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General principles of drug action
 

General principles of drug action

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uploaded by : Morteza Parmis

uploaded by : Morteza Parmis

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    General principles of drug action General principles of drug action Presentation Transcript

    • Chapter 2 General Principles of Drug Action
    • General Factors that Characterize the action of all Drugs and that Determine the effective level of any Therapeutic agent at its site of action
      • Route of administration
      • Passage across body membrane
      • Absorption
      • Transport and distribution
      • Molecular mechanism of drug action
      • Drug metabolism
      • excretion
    • A. Route of administration
      • General Routes of Drug Administration
      • I. Enteral- (Oral and Rectal)
      • Oral
      • Dosage forms: tablet, capsule, suspension,
      • solution, pills etc.
      • Area of Absorption: gastric and intestinal mucosa
    • oral
      • Advantages
      • - Safest
      • - Most convenient
      • - Cheapest
      • Disadvantages
      • Irritation of the gastric mucosa
      • Destruction of some drugs by the gastric acid
      • Variable rate of absorption
      • Slow rate of absorption
    • II. Parenteral ( IV, IM, SC ID)
    • Intravenous
      • Advantages
      • Most rapid and uniform response
      • More predictable response
      • Useful for administering drugs that poorly absorbed by other routes
      • Disadvantages
      • Produces more side effects
      • Drugs can not be withdrawn once injected
    • Sublingual routes
      • Area of absorption : oral mucous membrane
      • Drug is placed under the tongue
      • By- Passed effect
      • Example of drug: Nitroglycerine
    • B. Passage Across Body Membrane
      • Types of Body Membrane
        • Cell membrane
        • Intracellular membrane
        • Blood capillaries
      • Composition
          • Phospholipid (40%)
          • Protein (50-60%
      • Physiochemical properties
          • Lipid solubility
          • Molecular size and shape
          • Degree of ionization
            • pH
            • Pka
    • Types of Passage ( Transport)
      • I. Passive transport
          • Simple diffusion
          • filtration
      • II Specialized transport
          • Active transport
          • Facilitated diffusion
          • Pinocytocis
    • C. Absorption
      • movement of molecules from the site of administration to the blood stream
    • Factors Affecting Absorption
      • Physiochemical factors that affect passage
      • Dosage form (bioavailability)
      • Drug solubility
      • Area of absorbing surface
      • Drug concentration
      • Blood flow
    • D. Distribution
      • Movement of molecules from the blood stream to the different tissues of the body
    • Factors Contributing to the unequal rate of Distribution
      • Plasma protein binding
      • Cellular binding
      • Storage in body fats
      • Blood-Brain Barrier
    • E. Molecular Mechanism of Drug action
      • Receptors
      • Affinity
      • Agonist
      • Antagonist
    • Factors affecting Drug activity
      • Antagonism
      • a. pharmacologic
      • e.g. histamine + antihistamine
      • b. physiologic
      • e.g. diuretics + sympathomimetic amide
      • c. chemical
      • e.g. heparin + protamine
      • 2. Additve effect
      • 3. Potentiation
      • 4. Cummulation
      • 5. Tolerance /tachyphylaxis
      • 6. Variation in drug response
    • Drug Termination
      • Redistribution
      • Excretion (kidney)
      • Amount of drug excreted by the kidney depends on the following process
      • 1. passive tubular diffusion ( reabsorption)
      • 2. active tubular secretion
      • 3. filtration
      • * Metabolism
    • Chapter 3 Adverse Drug Reactions
      • Classification
      • 1. Toxic
      • a. exaggerated effect on target organ
      • b. effects on non target organ (side effect)
      • c. effects on fetal development ( terratogenic)
      • d. local reaction
      • e. drug interactions
      • 2. Allergic reactions
      • 3. Idiosyncrasy
      • 4. Interference in natural defense mechanism