Aspirin ADME

Stable Identifier
Homo sapiens
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In water aspirin (acetylsalicylic acid, ASA) dissolves, dissociating into the acetylsalicylate ion (ASA-). ASA- is an anti-clotting agent and nonsteroidal anti-inflammatory drug (NSAID); the therapeutic effects are mediated through its interaction with PTGS enzymes. On a molar basis ASA- (a) is more potent as an analgesic/anti-inflammatory agent, (b) has greater gastric ulcerogenic activity, and (c) is much more effective as an inhibitor of prostaglandin biosynthesis and platelet aggregation than salicylate (ST) (Flower 1974; Mills et al, 1974; Rainsford 1975; Rainsford 1977).
Acetylsalicylic acid is only slightly soluble in conditions being found in the stomach mucosa, mostly because of unavailability of sufficient amount of solvent. The absorption, as well as the absorbing area, increases in the small intestine. Further increased absorption is achieved by dissolving tablets before ingestion or usage of ASA salts (Dressman et al, 2012). Practically 100% of therapeutic aspirin doses are taken up, mostly by intestinal mucosal cells (Artursson & Karlsson, 1991; Yee 1997).
Only a few percent of ASA- remain unchanged, the rest is hydrolyzed to salicylate (ST). The major route of ST catabolism is conjugation with glycine to form salicyluric acid. This accounts for 20–65% of the products. Conjugation to glucuronides (ester and ether) removes up to 42% of ST. Finally, a minor part also gets hydroxylated by cytochromes (Hutt et al, 1986).
Literature References
PubMed ID Title Journal Year
3888490 Clinical pharmacokinetics of the salicylates

Needs, CJ, Brooks, PM

Clin Pharmacokinet 1985
602882 The comparative gastric ulcerogenic activities of non-steroid anti-inflammatory drugs

Rainsford, KD

Agents Actions 1977
1673839 Correlation between oral drug absorption in humans and apparent drug permeability coefficients in human intestinal epithelial (Caco-2) cells

Karlsson, J, Artursson, P

Biochem Biophys Res Commun 1991
4823623 The effects of some salicylate analogues on human blood platelets. 1. Structure activity relationships and the inhibition of platelet aggregation

Philp, RB, Mills, DG, Hirst, M

Life Sci 1974
22674043 Biowaiver monograph for immediate-release solid oral dosage forms: acetylsalicylic acid

Polli, JE, Kopp, S, Langguth, P, Barends, DM, Abrahamsson, B, Nair, A, Shah, VP, Groot, DW, Dressman, JB, Zimmer, M

J Pharm Sci 2012
4208101 Drugs which inhibit prostaglandin biosynthesis

Flower, RJ

Pharmacol Rev 1974
1980 The biochemical pathology of aspirin-induced gastric damage

Rainsford, KD

Agents Actions 1975
9210194 In vitro permeability across Caco-2 cells (colonic) can predict in vivo (small intestinal) absorption in man--fact or myth

Yee, S

Pharm Res 1997
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