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Page: Aspirin
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Aspirin, or acetylsalicylic acid (IPA: [??s?tl?s?l??s?l?k ??s?d]), (acetosal) is a drug in the family of salicylates, often used as an analgesic (to relieve minor aches and pains), antipyretic (to reduce fever), and as an anti-inflammatory. It also has an antiplatelet ("blood-thinning") effect and is used in long-term, low doses to prevent heart attacks and cancer.
Low-dose, long-term aspirin use irreversibly blocks the formation of thromboxane A2 in platelets, producing an inhibitory effect on platelet aggregation. This anticoagulant property makes it useful for reducing the incidence of heart attacks. Aspirin produced for this purpose often comes in 75 or 81 mg, dispersible tablets and is sometimes called "junior aspirin" or "baby aspirin." New evidence suggests[citation needed] that baby aspirin may not be as effective in preventing heart attacks and cerebrovascular accidents as previously thought. High doses of aspirin are also given immediately after an acute heart attack. These doses may also inhibit the synthesis of prothrombin and may, therefore, produce a second and different anticoagulant effect, but this is not well understood.
Its primary, undesirable side-effects, especially in higher doses, are gastrointestinal distress (including ulcers and stomach bleeding) and tinnitus. Another side-effect, due to its anticoagulant properties, is increased bleeding in menstruating women. Because there appears to be a correlation between aspirin and Reye's syndrome, aspirin is no longer used to control flu-like symptoms or the symptoms of chickenpox in minors.
Aspirin was the first-discovered member of the class of drugs known as non-steroidal, anti-inflammatory drugs (NSAIDs), not all of which are salicylates, though they all have similar effects and a similar action mechanism.
Aspirin
Aspirin is commercially synthesized using a two-step process. First, phenol (generally extracted from coal tar) is treated with a sodium base which generates sodium phenoxide, which is then reacted with carbon dioxide under high temperature and pressure to yield salicylate, which is acidified, yielding salicylic acid. This process is known as the Kolbe-Schmitt reaction.
Salicylic acid is then acetylated using acetic anhydride, yielding aspirin and acetic acid as a byproduct. It is a common experiment performed in undergraduate organic chemistry practicals, and generally tends to produce low yields due to the relative difficulty of its extraction from an aqueous state. The trick to getting the reaction to work is to acidify with phosphoric acid and heat the reagents under reflux with a boiling water bath for between 40 to 60 minutes.
The original synthesis of aspirin from salicylic acid involved acetylation with acetyl chloride. Unfortunately, the byproduct from this is hydrochloric acid, which is corrosive and environmentally hazardous. As described above, it was then later found that acetic anhydride was a better acylating agent, with the byproduct acetic acid formed, which does not have the unwanted properties of hydrochloric acid and can also be recycled. The salicylic acid/acetic anhydride method is commonly employed in undergraduate teaching labs.
Formulations containing high concentrations of aspirin often smell like vinegar. This is because aspirin can undergo autocatalytic degradation to salicylic acid in moist conditions, yielding salicylic acid and acetic acid.
The acid dissociation constant (pKa) for Acetylsalicylic acid is 3.5 at 25 °C. ASA, being a weak acid, dissociates as shown by the following reaction equation:
• Heart Problems - Aspirin...
• Heart Problems - Aspirin as Genericized Trademark...
• Heart Problems - Discovery...
• Heart Problems - Synthesis...
• Heart Problems - Mechanism of Action...
• Heart Problems - Indications...
• Heart Problems - Toxicity of Low-dose Aspirin...
• Heart Problems - Contraindications and Warnings...
• Heart Problems - Common Side-effects...
• Heart Problems - Interactions...
• Heart Problems - Overdose...
• Heart Problems - Research Into Cancer Prevention...
• Heart Problems - Aspirin in Pets...
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Important notice:
The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other
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