Like people, dogs can suffer from occasional aches and pains related to excess exercise, injuries or arthritis. There are some human over-the-counter (OTC) medications that are safe to give your dog to ease its pain. If the pain persists, you should schedule an appointment with your vet.
Non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin are beneficial for inflammation from arthritis or muscle sprains, while acetaminophen is beneficial for lowering a fever or soothing pain not associated with inflammation.
You should never give your dog ibuprofen, because he can't metabolise it properly. Ibuprofen levels build up and quickly become toxic to dogs.
Dr. Jon Geller, DVM, advises giving acetaminophen at a maximum of 5 mgs per pound of weight three times daily and to use acetaminophen sparingly, due to the potential for kidney and liver damage. Aspirin is given at 10 mgs per pound of body weight up to twice per day.
You should only give your dog plain or buffered aspirin, not enteric-coated. Dogs can't properly digest the enteric coating, which can lead to excess levels of aspirin accumulating in the digestive tract that might cause poisoning.
Both aspirin and acetaminophen can damage the liver, and aspirin is associated with an increased risk of stomach bleeding and ulcers. Neither drug should be used long-term without the recommendation of a veterinarian.