Welcome! I am Dr. Altman, a licensed veterinarian and happy to answer your questions today.
Luckily heartworm medication is very safe and tested with 5-10 x the recommended dose to ensure that it is not toxic
if large volumes are ingested.
Depending on the brand of heartworm prevention (there are about 5 varieties) most common clinical signs of ingestion of large volumes
Loss of appetite
If you see anything more than the lethargy, vomiting, diarrhea, reduced appetite in the next 24 hours then it would be best to have your little one seen but in general these medications are very safe and I would not expect to see any side effects
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