Lec 1& 2


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Lec 1& 2

  1. 1. Please, shut down your mobile<br />
  2. 2. Faculty of Pharmacy<br />Department of Pharmacology<br />pharmacology<br />General Pharmacology<br />3rd year pharmacy students<br />By <br />“Dr. Shimaa Elshazly”<br />
  3. 3. What is pharmacology?<br />The term pharmacology comes from the Greek words:<br />•Pharmakon- drug or medicine<br />•Logos- the truth about or a rational discussion<br /> …………Truth about medicine<br />• Pharmacology is the study of how<br />drugs exert their effects on living<br />systems.<br />• More specifically it is the study of<br />the interactions between a living<br />organism and drugs that alter normal<br />biochemical function.<br />
  4. 4. History of Pharmacology<br />Early pharmacology<br />focused on natural<br />substances, mainly plant<br />extracts.<br />
  5. 5. Modern approach<br /><ul><li> Pharmacology is a discipline as a bridge, not only to connect pharmacy with medicine, but also to link foundational medicine to clinical medicine</li></ul>Foundational Medicine<br />Clinical Medicine<br />Pharmacology<br />Medicine<br />Pharmacy<br />Manufacture of Drugs<br />Research of Drugs<br />
  6. 6. ……..Subdivisions of Pharmacology<br /><ul><li>Clinical Pharmacology:</li></ul>application of pharmacodynamics and pharmacokinetics to human.<br />•Toxicology -Study of<br />harmful effects of drug<br />•Posology- How medicines are<br />dosed or calculation of dose<br />•Pharmacognosy-<br />Development of medicinal<br />substances obtained from<br />plants<br />
  7. 7. Division of Pharmacology:<br /><ul><li>The science of pharmacology is divided into TWO important and interrelated areas : </li></ul>Pharmacokinetics: Study of the absorption,<br />distribution, metabolism and excretion of drugs<br />(ADME).<br />……………..what the body does to the drug<br />B. Pharmacodynamics: Study of the molecular,<br />biochemical and physiology effects of drugs on<br />cellular systems and their mechanisms of action.<br />……………..what the drug does to the body<br />
  8. 8. What Is a Drug?<br /><ul><li> A drug is a substance which when given to a patient can affect his body functions. This effect is useful in the treatment of a disease ( therapeutic ).If given in high dose it may cause a disease due to the toxicity of the drug itself. </li></ul>In other meaning:<br /><ul><li>Chemical agents used in the diagnosis, treatment, or prevention of disease</li></li></ul><li>What are the sources of a drug?<br />1- Natural<br />2- Semisynthetic<br />3- Purely synthetic<br />4.Mineral Origin<br />5.Genetic Engineering<br />
  9. 9. 1- Natural: <br />Plant Origin: eg.Atropine from belladonna & Morphine from Opium. <br />b) Animal Origin: eg. Insulin, calcitonin etc. <br />2- Semisynthetic:<br /><ul><li> These are compounds that are obtained from natural source and subjected to chemical modification eg.Penicillins and heroin (prepared by acetylation of morphine). </li></ul>3- Purely synthetic:<br /><ul><li> Are purely chemically synthesized. eg. The majority of drugs. </li></li></ul><li>4.Mineral Origin:<br />eg. Iodine, magnesium sulphate <br />5.Genetic Engineering:<br />a) Gene Therapy. <br />b) Recombinant DNA as the production of human insulin from bacterial origin. <br />
  10. 10. Pharmacokinetics of drugs<br />(ADME)<br />……………..what the body does to the drug<br />Are studies of: <br /><ul><li>Absorption
  11. 11. Distribution or Disposition
  12. 12. Metabolism
  13. 13. Excretion or Eliminationof drugs</li></li></ul><li>
  14. 14.
  15. 15. Drug Absorption<br />• Absorption is the movement of a drug from its site of application into the blood or lymphatic system without being chemically altered<br />• Mathematically it is define in terms of Bioavailability (Rate<br />and extent of absorption).<br />
  16. 16. Bioavailability<br />Definition: Rate and extent of absorption <br />i.e. Ka (Absorption constant)………. Rate of absorption. <br />Area under curve (AUC)………. extent of absorption.<br />• for i.v.: 100%<br />• for non i.v.: ranges from 0-100%<br />e.g. lidocaine bioavailability is 35% due to destruction in gastric acid and liver metabolism<br />
  17. 17. Process of Absorption<br />In order for a drug to be absorbed, it must be able to<br />pass through cell membranes (which is a lipid<br />barrier)<br />• Lipid soluble drugs would be ideal to pass through the<br />membrane easily.<br />• Drugs can be absorbed by 4 main ways :<br />1. Simple diffusion = passive diffusion.<br /> 2. Active transport.<br /> 3. Facilitated diffusion.<br /> 4. Pinocytosis (Endocytosis).<br />
  18. 18. Cell membrane<br />
  19. 19.
  20. 20. Simple or passive diffusion<br /><ul><li> Water soluble drug (ionized or polar) is readily absorbed via aqueous channels or pores in cell membrane.
  21. 21. Lipid soluble drug (nonionized or non polar) is readily absorbed via cell membrane itself.</li></li></ul><li>
  22. 22. Simple diffusion<br />Characters<br /><ul><li>common.
  23. 23. Occurs along concentration gradient. Non selective
  24. 24. Not saturable
  25. 25. Requires no energy
  26. 26. No carrier is needed
  27. 27. Depends on lipid solubility.</li></li></ul><li>Simple diffusion<br />Low conc<br />High conc<br />
  28. 28. Simple diffusion<br />Drugs exist in two forms ionized (water soluble) & nonionized forms (lipid soluble) in equilibrium.<br />Drug ionized + nonionized<br /> Only nonionized form is absorbable.<br />
  29. 29. Six things influence the rateof diffusion<br /><ul><li>Concentration gradientBig concentration difference (Fick’s Law) increasediffusion.
  30. 30. Size of molecule involved Large molecules slowdiffusion
  31. 31. Distance the molecule has to travelShort distance increase diffusion
  32. 32. TemperatureHigh temperatures increasediffusion
  33. 33. Solubility of the molecule
  34. 34. Surface area of the membrane over which the molecule can work.Large surface area increase diffusion</li></li></ul><li>Active Transport<br /><ul><li> Relatively unusual.
  35. 35. Occurs against concentration gradient.
  36. 36. Requires carrier and energy.
  37. 37. Specific
  38. 38. Saturable.
  39. 39. Iron absorption.
  40. 40. Uptake of levodopa by brain.</li></li></ul><li>
  41. 41. Carrier-mediated Facilitated Diffusion<br /><ul><li>Occurs along concentration gradient.
  42. 42. Requires carriers
  43. 43. Selective.
  44. 44. Saturable.
  45. 45. No energy is required.
  46. 46. Selection is by size; shape; charge.
  47. 47. Common molecules entering/leaving cells this way include glucose and amino-acids. </li></li></ul><li>
  48. 48.
  49. 49.
  50. 50.
  51. 51.
  52. 52. Phagocytosis (Endocytosis & Exocytosis)<br />Endocytosis: uptake of membrane-bound particles. <br />Exocytosis: expulsion of membrane-bound particles. <br />High molecular weight drugs or <br />Highly lipid insoluble drugs<br />
  53. 53. Factors which influence the rate of absorption:<br />– Routes of drug administration<br />– The physicochemical properties of the drug<br />– Dosage forms<br />– Circulation at the site of absorption<br />– Concentration of the drug<br />
  54. 54. Routes of drug administration<br />Enteral <br />via gastrointestinal tract (GIT).<br />Oral <br />Sublingual<br />Rectal <br />Parenteral administration = injections.<br />Topical application<br />Inhalation<br />
  55. 55. Oral administration<br />
  56. 56. First pass Metabolism<br />Metabolism of drug in the gut wall or portal<br />circulation before reaching systemic circulation<br />So the amount reaching system circulation is less than the amount absorbed<br />Where ?<br /><ul><li> Liver
  57. 57. Gut wall
  58. 58. Gut Lumen</li></ul>Result ?<br /><ul><li> Low bioavailability.
  59. 59. Short duration of action (t ½).</li></li></ul><li>First pass effect<br />
  60. 60. Dosage forms<br /> Capsules<br /> Tablets<br /> Syrup<br /> Suspension<br />Hard- gelatin capsule<br />Soft- gelatin capsule<br />Tablets<br />Spansule<br />
  61. 61. Sublingual <br />
  62. 62. Rectal administration<br />
  63. 63. Parenteral administration<br />Intradermal (I.D.) (into skin)<br />Subcutaneous (S.C.)<br />Intramuscular (I.M.)<br />Intravenous (I.V.) (into veins)<br />Intra-arterial (I.A.) (into arteries)<br />Intrathecal (I.T.) (cerebrospinal fluids )<br />Intraperitoneal (I.P.) (peritoneal cavity)<br />Intra - articular (Synovial fluids)<br />Intracardial<br />
  64. 64.
  65. 65. Parenteral administration<br />
  66. 66. Ampoule Vial<br />
  67. 67. 1- Intravenous ( IV )<br /><ul><li> The drug is injected right into the venous blood.</li></ul>Advantages:<br /><ul><li> Immediate effect.
  68. 68. Suitable for drugs not absorbed by the gut.
  69. 69. Rapidly destroyed drugs, short t½ can be infused continuously to provide a steady state of plasma concentration</li></ul>Disadvantages:<br /><ul><li> Dangerous if given rapidly.
  70. 70. Prolonged infusion of irritant drugs lead to venous thrombosis.
  71. 71. Susceptibility to infection if not using aseptic conditions. </li></li></ul><li>2- Intramuscular<br /><ul><li> Injection is made into a large muscle </li></ul>Advantages:<br /><ul><li> Reliable & produces more rapid absorption than SC.
  72. 72. Could be used for irritant drugs.
  73. 73. Could be used for depot preparations eg. Long actingpenicillins.</li></ul>Disadvantages:<br /><ul><li> It is painful.
  74. 74. Not accepted as self administration.
  75. 75. Risk of infection & formation of abscess.</li></li></ul><li>3- Subcutaneous (SC)<br />Just under the skin<br />Advantages<br /><ul><li> Can be given by the patient
  76. 76. Slow to obtain sustained drug effect eg. Insulin but generally complete
  77. 77. Suitable only for nonirritant drugs.</li></ul>Disadvantages<br /><ul><li> Large volume may be painful.
  78. 78. Tissue damage from irritant drugs
  79. 79. Maximum of 2 ml injection
  80. 80. Heat, Vasoconstrictors such as adrenaline greatly decrease the rate of absorption. </li></li></ul><li>Produce local effect to: <br /><ul><li>Skin (percutaneous) e.g. allergy testing, topical local anesthesia
  81. 81. Mucous membrane of respiratory tract (Inhalation) e.g. asthma
  82. 82. Eye drops e.g. conjunctivitis
  83. 83. Ear drops e.g. otitis externa
  84. 84. Intranasal, e.g. decongestant nasal spray</li></ul>Topical application<br />
  85. 85. Inhalation<br />
  86. 86. Nebulizer Atomizer<br />
  87. 87. Transdermal delivery system (TDS) <br />TDS is a method by which the drug is released<br />and absorbed through the skin for systemic<br />absorption by a medicated adhesive patch<br />applied to skin <br />* Slow effect (prolonged drug action)<br /> e.g. the nicotine patches <br />Advantages: <br /><ul><li> Lead to more stable drug level in the blood.
  88. 88. Avoid inactivation by first hepatic bypass eg. Nitroglycerine
  89. 89. Minimal side effects. </li></li></ul><li>Factors which influence the rate of absorption:<br />– Routes of drug administration<br />–The physicochemical properties of the drug<br />– Dosage forms<br />– Circulation at the site of absorption<br />– Concentration of the drug<br />
  90. 90. Factor affecting absorption……<br />Physico-chemical properties of drug<br /><ul><li> Molecular weight</li></ul>· Drugs with a small M.W. are absorbed well<br />· Drugs which are large (often proteins) are absorbed poorly.<br /><ul><li> Chemical and enzymatic stability</li></ul>· The drug should be stable in gastric acid and in gut enzymes.<br />e.g. Penicillin G is highly acid labile, or unstable in acid.<br /><ul><li> Aqueous and lipid solubility</li></ul>· For better absorption a drug must have optimum water and lipid solubility or a optimum partition coefficient. If it is highly lipid soluble it would not dissociate in the circulation i.e. Ion trapping. On the other hand, if it is highly water soluble then it will not cross the biological membrane.<br />
  91. 91. Factor affecting absorption……<br />pH and lipid solubility:<br />Most drugs are either weak acids or weak bases and can exist in <br />either the ionised (less lipid soluble) or unionised (more lipid <br />soluble) form depending on the pH of the surrounding environment.<br />REMEMBER THAT A DRUG IS ABSORBED BETTER IN THE<br />UNIONISED FORM (Lipophillic drug can cross cell membrane)<br />
  92. 92. Ion Trapping<br />Body fluids where a pH difference will favor trapping of highly<br />lipophillic drugs: e.g. Breast milk , Aqueous humor (eye) ,<br />Vaginal secretions , Prostatic secretions<br /><ul><li>Aspirin is an acidic drug (pKa=5) and exist in the unionised form in stomach (pH 2.0)
  93. 93. In this form, it can enter the cells of the stomach lining (pH=7.4) where it is ionized and, in this form, it cannot leave the cell.
  94. 94. The concentration of ionized aspirin inside the cell continues to rise until it saturates and precipitates as crystals, which lead to gastric bleeding.</li></li></ul><li>Factors which influence the rate of absorption:<br />– Routes of drug administration<br />– The physicochemical properties of the drug<br />– Dosage forms<br />– Circulation at the site of absorption<br />– Concentration of the drug<br />
  95. 95. Drug dosage forms<br /><ul><li>Different dosage forms have different rate and extent of absorption.
  96. 96. A syrup has fast rate of absorption as compare to tablet
  97. 97. A capsule has fast rate of absorption than tablet
  98. 98. Controlled-release, timed-release, sustained-release dosage form have a uniform absorption and less side effects</li></li></ul><li>Thank you <br />