Aspirin's Journey in the Body

Aug 22, 2024

The Journey of Aspirin Through the Digestive System

Overview

  • Aspirin tablet travels through the digestive system after swallowing.

Journey Through the Digestive System

  • Esophagus: Aspirin travels down the esophagus.
  • Stomach:
    • Aspirin dissolves into smaller particles.
  • Small Intestine:
    • Most particles are absorbed into the blood.
    • Small intestine walls (Lumen) lined with tiny Villi.
    • Villi increase surface area for nutrient absorption.

Structure of Villi

  • Rich blood supply.
  • Covered in a thin layer of epithelial cells.
  • Aspirin molecules pass through epithelial cells into the bloodstream.

Bloodstream Distribution

  • Albumin:
    • A protein made by the liver that transports nutrients and binds to drugs.
    • Aspirin molecules bind to albumin in the blood plasma.
  • Liver Filtering:
    • Aspirin bound to albumin is filtered out by the liver.
    • Only unbound aspirin molecules affect the body.

Liver Metabolism

  • Hepatic Portal Vein: Aspirin-rich blood enters the liver.
  • Hepatic Vein: Blood exits the liver.
  • First Pass Metabolism:
    • The liver metabolizes drugs before they reach the body.

Phases of Metabolism

  1. Phase 1 Metabolism:
    • Aspirin is hydrolyzed, producing salicylic acid.
    • Salicylic acid is not water-soluble.
  2. Phase 2 Metabolism:
    • Ionized group added to salicylic acid forming glucuronide.
    • Glucuronide is water-soluble and can be excreted in urine.

Bioavailability

  • Only 68% of orally taken aspirin has an effect due to filtering.
  • This percentage is known as the drug's oral bioavailability.
  • Drugs administered through other methods (e.g., intravenously) bypass liver filtering, achieving 100% bioavailability.

Effect on Pain and Inflammation

  • Prostaglandins:
    • Produced in damaged skin tissues, causing inflammation and pain sensation.
  • Aspirin's Role:
    • Prevents production of prostaglandins, reducing swelling and pain signals.

Excretion of Aspirin

  • Remaining aspirin in blood circulates until used or filtered out.
  • Travels to the kidneys and then to the bladder for excretion.