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Senior dog with heart murmur panting after Frontline. What to do?

Updated on September 23, 2025

Pet's info: Dog | Mixed Breed Small (up to 22lb) | Male | neutered | 18 lbs

my dog is a pom mix, he's 15, has a heart murmur and fleas. my vet said to give him frontline. i did a few hours ago and now he has a rapid heart rate and is panting hard. any suggestions? it is humid here and he has long hair which doesn't help.

2 Answers

Most Helpful Answer

Answered By Daniel Fonza, DVM

Veterinarian

Published on September 19, 2017

Hello there and thank you for your post! I have not seen these symptoms with Frontline before. The temperature may be a factor so I would make sure that the temperature is cool enough for him and place a fan on him. I am concerned that he may be having a reaction to the front line. If this is a reaction it could potentially become much worse. I would suggest getting him examined by a veterinarian to ensure everything is okay. Especially with a heart murmur, I would want to make sure that these are not symptoms of congestive heart failure. I hope this helps and I hope that he is okay. Please feel free to contact me if you have any other questions or concerns. I am also available by phone or text based consultation if needed

1Pet Parents found this answer helpful

Related Answers from Veterinarians

Answered By David Darvishian
Veterinarian
Hi and thanks for using Petco Pet Education Center, formerly Petcoach! So sorry to hear about Rommel. Just based on this information, I would have to advise that you get Rommel seen as soon as you can. Small breed dogs with acquired heart murmurs (I'm assuming here) can go into congestive heart failure while on medicines for this condition and especially if not on any medicines for this heart problem. You can try getting him more comfortable in a cooler environment with less humidity and see if that helps but if that doesn't help rather quickly, then I would advise calling your veterinarian or your local emergency vet if it's after hours. Rommel may be developing some fluid in his lungs which can happen when in congestive heart failure. Your vet would most likely advise bloodwork, urinalysis, xrays, and ultrasound to assess his heart. Other tests include EKG and possibly a measurement of blood pressure. He may need to be put on a diuretic and some heart medicines to help his heart and prevent fluid accumulation in his lungs. Good luck with Rommel
1Pet Parents found this answer helpful

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