Aspirin (Acetylsalicylic Acid)

What is Aspirin?

Aspirin, chemically known as acetylsalicylic acid, is a non-steroidal anti-inflammatory drug (NSAID) used to relieve pain, reduce fever, control inflammation, and prevent blood clot formation.

Its unique ability to irreversibly inhibit platelet function makes it a cornerstone therapy in cardiovascular medicine.

History & Origin

The therapeutic roots of aspirin trace back to willow bark, which contains salicin — a natural precursor to salicylic acid. In 1897, chemist Felix Hoffmann synthesized acetylsalicylic acid in a stable and tolerable form, marking a major milestone in drug development.

Chemical Structure & Medicinal Chemistry

• IUPAC: 2-acetoxybenzoic acid
• Molecular Formula: C₉H₈O₄
• Molar Mass: 180.16 g/mol
• Functional Groups: Ester, carboxylic acid, aromatic ring

The acetyl group enables aspirin to permanently acetylate cyclooxygenase enzymes — a mechanism that differentiates it from most other NSAIDs.

Mechanism of Action

Aspirin irreversibly inhibits COX-1 and COX-2 enzymes, blocking the conversion of arachidonic acid into prostaglandins and thromboxane A₂.

• Reduced prostaglandins → less pain, fever, and inflammation
• Reduced thromboxane A₂ → decreased platelet aggregation

Because platelets cannot synthesize new COX enzymes, the antiplatelet effect persists for the lifespan of the platelet (approximately 7–10 days).

Pharmacokinetics

• Rapid gastrointestinal absorption
• Hydrolyzed into salicylic acid in plasma and liver
• Hepatic metabolism via conjugation pathways
• Renal excretion

Clinical Uses

• Mild to moderate pain
• Fever reduction
• Inflammatory disorders such as arthritis
• Prevention of heart attack and ischemic stroke
• Post-cardiac procedure antiplatelet therapy

Safety and Responsible Use

While effective, aspirin should be used cautiously due to its impact on gastric mucosa and platelet function. Taking the medication with food may reduce stomach irritation.

Common Side Effects

• Gastric discomfort
• Heartburn
• Nausea
• Easy bruising

Serious Risks & Warnings

• Gastric ulcers and bleeding
• Reye’s syndrome in children and adolescents
• Hypersensitivity reactions in susceptible individuals

Who Should Use Caution?

• Patients with bleeding disorders
• Individuals with peptic ulcer disease
• Asthmatics sensitive to NSAIDs
• Children with viral infections

Drug Interactions

• Anticoagulants (e.g., warfarin, heparin)
• Other NSAIDs
• Corticosteroids
• Alcohol

Aspirin vs Ibuprofen vs Paracetamol

Aspirin provides anti-inflammatory and antiplatelet effects, ibuprofen offers strong anti-inflammatory activity, while paracetamol is typically preferred when gastric safety is a priority. Clinical choice depends on therapeutic goals and patient risk factors.

References

• World Health Organization (WHO)
• U.S. Food and Drug Administration (FDA)
• PubChem Drug Database
• National Center for Biotechnology Information (NCBI)