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Absorption Pharmacokinetics (pharmacology and toxicology)

  1. Pharmacology and Toxicology (Pharmacokinetics) By - Devendra kumar Rawat Assistant Professor M.Pharm (Pharmacology) B.M.S. College of Pharmacy, Nasratpur, Tiloi, Distt.-Amethi 1
  2. Pharmacokinetics Pharmacokinetics is the quantitative study of drug movement in, through and out of the body. The intensity of response of drug is depends on the pharmacokinetic properties of drug. It deals with the ADME –  Absorption,  Distribution,  Metabolism and  Excretion of drugs Absorption & Distribution are influenced by the formulation. 2 Devendra Kumar Rawat
  3. Pharmacokinetics 3 Devendra Kumar Rawat Schematic depiction of pharmacokinetic process
  4. Pharmacokinetics  Absorption :  Absorption is movement of the drug from its site of administration into the circulation.  The drug molecules in their transfer from the site of administration to the blood have to cross a complex biological barrier composed of lipids, proteins, lipo – proteins, polysaccharides, etc.  This barrier is semi permeable biological membrane. 4 Devendra Kumar Rawat
  5. Biological membrane This is a bilayer (about 100 Å thick) of phospholipids and Cholesterol molecules. oHead end – Hydrophilic (water loving) oTail end – Hydrophobic (water hating or lipid loving) 5 Devendra Kumar Rawat
  6. Biological membrane 6 Devendra Kumar Rawat
  7. Pharmacokinetics  Absorption  Mechanism of drug absorption :  The drugs can pass through cell membrane by two processes, they are - I. Passive transfer i. Simple diffusion ii. Filtration II. Specialized transfer i. Active transport ii. Facilitated diffusion iii. Pinocytosis 7 Devendra Kumar Rawat
  8. Pharmacokinetics Difference between Passive transport & Active Transport 8 Devendra Kumar Rawat Particulars Passive Transport Active Transport Concentration Gradient From Higher concentration to lower concentration From lower concentration to higher concentration Carrier No need of carrier Needs carrier Energy No energy required Energy required as ATP Efficiency of the process It is a slow process It is a rapid process Directionality Bidirectional process Occurs in one direction
  9. Pharmacokinetics  Absorption I. Passive transfer : This process does not require any energy. i. Simple diffusion :  The drug diffuses across the membrane in the direction of its concentration gradient i.e. 9 Devendra Kumar Rawat High Low
  10. Pharmacokinetics  Absorption i. Simple diffusion :  Water soluble drug (ionized or polar) is readily absorbed via aqueous channels or pores in cell membrane.  Lipid soluble drugs ( non ionized or non polar) is readily absorbed via cell membrane itself. 10 Devendra Kumar Rawat
  11. Pharmacokinetics  Absorption ii. Filtration :  Filtration is passage of drugs through aqueous pores in the membrane or through paracellular spaces.  Lipid insoluble drugs cross biological membranes by filtration if their molecular size is smaller than the diameter of the pores. 11 Devendra Kumar Rawat
  12. Pharmacokinetics  Absorption II. Specialized transport :  It requires energy. i. Active transport  It is a selective process which requires energy in the form of Adenosine triphosphate (ATP).  It also requires a carrier to transfer drug, so is also called “carrier transport”. 12 Devendra Kumar Rawat Low High
  13. Pharmacokinetics  Absorption II. Specialized transport : ii. Facilitated diffusion  It is similar to carrier transport but it does not require energy.  Carriers used in this diffusion are solute carrier transporter (SLC), moves poorly diffusible substrates. 13 Devendra Kumar Rawat High Low
  14. Pharmacokinetics  Absorption II. Specialized transport : iii. Pinocytosis  It is the process of transport across the cell by formation of vesicles.  Proteins and macromolecules are transported by this process.  In this cells engulf the macromolecules from ECF. 14 Devendra Kumar Rawat