Nonsteriodal anti-inflammatory drugs (NSAIDs) such as aspirin are considered analgesic drugs, or medications that reduce pain and fever without inducing unconsciousness. Analgesics work by interfering with pain signals transmitting to the brain or interfering with how the brain receives pain signals. Aspirin and other NSAIDs also decrease the production of chemical prostaglandins in the body. Prostaglandins are naturally occurring enzymes that cause smooth muscle cells to constrict and dilate, heightening pain sensations in some situations. Aspirin and NSAIDs such as ibuprofen and naproxen are available without a doctor's prescription in most places, and they are widely used for pain relief and fever reduction.
Salicylic acid, from which aspirin is derived, comes from the bark of the willow tree and spirea shrub. Hippocrates, in the fourth century BC, described the use of willow bark and leaves for curing headaches and fevers. It wasn't until the late 19th century that aspirin was developed into prepackaged powder form. It became a popular antipyretic, or fever-reducing drug, for treating the high fevers associated with the Spanish Flu pandemic of 1918. Aspirin causes stomach upset in sensitive users, so some people use the gentler ibuprofen or acetaminophen, which is not an NSAID, to reduce fever.
NAIDs such as ibuprofen and naproxen are more modern non-narcotic drugs than aspirin and are used for the same purposes: reducing fever and inflammation and relieving pain. In higher doses, aspirin and NSAIDs of other types will all reduce inflammation, but modern NSAIDs are gentler on the digestive tract and do not thin the blood. Aspirin is the only NSAID able to inhibit COX-1 and platelet aggregation, and it is used primarily as a blood thinner for patients who have heart disease or who are susceptible to heart disease or stroke. Other NSAIDs increase the risk of stroke and heart attack, and studies have shown that these drugs can inhibit the blood-thinning capabilities of aspirin when they are consumed together.
As with aspirin, other NSAIDs interfere with the production of prostaglandins. Ibuprofen has shown to be a very effective NSAID for reducing fever. Aspirin should never be given to children under 16 who have influenza or varicella, because the salicylic acid damages the liver and causes fatal encephalitis. The choice between aspirin and NSAIDs such as ibuprofen is largely a matter of tolerance and medical needs. Patients who are at risk for heart disease typically are given aspirin, but patients who have sensitive stomachs or blood-thinning concerns are given other NSAIDs.
Aspirin and NSAIDs of other types are associated with severe side effects when they are taken for long periods of time or in excessive doses. The most common problems are nausea, digestive problems, shortness of breath, dizziness and skin rash. Severe side effects include stomach ulcers, gastrointestinal bleeding or perforation, prolonged bleeding after injury and liver or kidney failure. Generally, patients who are allergic to one NSAID are allergic to all other NSAID.