Dosage should be adjusted to your dog’s body weight. As a rule of thumb, a 5-10 milligram dose per pound can be given. This is conservative for most dogs. If your buddy weighs 20 pounds, you’d provide at least 100mg of aspirin but never more than 200mg daily.
Aspirin Use in Dogs and Cats - Pet Education
The recommended dosage of aspirin for dogs varies from 5 to 15 mg per pound once every 12 hours. To minimize the potential for side effects, start on the low side of the scale. Remember, you can always give your dog more aspirin if necessary, up to the recommended dose. Depending on the size of your dog, you may choose to use aspirin specially designed for dogs, baby aspirin (81 mg) or a regular, human-sized aspirin (325 mg). Choose the type of aspirin that is easiest to accurately divide into the appropriate dose. For small-to-medium dogs, this is most likely going to be baby aspirin.
Can You Use Aspirin for Dogs? | PetCareRx
Aspirin can cause digestive bleeding and ulcers in pets, just as it can in humans. If possible, give your dog buffered aspirin to protect its stomach. You should also give aspirin with meals and not on an empty stomach. If your dog stops eating while taking aspirin, appears weak or dizzy, throws up his food or has diarrhea, do not give it any more aspirin and take it to the vet as soon as possible. Also, since aspirin can interfere with blood clotting, do not give it to a dog that is suffering from deep cuts or gashes, or is recovering from surgery. For pain relief after surgery or for long-term pain relief for chronic pain conditions, take your dog to the vet to get appropriate pain medications. If you are giving your dog human aspirin, make sure that it does not contain other human pain relievers or caffeine, as these are extremely poisonous to dogs.
Aspirin Toxicity in Dogs - Pet Health Network