Absorption Of Drugs

Question 1

Definition of absorption of drugs

Answer 1

The process of movement of unchanged drugs from the site of administration to systemic circulation

Question 2

Drug absorption mechanism

Answer 2

1. Passive transport
   -a movement of ions or molecular substance across cell membranes without the need of energy.
   -the molecules move from a region of high concentration to lower concentration
   - exp: lipid soluble drugs readily move across membranes due to their solubility in membrane bilayer.
   Water-soluble drugs penetrate cell membrane through aqueous channels or pores.
2. Active transport
   - movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and required energy.
   - involves specific carrier protein.
   - energy-dependent and driven by the hydrolysis of ATP and ADP.

Facilitated diffusion

• drugs moves from an area of high concentration to an area of low concentration.
• drugs enter through specialized transmembrane carrier protein that facilitate passage of large molecule.
• does not require energy

4. Endocytosis and Exocytosis
   - transports drugs of extra large size across the cell membrane.
   - Endocytosis : involves engulfment of drugs molecule by the cell membrane and transport into the cell by squeezing the drug filled vesicle.
   - exocytosis: reverse of Endocytosis and used by cells to secrete many substance by a similar vesicle formation process.