One of the most common side effects of NSAIDs is stomach upset. Usually, this can be avoided by making sure the correct dose is taken and by taking the medicine with food. Eating some crackers or drinking milk just before the medicine is taken is usually enough to avoid a stomach upset. In very rare cases, NSAIDs can cause bleeding problems and their use may need to be stopped before surgery. It is important to let your doctor know if your child has a bleeding disorder, asthma, kidney problems, or is undergoing chemotherapy, or has ever had a stomach ulcer before using NSAIDs.
Ibuprofen and acetaminophen differ in how they work to treat fever, inflammation and pain. Ibuprofen is an NSAID (non-steroidal anti-inflammatory drug) that prevents the body and the brain from producing a hormone-like chemical called prostaglandin. Prostaglandin in the brain is involved in producing fever and prostaglandin in the body is involved in tissue inflammation and the pain that it triggers. Therefore, ibuprofen can reduce fever, pain and inflammation. Acetaminophen is an analgesic (painkiller) and antipyretic (fever reducer) that works in the brain by a mechanism that is not certain. It appears to increase the pain threshold which is the amount of pain it takes for the brain to perceive the pain. It inhibits prostaglandin in the brain only where it is involved in producing fever. Therefore, acetaminophen can reduce fever and pain, but not inflammation.