Aspirin

Structure of Aspirin

Aspirin, chemically known as acetylsalicylic acid, has a simple structure consisting of a benzene ring with two functional groups:

• Acetoxy group (–COOCH3)
• Carboxylic acid group (–COOH)

The molecular formula of aspirin is C9H8O4, and it is synthesized through the esterification of salicylic acid with acetic anhydride.

Mechanism of Action

Aspirin’s primary mechanism of action is the inhibition of cyclooxygenase enzymes (COX-1 and COX-2). These enzymes are responsible for converting arachidonic acid into prostaglandins, which mediate inflammation, pain, and fever. By blocking COX enzymes:

• Pain relief occurs by reducing the production of prostaglandins involved in pain signaling.
• Anti-inflammatory effects are due to the reduction of inflammatory mediators.
• Antipyretic (fever-reducing) effects arise by lowering prostaglandin levels in the hypothalamus.

Aspirin irreversibly inhibits COX-1, which is essential for platelet aggregation, and therefore, it also acts as an antiplatelet agent.

Common Uses of Aspirin

Aspirin is used for a variety of medical conditions:

1. Pain Relief

It is effective for mild to moderate pain, such as headaches, muscle aches, and toothaches.

2. Anti-inflammatory

It is used in the treatment of conditions like rheumatoid arthritis and osteoarthritis to reduce swelling and joint pain.

3. Fever Reduction

It is commonly used to reduce fever, especially in adults, by targeting the underlying inflammatory processes.

4. Cardiovascular Protection

It is frequently prescribed in low doses to prevent heart attacks, stroke, and blood clots by inhibiting platelet aggregation.

Side Effects of Aspirin

While it is beneficial, it can cause several side effects, particularly when used long-term or in high doses.

1. Gastrointestinal Issues

• Stomach irritation and ulcers are common side effects.
• Bleeding risk due to the anticoagulant effect.

2. Allergic Reactions

Some individuals may experience rash, swelling, or difficulty breathing (anaphylaxis).

3. Kidney and Liver Damage

Chronic use of aspirin, especially in high doses, may lead to kidney and liver dysfunction.

4. Reye’s Syndrome

It should not be given to children under 18 with viral infections (e.g., flu, chickenpox), as it increases the risk of Reye’s syndrome, a rare but serious condition affecting the liver and brain.

Contraindications of Aspirin

Aspirin is contraindicated in several situations:

1. Active gastrointestinal bleeding or a history of ulcers.
2. Severe liver or kidney impairment.
3. Hypersensitivity to aspirin or NSAIDs.
4. Children with viral infections due to the risk of Reye’s syndrome.

Drug-Drug Interactions of Aspirin

It can interact with a number of drugs, affecting its effectiveness and increasing the risk of adverse effects.

1. Anticoagulants (e.g., warfarin)

Aspirin increases the anticoagulant effects, raising the risk of bleeding.

2. Other NSAIDs

Using aspirin in combination with other NSAIDs (e.g., ibuprofen) can increase the risk of gastrointestinal bleeding and kidney damage.

3. Diuretics and ACE Inhibitors

Aspirin can reduce the effectiveness of certain diuretics and ACE inhibitors by impairing kidney function.

4. Methotrexate

Aspirin may increase methotrexate levels in the blood, leading to toxicity.

Dosage of Aspirin

The dosage of aspirin depends on the condition being treated:

• For pain relief and fever: Typically, 325 to 650 mg every 4 to 6 hours as needed. Thus, maximum dosage should not exceed 4,000 mg per day.
• For cardiovascular protection: A low dose of 81 mg (often referred to as “baby aspirin”) is commonly recommended for stroke and heart attack prevention.
• For inflammatory conditions: Doses can range from 1,000 mg to 3,000 mg per day, divided into smaller doses.

Hence, always consult a healthcare provider before starting or adjusting the dosage.

Popular Brand Names of Aspirin

It is sold under numerous brand names, including:

• Bayer Aspirin
• Excedrin (combination with acetaminophen and caffeine)
• Bufferin
• Ascriptin
• Ecotrin (enteric-coated aspirin)

These brands may vary in formulations (e.g., regular vs. enteric-coated) but contain the same active ingredient—acetylsalicylic acid.

Conclusion

Aspirin is a versatile medication with a broad range of applications, from pain relief to cardiovascular protection. While generally safe, it can cause side effects and interact with other drugs, requiring careful use. As with any medication, it is essential to follow recommended dosages and consult a healthcare provider to ensure its safe and effective use.