Adverse reactions and interactions with aspirin. Considerations in the treatment of the elderly patient.

Aspirin (acetylsalicylic acid) is probably the most frequently used medication, and its use is generally uneventful. However, aspirin is also noted for numerous side effects and drug interactions that can complicate the course of therapy. The elderly, especially those with complicated medical histories, are more prone to the adverse effects of salicylates and may develop gastrointestinal tract bleeding, renal insufficiency, asthma and CNS toxicity. In the clinical situation, important drug interactions can occur with concurrent use of anticoagulants, sulphonylureas, diuretics, methotrexate and antacids. In long term aspirin therapy, enteric-coated or nonacetylated forms of aspirin are associated with fewer side effects and may be better tolerated. Monitoring of therapy (especially in the higher risk patient), with frequent assessments of the clinical state and measurements of serum creatinine, electrolytes and salicylate concentrations, may diminish the likelihood of toxicity.