Physiological effects, aspirin

Salicylic acid is mainly responsible for the toxic effects of aspirin, and it has a number of metabolic and physiological effects some of which are interrelated (Fig. 7.58) ... 

Aspirin (acetylsalicylic acid) and other salicylates are still a common cause of human poisoning, both therapeutic and suicidal, and account for a significant number of deaths each year. Although the toxic effects have a biochemical basis, some of the effects caused are clearly physiological, and consequently, it has been used as an example in this category. 

Salicylamide reportedly exerts a moderately quicker and deeper analgesic effect than aspirin. Long-term studies on rats revealed no untoward symptomatic or physiological reactions. Its metabolism differs from that of other salicylic compounds, and it is not hydrolyzed to salicylic acid." Its analge.sic and antipyretic activity is probably no greater than that of aspirin, and possibly less. It can be used in place of salicylates, however, and is particularly useful for patients with a demonstrated sensitivity to salicylates. It is excreted much more rapidly than other salicylates, which probably accounts for its lower toxicity and. thus, does not permit high blixHl levels. 

Aspirin (acetylsalicylic acid) provides an example of a pharmacologic drag that exerts its effect throngh the covalent acetylation of an active site serine in the enzyme prostaglandin endoperoxide synthase (cycloxygenase). Aspirin resembles a portion of the prostaglandin precnrsor that is a physiologic substrate for the enzyme. 

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