Excretion of Drugs

Excretion of drugs is the process of eliminating drugs and metabolites mainly via kidneys, bile, or lungs.

Excretion of Drugs

• Excretion is the process by which the drug or its metabolites are removed from the body.

1. Renal Excretion (most common)

   • Glomerular Filtration: Depends on the free drug fraction in plasma (unbound drug is freely filtered).
   • Tubular Secretion: Active transport in the proximal tubule (e.g., secretion of acidic drugs by organic anion transporters, basic drugs by organic cation transporters).
   • Tubular Reabsorption: Passive diffusion of lipid-soluble unionized drugs from the renal tubule back into the bloodstream.

2. Biliary Excretion

   • Drugs or metabolites secreted into bile, then into the intestine.
   • Enterohepatic Recirculation: Some drugs get reabsorbed from the gut, prolonging their half-lives (e.g., certain oral contraceptives).

3. Other Routes

   • Lungs: For volatile anesthetics and gases.
   • Sweat, Saliva, Breast Milk: Minor routes but can still be clinically significant (e.g., drug exposure in nursing infants).

Thank you for reading from Firsthope's notes, don't forget to check YouTube videos!