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Dr. Drew
Dr. Drew, Dog Veterinarian
Category: Dog Veterinary
Satisfied Customers: 16846
Experience:  Small Animal Medicine and Surgery
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Gave my three dogs Trifexis yesterday, one vomited within 2

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Gave my three dogs Trifexis yesterday, one vomited within 2 hours, later began breathing heavy, and vomited clear bile. The other two were very lethargic. Took the first one to the emergency clinc, they kept him overnight, gave him fluids and steroids, they said he has heartworms and the medicine had made him sick. Took the other two to the vet this morning, he gave them antibotics and gave some for us to give them at home. All three are home and still breathing heavy and lethargic, have not eaten nor want anything to drink. Contacted the company, they don't think it is their medicine, they had the vet to draw more blood today. I don't know where I am with these dogs, the er vet doesn't agree with my regular vet and the vet with Trifexis only thinks this is a great study for them. My dogs are laying around, breathing heavy. Any ideas as to whats next - will this go away on its own, when?
Hi, thanks for your question. Were your dogs tested for heartworm by your regular vet, before the Trifexis was prescribed?
Customer: replied 6 years ago.
OK, thanks. In that case, that would certainly send up a "red flag" to me, that this reaction could be the result of baby heartworms dying in the bloodstream, after the Trifexis was administered. This can create a serious allergic (anaphylactic) reaction, which can cause vomiting and shock and collapse. Now, some dogs who receive Trifexis may vomit, just due to stomach irritation, but the effect is milder than what you've described, and typically does not require treatment.

Your regular vet may disagree with the thoughts of the ER vet, but if your regular vet didn't test for heartworm disease before prescribing the Trifexis, then that's really not following the proper procedure. If the ER vet tested for heartworm, and found a positive result, then that's the most likely explanation until proven otherwise.
Customer: replied 6 years ago.
My question is really - What now? how long does this go on? What can I expect for my dogs from here on? What can I do to make this better?
Well, if the problem truly was caused by the use of a heartworm preventative in heartworm-positive dog(s), then the treatment revolves around suppressing the severe inflammatory response to dying worms, usually with the use of corticosteroids, intravenous fluids, and strict cage rest. This may need to be continued for several days or more, depending on their progress. Most dogs will recover from this sort of problem, with proper supportive care as needed. However, there is also a chance of liver problems, so it is important to have some bloodwork rechecked as the days go on.
Customer: replied 6 years ago.
They are not eating and only drinking small amounts (with lots of encouragement). Just gave the one that was in the ER last night - Doxycycl (100 mg), within about 30 minutes he vomited this up, and almost appeared to have a seizure, as he stiffened and fell over as he vomited - he is now lying very still, breathing is not heavy like it was last night - one of the others is breathing very hard, she did eat earlier, but not drinking. Is the reaction of the vomiting, due to an empty stomach? Our vet gave us antibotics - injections to give a couple times a day, for over the weekend. Will their appetities improve? Should I be concerned about the vomiting and not eating?
I would be VERY concerned about vomiting and not eating, and in my opinion these dogs need to be hospitalized through the weekend, to receive IV fluids, as dehydration is likely, and will worsen their overall prognosis.

Doxycycline can definitely cause stomach upset, especially when given on an empty stomach.
Customer: replied 6 years ago.
You stated this is caused by the baby heartworms dying in the bloodstream. Does this mean, if we can get thru this, they will no longer have heartworms? When I read the pamphlet it stated the Trifexis would kill the heartworm larvae before they mature - so I am just so surprised one small dose of this has created such a problem.
There are still adult heartworms present which will need proper treatment. Trifexis is intended to kill young worm larvae, but the anaphylactic reaction comes from the "newborn" baby worms, for lack of a better term. These worms are known as microfilaria. It is the dying microfilariae that induce the reaction.
Dr. Drew and other Dog Veterinary Specialists are ready to help you
Customer: replied 6 years ago.
You have answered many of my questions. Thanks, Janice
Janice, I'm glad to be able to help. I'm going to head to bed soon, but I'll be available most of the day tomorrow, starting at around 7AM eastern time if you need anything.