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Decreased serum salicylate concentrations in children with rheumatic fever treated with antacid
Insights
Giving antacids with aspirin may lower serum salicylate levels in children with rheumatic fever due to increased renal clearance. However, this effect was not observed in healthy adults.
Area of Science:
- Pharmacology
- Clinical Therapeutics
- Drug Interactions
Background:
- Salicylate therapy is common for rheumatic fever.
- Antacids are frequently co-administered with salicylates.
- The impact of antacids on serum salicylate levels requires clarification.
Purpose of the Study:
- To investigate the effect of a common antacid (aluminum and magnesium hydroxide) on serum salicylate concentrations.
- To assess whether antacid co-administration alters salicylate bioavailability or clearance.
Main Methods:
- Three children with rheumatic fever received concomitant antacid and aspirin therapy.
- Five healthy adult volunteers also received concomitant antacid and aspirin.
- Serum salicylate concentrations and urinary pH were monitored.
Main Results:
- In children with rheumatic fever, serum salicylate concentrations decreased by 30-70% with antacid co-administration.
- Urinary pH significantly increased in these children.
- Healthy adult volunteers showed no change in aspirin bioavailability.
Conclusions:
- Antacids can significantly reduce serum salicylate concentrations in children with rheumatic fever.
- This reduction is attributed to increased renal clearance of salicylate, driven by elevated urinary pH.
- The interaction may differ between pediatric patients with rheumatic fever and healthy adults.
Abstract:
To determine if the common practice of giving antacids to patients on salicylate therapy has an effect on serum salicylate concentrations, we gave a widely used antacid, aluminum and magnesium hydroxide, and aspirin concomitantly to three children with rheumatic fever. Urinary pH increased appreciably, and serum salicylate concentrations decreased by 30 to 70 per cent. In five healthy adult volunteers concomitant administration of antacid had no effect on the bioavailability of aspirin. Pharmacokinetic analysis revealed that the antacid-induced decrease of serum salicylate concentrations was due to increased renal clearance of salicylate caused by the rise in urinalry pH.