Decreased Serum Salicylate Concentrations in Children with Rheumatic Fever Treated with Antacid

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.

Failure of Prednisone to Aler Plasma Salicylate Concentrations in Dogs

“…Plasma salicylate concentrations are altered by agents such as ammonium chloride, ascorbic acid (l), aminobenzoic acid (2), and "nonsystemic" antacids (3). Among the important drug interactions are those affecting disposition of salicylates.…”

Comparable serum salicylate concentrations from choline magnesium trisalicylate, aspirin, and buffered aspirin in rheumatoid arthritis

“…Although there were no significant differences among the 3 treatments, the buffered aspirin group had the lowest mean steady-state concentrations. This may in part be due to the dose of antacid in each tablet, which could increase urinary pH and thus increase the excretion of salicylate (10).…”

Steady-state serum salicylate levels in hospitalized patients with rheumatoid arthritis

“…Hence, care must be used in finding a daily salicylate dose for an individual. Sufficient time (approximately 7 to 10 days) must be allowed for a new equilibrium to be reached before new increments are undertaken, and attention must be given to factors that may change renal function or urinary pH (12,13).…”