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GENERAL PHARMACOLOGY-absorption of drugs

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GENERAL PHARMACOLOGY-absorption of drugs

  1. 1. Seminar on
  2. 2. DEFINITION “Absorption is defined as the process of movement of unchanged drug from the site of administration to the systemic circulation.”
  3. 3. MECHANISM OF DRUG ABSORPTION 1) Passive diffusion and filtration 2) Specialized transport A) Carrier- mediated transport i) Facilitated diffusion ii) Active transport a) primary active transport b) secondary active transport 3) Phagocytosis 4) Pinocytosis
  4. 4. Passive Diffusion  It is defined as the difference in the drug concentration on either side of the membrane.  Also called nonionic diffusion  It is the major process for absorption of more than 90% of the drugs.  The driving force for this process is the ‘concentration or electrochemical gradient’.
  5. 5. PORE TRANSPORT  It is also called as Convective transport, Bulk flow or filtration.  The driving force for this process is the ‘hydrostatic pressure or the osmotic differences across the membrane’.  The process is important in the absorption of low molecular weight, low molecular size drugs.  Example: Urea, Water, Sugar
  6. 6. CARRIER-MEDIATED TRANSPORT  The mechanism is thought to involve a component of the membrane called as the carrier that binds reversibly or non-covalently with the solute molecules to be transported.  The carrier may be an enzyme or some other component of the membrane.  Two types  Facilitated diffusion  Active transport
  7. 7. FACILITATED DIFFUSION  This mechanism involves the driving force is concentration gradient.  In this system, no expenditure of energy is involved (down-hill transport), therefore the process is not inhibited by metabolic poisons that interfere with energy production.
  8. 8. ACTIVE TRANSPORT  It is process where the materials are transported across membranes against a concentration gradient.  The drug is transported from a region of lower to one of higher concentration i.e.. against the concentration gradient or ‘uphill transport’.  Examples : Sodium, potassium, iron, glucose and vitamins like niacin, pyridoxine and ascorbic acid.
  9. 9. ENDOCYTOSIS  Also called Corpuscular or Vesicular transport  It involves engulfing extracellular materials within a segment of the cell membrane to form a saccule or a vesicle which is then pinched-off intracellularly.  Includes two type of process: Phagocytosis and Pinocytosis
  11. 11. PINOCYTOSIS  This process is important in the absorption of oil soluble vitamins & in the uptake of nutrients.
  12. 12.  Aqueous solubility  Concentration  Area of absorbing surface  Vascularity of absorbing surface  Route of administration
  13. 13. References  Essentials of Medical pharmacology by K.D Tripathi pg;no 12-17.  www.authorstream.com  http://www.google.co.in/images
  14. 14. … Thank you