Hydrolysis of Salicylsalicylic Acid in Human Blood and Plasma: A Comparison with Acetylsalicylic Acid

Abstract

The hydrolysis in vitro of salicylsalicylic acid and acetylsalicylic acid was investigated in human plasma and whole blood. The rate of hydrolysis in plasma as well as in whole blood was considerably greater for acetylsalicylic acid than for salicylsalicylic acid. Acetylsalicylic acid was hydrolyzed much more rapidly in whole blood than in plasma while salicylsalicylic acid tended to hydrolyze more slowly in whole blood than in plasma. These differences may in part explain the differences in biological half‐life between the two drugs.

Reaction of human albumin with aspirin in vitro: Mass spectrometric identification of acetylated lysines 199, 402, 519, and 545

“…Aspirin hydrolysis in plasma is catalyzed by butyrylcholinesterase. The half-life of aspirin in 0.1 M phosphate buffer, pH 7.4 at 37 °C is 15.4 h [19] vs. 1.6 h in plasma at 37 °C [20] and vs. 0.8 h in whole blood [20]. …”

“…The time difference between treatments corresponds to 5 half-lives of aspirin in vivo [17]; consequently about 96% of the aspirin should have been hydrolyzed in 1 h 40 min. However in isolated plasma aspirin was found to survive longer [20,21]. Thus, 1 hour and 40 minutes is not enough for aspirin to break down completely, meaning that the observed increase in the number of acetylation sites may be due to build up of aspirin concentration.…”