Does anybody know where in the body aspirin becomes active?

1. Jan 12, 2008

Mitchtwitchita

Does anybody know where aspirin becomes active, the stomach or the intestines? Based on a test I performed, I would conclude that it is the stomach. However, the results of said test weren't very conclusive.

2. Jan 12, 2008

gravenewworld

Aspirin is the active compound. ASA, however, is absorbed in both the stomach and the proximal intestine. ASA is optimally absorbed under basic conditions, thus most of ASA is absorbed in the intestine. ASA itself is not a prodrug, ASA itself is active.

3. Jan 12, 2008

Mitchtwitchita

Thanks Gravenewworld! I had a hunch it was the intestines even though the test led me to believe otherwise.

4. Jan 16, 2008

ghost02

How did you perform this test?

5. Jan 16, 2008

gravenewworld

Actually, I am mistaken. I am getting some of my drugs mixed up. ASA is absorbed at a much faster rate in the intestine. This is because the pH rises in the intestine (compared to the pH in the stomach), thus the carboxyl group on ASA deprotonates. The ionized form of ASA is extremely soluble thus most of the ASA is absorbed in the intestine. In the stomach ASA mostly exists in its protonated form which is not very soluble. Scratch what I said about "basic conditions".

6. Jan 17, 2008

chemisttree

GNW,
I think you had it right the first time. Here's what I found:
http://www.rxmed.com/b.main/b2.phar...phs/CPS- (General Monographs- A)/ASPIRIN.html

7. Jan 17, 2008

chemisttree

There are methods to quantify the absorption by both the stomach and the duodenum (and jejunum or ileum). The method I am familiar with is the Delusio (spelling?) technique where the major vein leading from the intestine to the liver is cannulated and blood samples withdrawn. The intestine is cleaned and rinsed with normal saline and the proximal and distal ends of a section (take your pick between one or more of duodenum, jejunum and ileum) are connected to a circulating bath of the drug. Samples can be removed both as blood and from the recirculating bath.