
and if there is no recurrence of the IHMA it would be less likely to have induced this problem.
I think I would be comfortable doing that in the case of Heartgard but if you are not, just
change medications for heartworm prevention since others are available.IMHA can recur but often it does not. I hope it will not for your dog.
I hope this helps and does not just muddy the water more for you.
Mike Richards, DVM
Q: dr. mike today i learned that my poodle, pierre, who is six may have this disorder.
he is epileptic and has taken phenobarb since he was 4 months old, could this have
brought it on. my vet will consult with me again in a few hours but thought i would get
another opinion on this. my family is devastated! three days ago pierre was fine. what
to do now? what are his chances? any comments would be greatly appreciated. D'AnnA: D'Ann-
Several medications can lead to problems with immune mediated hemolytic anemia (IMHA)
and phenobarbital is one of them. This is not a very common effect, though. Poodles are
predisposed to IMHA and it is harder in them to sort through possible causes, since the
condition occurs for no apparent reason in poodles more frequently than in most dog breeds.
The success rate in treating this condition varies widely. It is usually not a good idea to
abruptly stop giving phenobarbital, especially in an epileptic patient. This can make therapy
a little more difficult if it is part of the problem but usually drug induced IMHA is easier to
treat than "naturally occurring" IMHA, so that helps. I am hoping Pierre is doing much
better now.Mike Richards, DVM
Q: My toy poodle Buttons was fine until recently when we started her on her
heartworm medication, the one month chewable variety. The next day she became
very lethargic and weak almost to the point of not being able to stand. I rushed her
to the vet early this morning and they diagnosed her with a very low red blood cell
count something like 14 instead of the normal 35. Her temperature was normal at
102, according to the vet. She was put on a large dose of steroids at 10:30 AM
and this evening the vet called and said she had gained her red blood cell count
very slightly. He seems to think she may be out of danger, but I'm still very concerned.
I also came across something on the web referring to "shunts" in pets, namely small
dogs such as toy poodles. The vet has no idea what may have caused The
medication is Heartgard Plus by Merck which contains ivermectin/pyrantel.
Could you please give me your opinion on this and any further recommended treatment?
Also, does this sound curable? Thanks, TomA: Tom- Liver shunts are a congenital problem in some dogs. During gestation the placenta
delivers blood with food and oxygen from the mother through the umbilical vein. This means
that in the fetus, circulation is the reverse of circulation after birth, because the fetus' veins have
the oxygenated blood and arteries return unoxygentated blood to the heart. In order to make
this work, there is a shunt from the liver venous circulation to the arterial circulation. At birth,
the pressure within the circulatory system changes as respiration occurs and this shuts the shunt,
which eventually disappears. If this reverse in circulation doesn't happen for some reason, the
liver is deprived of a blood supply and doesn't develop properly after birth. Many puppies can
live with the small functioning portion of the liver for some time but eventually have problems and
usually die if the situation is uncorrected. It is possible to surgically close the shunt and the surgery
works well. I can remember hearing of one sheltie that was 6 years of age (or possibly older)
before a congenital liver shunt was recognized, so some dogs can live a long time with this problem.
It is very unlikely that your poodle is experiencing problems from a liver shunt.Heartgard (Rx) and Interceptor (Rx) both come under a lot of scrutiny as potential
causes of immune medicated hemolytic anemia (IMHA) and immune mediated
thrombocytopenia (ITP) because they are often the only medications that a pet
is on when these occur. There is no evidence at this time of an increase in the
cases of IMHA or ITP in dogs on these preventatives. Recently, the once monthly
flea treatments have also been subjected to some suspicion since they are the newest
medications many dogs are on when these problems occur. There is also no evidence that
they cause either of these conditions, presently. That doesn't mean new information won't
come to light at some future time but I honestly do not suspect these medications as
culprits in these diseases.Mike Richards, DVM
Heartgard and Immune Mediated Hemolytic Anemia - continued
Q: Dr. Mike, I am writing you to let you know that all evidence now points to Heartgard
with Ivermectin as being the drug that triggered Immune mediated hemolytic anemia in
my toy poodle, which eventually died. Ivermectin is a potential killer, period. I would
appreciate you and others like you getting the word out that the big drug manufacturers
are poisoning our pets with chemicals like these. If I have to call and email every vet in
the US, I will. I will also go to every chat room and site where people go to get info
about pets on the internet, to let them know the dangers of Ivermectin, because I know
that Merck and the others will simply sweep it under the rug. TomA: Tom- If you were able to convince pet owners not to use ivermectin you would be
doing a grave disservice to a great number of pet owners. Heartworms kill many more
dogs than immune mediated hemolytic anemia ever will, even if ivermectin does trigger
this response in some dogs. There are analogous situations in many areas of life. Once
in a while, wearing a seatbelt will kill a motorist in an accident instead of saving their life.
Overall, though, seatbelts save lives. The family of a person who dies because of the
seatbelt feels cheated and wishes that their loved one was not wearing it. Their sentiments
are real and they can legitimately say that the seatbelt killed their relative. But it would still
be wrong to campaign against seatbelts.I know you hurt. I wish that I could encourage you in your actions. Please let me know what
information (evidence) you have that leads you to be so sure that ivermectin was the underlying
cause of the IMHA. I really do not know of a way to confirm this suspicion -- or to disprove it.Mike Richards, DVM
Immune mediated hemolytic anemia (IMHA)
Q: Dr Mike, Thanks for posting my original question on your site. Here is what happened over the past several days with my toy poodle which has been in perfect health for all her life, except for an occasional pinched nerve in her back that acts up. I had her blood tested for heartworms and got the ok to start her on heartgard which I did a little over a week ago. Two days later she started to lose her appetite. By the third day she was very lethargic and beginning to sway as if about to fall down. I rushed her to the vet and noticed her gums were almost gray. The vet immediately put her on steroids to stabilize her. Her red blood cell count was down to 14 from a normal 35 or so. She has been under 24 ICU for the last 3 days and is finally coming around after several transfusions, intravenous medications and whatever else you can think of. She was tested for everything under the sun and was found to have immune mediated hemalytic anemia which you mentioned in your first reply to me. All of the doctors involved asked is she had received any medication at all recently in the way of shots or whatever, which she hadn't...except for the Heartgard Plus 30 day chewable. My suspicions lie with this medication, but just about every one of the drs. are unwilling to point the finger at it. I found the test results of the drug when Merck first came out with it and some of the possible adverse side effects fit the pattern of what was happening to my dog. It almost seems as if nobody dares to pin possible dangerous side effects on this drug. I definitely am and intend to pursue it as far as possible, maybe even seeing if Merck will pay my nearly $2000. vet bills. I visited the dog tonight and it looks as though she's on the road back and with any luck I'll have her home in the next few days. Just wanted to give you an update because you're the only doctor out of the many I've conferred with in the last week (I even called Merck) who dares to place a possible connection here. Would like your further input on this if possible and what you think I could do further. Thanks again, Tom
A: Tom- It is always difficult for clients to understand immune mediated hemolytic anemia (IMHA) and immune mediated thrombocytopenia (ITP). People seem to naturally look for "cause and effect" relationships whenever problems occur. While there often is an underlying cause for these and other problems there often is not. The medications that are used on a frequent or fairly frequent basis often get blamed for lots of problems that are not due to them because of this need to find a cause for every effect. This is especially confusing in the case of IMHA and ITP because there are definite known inciting medications and therefore there is a strong tendency to look for a inciting cause among medications the pet is on.
The monthly heartworm preventatives have been very beneficial for our patients. They have drastically reduced the number of dogs we treat for heartworms each year. I can understand the reluctance of veterinarians to consider them as a possible cause of conditions such as this. Despite this, it is necessary to be realistic and accept that any medication can cause problems in a few individuals. Since these are extremely beneficial medications, that risk would be acceptable even if it were known to exist.
As I think I pointed out in the first letter, I am not aware of a relationship between ivermectin (Heartgard Rx) and immune mediated hemolytic anemia. Despite that, I think it has to be considered as a possible cause. I think it is important to notify Merck that this happened so that it is documented - in case the number of reported cases does start to exceed the number expected in the general population of dogs on Heartgard. The currently available information suggests that the expected number of cases of IMHA in the population of dogs taking monthly heartworm preventatives has not been exceeded -- making it unlikely that there is a cause and effect relationship between the IMHA and the ivermectin.
If you live in a heartworm endemic area, you need to use a heartworm preventative. Switching to milbemycin (Interceptor Rx) may relieve the worry of continued use of ivermectin (Heartgard Rx). It was good to report this to Merck. If there is a problem, eventually it will surface if people continue to do this. Until it is proven, though, I can see no reason to get angry with Merck. Continue to work with your vet to ensure that your dog keeps on improving. I know it is hard to accept that some things just happen -- but it seems to be the case.
Mike Richards, DVM
IMHA and Ivermec - continued - more cases
Q: Dear Dr. Richards, In response to your email regarding my toy poodle, ivermectin, and IMHA, I just want to say, that, you are right...I hurt, more than you can imagine. That little bundle of joy was such an important part of my life for 9 years, it would take me 9 years just to describe how much. The pain of losing her in such a way is truly horrible. It has been 4 weeks now and I still wake in the middle of the night thinking of what she went through. I have come across a number of breeders who will not even administer ivermectin to their dogs. In calling around to local vets, I have also have even found some who will not recommend it for certain breeds, because of their seeming susceptibility to adverse reactions. Cockers, collies, and poodles being among them. To answer you about doing an injustice to other dog owners, it sure sounds to me like you've done a bit of a 180 here from your first responses to my concerns about ivermectin, where you "believed" there could be a connection. Now you seem to be saying that there are SO many dogs on this drug, that a few adverse reactions should somehow be accepted! Boy, it sure sounds like the response I've been getting when I talk to the people at Merck. For the good of the cause...well, tell that to my precious little girl who, in my mind, should still be here with me as I write this. I know that drugs like Heartgard/ivermectin are HUGE money makers for Merck AND a the vets who carry the line. I certainly hope that it wouldn't cloud this whole issue of investigating this whole thing. And, besides, aren't there alternative heartworm medications such as Interceptor (recommended over Heartgard by many of the breeders I spoke to, by the way) and the daily dosage medications? I just don't understand your concern here. MY main contention is this: Apparently there are a number of breeds of dogs that are susceptible to things like IMHA, whether because of genetic predisposition's or whatever. Merck knows this as well as the veterinary community. I want to know why this is not in the information that comes with the drug? If I had even known there was a possibility of an adverse reaction in my dog, do you think I would have given it to her? I blame Merck for this first and my vet second. I have come across several people who have posted to a site on the internet referring to IMHA. Keep in mind, these are just a few who have access to the internet. I'd be willing to bet there are MANY more out there experiencing the same thing, but have no way to make it known, or don't even think to make the connection between ivermectin and IMHA.
Yet another Cocker Spaniel... "I have a 10 year old Cocker Spaniel named Casey. He is in amazingly good health for a 10 year old dog. However on June 19th, I noticed that he was swaying back and forth and ultimately collapsed. He did a similar thing on the 19th and I took him to the vet on the 20th. He was immediately diagnosed with AIHA and admitted to an Emergency Veterinary Hospital. His PCV was at 21 when admitted and dropped to 13. He was given a transfusion, cytoxin, and steroids and now three days later his PCV is up to 34 and stable. I can only hope that his health continues to improve. I feel pretty helpless. The doctors are unable to deduce what could have caused the onset of this, because there are no other existing factors that normally are seen with this disease (cancer, hemorrhaging, etc) but from reading your comments I am suspicious of a possible factor. The ONLY medication given to Casey was Heartgard 30 Day Chewables on June 17th. I have to think there is some correlation, especially since so many others have had the same experience. My thoughts and prayers are with the rest of you going through this horrible ordeal." Brian
"My sympathies to all of you who lost your dogs. I nearly lost mine, and am still dealing with her recovery. First, I think the possible connection of heartworm medication and AIHA is worth looking into. But don't look to mainstream vets for much support. Merck has a clever legal staff whose main line of defense would probably be that the autoimmune disorder exacerbated the effects of the medication. Look into it anyway."
"I'm just stunned. My dog, a precious springer spaniel, 4 1/2 year old female, was diagnosed with IMHA 2 days ago. She is hospitalized and being treated in a similar manner as I've read here. The thought of losing her is devastating, but as a nurse, I understand. The amazing thing is that Heartguard also crossed my mind as the vets were quizzing me about her, habits, drugs. She has taken it in 3 previous years without problem, she has had 2 doses of the 6 for this year. I will share these notes with my vet, also please keep me informed about more info discovered and other cases. In the other cases involving Heartguard, had the dog had the drug in previous years, did the hemolytic anemia develop after the first dose. As I'm hoping and praying for my dog's recovery, I wish others the best and my condolences to those of you who have lost your friends." Kathy
"Two years ago, my perfectly healthy black lab got violently ill 2 days after giving it Heartgard. It was the only medication I had given the dog in the previous weeks. It had severe vomiting and diarrahea. After a few days, it couldn't even walk...it died within a week. My suspicions went immediately to the Heartgard, but upon asking my husband his opinion, he basically said there was no way, so I forgot about the whole thing and never thought anything else about it." (Isn't one of the most common adverse reactions to ivermectin is vomiting and diarrhea?) Grace
Tom, So very sorry that you lost your precious toy poodle, and I am sorry to be so slow in replying...I have been out of town for 2 1/2 weeks and had no access to internet. Ivermectin IS controversial. There is some suggestion, as noted by Dr. Jean Dodds in a seminar recently, that the large molecules in ivermectin and some of the other drugs given to dogs may initiate an autoimmune disease in those animals predisposed by hormonal states, heredity, or other environmental exposures. It has not yet been well established that ivermectin can cause hemolytic anemia, but it may possibly be a contributing factor. I hope that you are able to find another puppy ASAP to fill the large cavity left in your life by the departure of your little toy poodle. My sincere sympathy! Grace
In closing, Dr. Richards, I will not and can not let this drop. I KNOW in my heart that ivermectin triggered IMHA in my little girl. I KNOW she should still be here. I KNOW that Merck doesn't really care, and is willing to write off a few unfortunates like my Buttons, for the sake of the large profits. I also BELIEVE there is a lot more of this going on out there, that simply has not surfaced yet, but that in time, it will. Lastly, isn't it interesting that Merck is now using a photo of a Collie in it's promotional campaign for Heartgard. Of course we know that this is the dog MOST adversely affected by Ivermectin. What's THAT tell you about Merck? Very distraught and frustrated, Tom
A: Tom- I do think that there is a possible connection between the use of ivermectin and IMHA in your dog's case. As you continue to research this I think you will find the same connections made to most medications that are used on a routine basis, including milbemycin (Interceptor), vaccinations, seizure control medications, monthly flea control products and antibiotics. This is where the difficulty comes when discussing IMHA -- is the incidence of reactions in dogs on ivermectin higher than the the incidence of IMHA in the general population? I can not answer this question with much authority because these sorts of figures are very hard to come by in veterinary medicine in general -- we simply have no good central tracking method such as insurance companies or a "Center for Veterinary Disease Control" I think it is wrong to assume that ivermectin could not be the cause of the problem, though. I know this is confusing and not entirely satisfactory to you.
I know of no studies suggesting an increase in sensitivity to ivermectin in poodles or cocker spaniels. There is evidence that collies are more susceptible to ivermectin toxicity but the dose range necessary for toxicity is at least 16 times higher than the dosage necessary to control heartworms and because of this Heartgard (Rx), containing ivermectin, is approved for use in all dog breeds for the control of heartworms.
Since ivermectin is only present in the body in significant amounts for about 3 days after administration of a Heartgard tablet I was hoping that your dog would recover from the IMHA, as withdrawal of the offending medication in combination with therapy is often sufficient to stop the hemolytic anemia. Had this been the case I would have advocated using an alternative heartworm preventative in the future, in your dog's individual case. But I would not and can not advocate discontinuing the use of this medication in the majority of dogs as it has been extremely beneficial for a great number of dogs.
It took me several years to get over the loss of my high school and college buddy, a labrador retriever, who died during an anesthetic procedure. For a very long time I suspected carelessness or fault on the part of the vet who was working on her. After careful review of anesthetic related deaths that have occurred in my practice I know that this can happen even when all reasonable precautions have been taken. If I did not have the advantage of being able to see this situation from "the other side" I may never have understood or forgiven the vet involved in my dog's death. After reviewing the three cases in which I feel some or even strong responsibility for the death of pets in my care for anesthetic procedures I have had to struggle with forgiveness from a whole different aspect. In the end, we are all human and all that we can do is the best we can do at any given time. The bad thing is that isn't good enough in a profession such as mine. I am very grateful for the two owners who have forgiven me for the loss of their pets -- and let me know. I am still struggling with the owner of the third pet. When Hank died, I knew that there was going to be a lot of soul searching on both the owner's and the vet's part. You see, he was mine. I really do understand the pain of losing a pet because of a medical procedure. It has happened to me twice. Despite this, I continue to spay and neuter my pets and I continue to do surgery on them when it seems necessary. The overall benefits exceed the risk.
That is the whole point I am trying to make -- you may very well be right that ivermectin was the trigger for IMHA in your poodle but that doesn't mean that the medication's benefits do not outweigh its risks, overall. It is just so damned hard to be one of the persons who suffers due to the risk.
Mike Richards, DVM
Closure
Dr Richards, I just want to thank you for your very understanding letter regarding "Buttons", my toy poodle and the IMHA she contracted. I know how very busy you must be and I appreciate your taking the time to address my situation.
I intend to send a detailed letter to Merck and I want to build as much of a case as possible. Would you mind if I used any of the responses that you've sent to me over the past several weeks? I promise that I would not take them out of context...I'm not like that. I do want to come to closure with this though and get on with my life.
Just to let you know that I don't expect Merck to yank Heartgard from the market on my behalf, because I do realize how beneficial it is in preventing more of another problem from occurring. I do, however, expect some sort of disclaimer or warning on the packaging so people like myself can at least be aware of the POTENTIAL harm of Ivermectin in some dogs. Thanks again for listening, and responding, Tom
As an aside to my email...the FDA/CVM does monitor and register all the REPORTS that come in, under their adverse drug reaction category. Dr. Neal Bateller (sp.) told me that, unfortunately, many of these types of cases don't get reported for whatever reasons. I know that I have reported my situation and another fellow has reported his. They both now appear on their web site under a statistical column, for whatever good it does. Dr. Bateller also said that if enough of this kind of report came in, they would approach Merck about it. Again, for whatever good that would do. Tom
A: Tom-
I do not have any objection to your use of correspondence from me in discussions with Merck. I am pretty sure that they are aware of the website, anyway. Michal pointed out to me that I had not sent you one piece of information found in previous posts on IMHA. Poodles are one of the breeds considered to be susceptible to this problem as a naturally occurring phenomenon. This does not change any of the previous information, it just is one more thing to consider.
Mike Richards, DVM
Last edited 01/30/05