The influence of solubility on the rate of gastrointestinal absorption of aspirin.

Abstract

The blood plasma concentration of salicylate 10, 20, 30, 45, and 60 minutes following the oral ingestion of 0.64 Gm. of aspirin in various pharmaceutical preparations was determined in a total of 168 experiments on 55 normal human subiects and used as an index of the rate of gastrointestinal absorption. Aspirin was absorbed relatively slowly, maximum blood levels not being attained at the end of 60 minutes. "Buffered" LWpirin preparations containing aluminum and magnesium "buffers" were somewhat more rapidly absorbed, maximum blood levels being attained at 30 to 45 minutes. A commercially available etfervescent preparation containing aspirin, which must be dissolved prior to ingestion, was still more rapidly absorbed, yielding maximum blood levels at 20 to 30 minutes. Similar results were obtained when aspirin was dissolved in hot water. To extend these observations soluble sodium acetylsalicylate was prepared by neutralizing aspirin with an equivalent amount of sodium bicarbonate. This was also rapidly absorbed. It is concluded that the rate of gastrointestinal absorption of aspirin is markedly influenced by solubility.