Salsalate kinetics in patients with chronic renal failure undergoing hemodialysis

A 1500 mg dose of salsalate (SSA) was given to five patients undergoing chronic hemodialysis on an interdialytic day and again before dialysis. Compared with control subjects, patients undergoing dialysis had a lower peak plasma SSA level (17 +/- 3 vs. 45 +/- 2 micrograms/ml; P less than 0.01) that occurred slightly later. In contrast, plasma salicylic acid (SA), the active SSA metabolite, had a similar but later peak level that remained substantially higher. Therefore, the AUC for SA was increased by 50% and the SA t1/2 was prolonged in the patients receiving dialysis (8.1 +/- 0.7 vs 3.8 +/- 0.2 hours; P less than 0.01). During a single treatment, dialysis clearance reduced plasma SA levels, removed 18% of total body SA, and returned the SA t1/2 to nearly normal. Because the elimination of SA is impaired in patients undergoing dialysis, the interdialytic SSA dosage should be reduced. Hemodialysis improves SA kinetics and may be followed by a normal SSA replacement dose. However, periodic monitoring of plasma SA levels is recommended when SSA dosing is begun in patients receiving dialysis.