any salt or ester of
salicylic acid; those used as drugs for their
analgesic,
antipyretic, and
antiinflammatory effects include
aspirin, choline salicylate, magnesium salicylate, and sodium salicylate. Low dosages of salicylates are used primarily for the relief of mild to moderate pain or fever; high dosages are particularly useful for treatment of rheumatoid arthritis and other rheumatoid disorders.
The mechanism of most of the effects of aspirin and other salicylates is inhibition of
prostaglandin synthesis, thus blocking pyretic and inflammatory processes that are mediated by prostaglandins. Aspirin also prolongs bleeding time through its effects on platelets owing to both inhibition of prostaglandin synthesis and acetylation of platelet structures. Salicylates also cause ulceration and hemorrhagic lesions of the gastric mucosa. They act by interfering with the stomach's mucosal barrier (either directly or possibly by an effect on prostaglandins when given parenterally) so that H
+ ions leak and there is subsequent damage. Aspirin should not be taken with alcohol, because this increases gastrointestinal damage. Aspirin should be avoided by persons with gastric ulcers, hemophilia, or hemorrhagic states, and by children with a viral illness.
Another problem associated with the use of salicylates is hypersensitivity. This most commonly occurs with aspirin and is less common with other salicylates. Aspirin-sensitive individuals often also react to other antiinflammatory agents, such as
indomethacin, and to a yellow dye used to color foods and drugs called tartrazine or FD & C Yellow No. 5. The allergic reaction usually takes the form of edema of the face and intestinal tract and asthma. Aspirin sensitivity occurs in about 0.25–1.0 per cent of the population and is more common in persons with a history of asthma or other allergic disorders. There is a common association with nasal polyps.
Salicylate Poisoning. Mild salicylate toxicity, which can occur from high dosage therapy, has symptoms that include headache, dizziness, tinnitus, deafness, nausea, vomiting, and acid-base disturbances. If the poisoning occurs in the home, a
poison control center should be contacted immediately. Large overdoses produce acute poisoning that is a medical emergency. Treatment consists of gastrointestinal decontamination, administration of intravenous fluids to correct dehydration and acid-base imbalance, and hemodialysis if serum salicylate levels are very high. Body sponging with cool water is done for
hyperpyrexia. Blood salicylate levels and blood gases and electrolytes are periodically determined by laboratory tests. Life-threatening poisoning may require exchange transfusion or renal dialysis.