To avoid harmful drug interactions, you should not give aspirin to a dog that is on any other medications unless you're giving aspirin under the direct supervision of a veterinarian. Ask your vet about alternative pain medications so you can make an informed decision about the best treatment for your pet.
PetMD: Can you give a dog Tylenol or other pain meds?
So, to sum up, whilst most pet owners believe that aspirin is a safe medication that they can give to their dog to relieve pain, it is always best to check with the vet for the exact dosage and to take special care if any other medication is being taken at the same time or has been taken recently. Every pet owner wants to ensure that treatment for heartworm is as pain-free for their dog as possible, but do not risk the possibility of causing your pet further problems by trying to help by giving Aspirin without being absolutely sure that it is safe to do so.
Aspirin and Advil for Pain Relief in Dogs - Assisi Loop
The Bayer corporation invented aspirin at the tail end of the 19th century, which you’d assume would make them the pros at it. But any company can make it and distribute it, so if you decide on giving your dog a painkiller meant for humans, you don’t have to give them Bayer, but we’re guessing you have some on hand since you’re asking if it’s alright for them.
Aspirin For Dogs: What You Need to Know - Veterinary Place
Giving a dog aspirin is acceptable if your pet is experiencing pain, fever, or inflammation. Aspirin will provide your pet with relief to his chronic pain or discomfort, but it should be given to dogs with extreme caution. Dogs can't tolerate large amounts of aspirin in the body. Aspirin should also never be given to young puppies, because they cannot process it. Dosage amounts are very important when giving an animal aspirin. An overdose of aspirin can quickly lead to serious complications, and death. The safe amount of aspirin to give to your pet will depend on his size and weight. Always contact a veterinarian before administering aspirin to your pet. Aspirin, even in the smallest dosages, can be extremely poisonous to puppies. Puppies do not have the necessary enzymes required for breakingdown and processing aspirin, and should never be given the pain reliever. Administering aspirin to a puppy can be a lethal mistake, so pet owners should keep the aspirin away from young dogs.