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Effect of antacids on salicylate kinetics
International Journal of Clinical Pharmacology, Therapy, and Toxicology
|September 1, 1985
Summary
Antacids may alter aspirin absorption, particularly at steady-state plasma concentrations. This study found antacids reduced salicylic acid levels and half-life at 15 mg%, impacting aspirin
Area of Science:
- Pharmacokinetics
- Drug Interactions
Background:
- Aspirin (acetylsalicylic acid) is a common analgesic.
- Antacids are frequently used to relieve heartburn and indigestion.
Purpose of the Study:
- To investigate the effect of a common antacid on the absorption and pharmacokinetics of aspirin.
- To determine if antacid use alters aspirin's plasma concentrations and elimination rates.
Main Methods:
- Assessed plasma concentrations of salicylic acid over time (Area Under the Curve - AUC).
- Measured peak plasma concentration (Cmax) and absorption rate constant (Ka).
- Evaluated steady-state kinetics and urine pH in subjects.
Main Results:
- No significant differences in AUC, Cmax, or Ka of salicylic acid were observed initially.
- The antacid altered urine pH in 4 out of 6 subjects.
- At steady-state with plasma concentrations around 15 mg%, the antacid reduced salicylic acid plasma levels and half-life.
Conclusions:
- Antacids can influence aspirin's pharmacokinetics, especially at specific plasma concentrations.
- A urine pH-altering antacid reduces steady-state plasma concentrations and increases elimination of salicylic acid at approximately 15 mg%.