Heartworm preventative Heartgard Plus

Along with monthly Sentinel, Heartgard Plus is among the most commonly prescribed monthly heartworm preventatives by veterinarians.  While both are very effective against protecting against heartworms, Heartgard seems slightly more effective in treating and preventing roundworms and hookworms, while Sentinel offers the protection against whipworms, which occur more sporadically across the United States.

Heartgard Plus heartworm preventative Puppies and/or kittens can be safely started on Heartgard typically at age 8-12 weeks, especially important during a time when roundworms and hookworm infestations are common.  Heartgard Plus does seem to have a long shelf life of 1-2 years. It comes in very convenient dosing package sizes of up to 25 pound dogs, 26 to 50 pound packaging/dosing, and 51-100 pound packaging and dosing.   It is quite safe to use the up to 25 pound size even in small breeds, as owners often wonder if splitting the pill is needed in toy breeds, which is not necessary.

Side effects are indeed rare, but on occasion pets can have rare digestive, dermatologic, and even more rare neurological side effects.  If any of these should occur, I would ask your veterinarian for a prescription for monthly Sentinel as an alternative. It is safe to be on  Heartgard Plus if another dewormer is needed in a dog, such as Panacur C.

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  1. I would certainly agree, heartgard is one of the better products on the market. However, you have to watch out, if your pup has a beef allergy. They no longer make the unflavored kind, so you may have to go with a different brand, if that’s the case.

  2. Dr. Michael Dym, VMD veterinarianMarch 13, 2011 at 11:33 am

    Yes. Hopefully in future and wiht enough consumer pressure the nonchewable heartguard product will return.

  3. So Dr. Dym, can you please confirm what I understand your advice above to be : that it is indeed safe to use another broad spectrum de-wormer like D-Worm Combo (pyrantel parnoate/praziquentel) while on monthly Heartgard therapy? From what I understand, Heartgard will not kill every kind of common parasitic worm dogs can catch, correct?

    Many thanks for your advice, and love your blog.

  4. Dr. Michael Dym, VMD veterinarianNovember 27, 2011 at 11:52 pm

    Hi Cynthia. Thanks for your kind comments regarding the blog. Heartguard does not kill every kind of parasite, however heartguard plus does contain pyrantel , so using D-worm combo would be somewhat redundant. If tapes a problem, using a wormer with only praziquantel or droncit name brand would be sufficient. In fact panacure for 3 days would be better choice for whips and Giardia if they were a problem in the dog.

  5. Is there an optimum time (or time I should NOTadminister) an adjunct wormer, or does it not matter? I administer Heartgard around the 15th of each month. Should I use an adjunct dewormer as a preventative measure (say, once a quarter) or only when the dogs present symptoms – like scooting on the ground and excessive licking? Thanks so much.

  6. Dr. Michael Dym, VMD veterinarianNovember 29, 2011 at 6:08 pm

    I would just stick with heartguard which does control, treat and prevent hookworms and roundworms. No need to routinely use or overuse other wormers unless you see tapeworms in stool or around anus, or if there is history of whipworms.

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  8. Has the non flavored heartguard come back on the market yet? If not, are there any other non flavored oral heartworm preventatives?

    I do NOT want to use the topicals.

  9. Dr. Michael Dym, VMD veterinarianDecember 11, 2012 at 7:41 pm

    Some of the compounding pharmacies may have nonflavored heartworm meds but I am not sure if they are back on market yet. Perhaps try Wedgewood pharmacy which you can google on line.

  10. I’m wondering what the symptons are of the neurological disorder of Heartgard in dogs

  11. Dr. Michael Dym, VMD veterinarianMay 1, 2013 at 9:31 pm

    Not sure I understand your question. Heartguard only in rare situations can cause neurological reactions such as weakness, wobbliness, seizures, etc

  12. Found some Heartguard from 2010, is it any good or should I pitch it? A box of 6 so not happy about it.. Thanks for info.

  13. Dr. Michael Dym, VMD veterinarianAugust 25, 2013 at 9:26 pm

    I would not use a box of heartworm this old. May have lost potency.

  14. My senior rescue labrador (7+) tested positive for heartworms. Rather than put him through the quick and sometimes difficult treatment, we opted to use Heartguard. After about 8 months he was negative for larvae but still heartworm positive. My vet changed him to Sentinel about 2 months ago. Is this acceptable when trying to treat the adult worms?

  15. Dr. Michael Dym, VMD veterinarianAugust 17, 2014 at 2:05 pm

    Using sentinel is fine.

  16. I found two doses of Heartgard Plus in the pantry with an expiration date of June, 2013. I know expirations are often actually “sell-by” dates. Can I use these doses for my dogs this month or are they too old? Thank you.

  17. Dr. Michael Dym, VMD veterinarianSeptember 15, 2014 at 4:11 pm

    The doses are probably fine, but given the legalities I can recommend you use these meds since they have officially expired.

  18. Does heart guard medication lose potency after self life?

  19. Dr. Michael Dym, VMD veterinarianMarch 18, 2015 at 1:06 pm

    I dont think it does, but as licensed veterinarians, we must recommend NOT using any products that are out of date. Would be illegal.

  20. I give my dog Heartgard every month. She was just diagnosed with roundworm. Doesn’t Heartgard prevent roundworm?

  21. Heartguard does indeed control and prevent roundworms as well. There must be heavy infestation in the environment for her to shed eggs. The pyrantel and ivermectin in heartguard are excellent against this parasite. I assume your dog was not likely clinically sick with roundworms, or perhaps you saw the roundworms pass out after administering a heartguard tablet which can also occur. I would continue the monthly heartguard

  22. I two boxes of Heartguard plus that will expire next month. How long can I still use them.

  23. Hi Sandra. We do not recommend using expired medication. If you ordered these through us, please just give us a call at 1-800-738-6337 to issue you a refund or replacement!
    ~ Abby, PetMeds Pro

  24. Hi Doc, I have an unopened box of Heartgard (6 doses) that expired 10 months ago. I understand this is still usable?
    Instead of using them for the next 3 months for my 2 dogs, I am considering alternating them with unexpired ones for the next couple of months. Possibly at 3-week intervals instead of the usual monthly intervals, in case of loss of potency,
    Your thoughts please? Thanks.

  25. It is never recommended to use expired medications. If you ordered through us, please contact us for a full refund for the unused/expired medication.
    ~ Abby, PetMeds Pro

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