Dr. Brown Pharmacology Ch 3

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Dr. Brown Pharmacology Ch 3
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Pharmacology chapter 3 Dr. Brown
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  1. Study of how the drug produces its effects on the body
    Pharmacodynamics
  2. Study of how a drug moves into, through, and out of the body
    Pharmacokinetics
  3. The ideal range of drug concentration in the body
    Therapeutic range
  4. Top end of the therapeutic range, above that=toxicity
    Maximum effective concentration
  5. Bottom end of the normal therapeutic range, below that=subtherapeutic
    Minimum effective concentration
  6. What is the goal of drug therapy?
    To maintain the drug within the therapeutic range
  7. What 2 things effect the rate at which a drug leaves the body?
    Metabolism and excretion
  8. 3 things that affect the concentration of a drug in the body
    • 1) Route of administration
    • 2) Dose
    • 3) Dosage interval
  9. Routes of administration
    • 1) Intravenous (IV)
    • 2) Intramuscular (IM)
    • 3) Subcutaneous (SC or SQ)
    • 4) Oral (Per OS)
    • Others: Intra-articular, intraocular and per rectum, intra-peritoneal
  10. Amount of drug administered at one
    Dose 

    Expressed in units of mass: mg, g, gr
  11. Raises the drug concentration in the body more quickly into the therapeutic range, initial drug dose.
    Loading dose
  12. Dose needed to maintain the level of drug at the middle of the threshold range
    Maintenance dose
  13. Time between doses
    Dose interval
  14. Accidental injection of IV drug outside the veins
    Extra-vascular injection/perivascular
  15. Why do we give injections into the veins and not into arteries?
    • By the time an IV drug passes through the heart and lungs and returns to the tissues, it has been well diluted in the blood.
    • An intraarterial injection results in the entire drug being delivered in high concentrations directly to the tissues supplied by that artery
  16. Drug administered in an inhaled gas or mist and is absorbed within the lung airways
    Aerosol administration
  17. Random movement of molecules from an area of high concentration through a semi-permeable membrane. Drug must dissolve in the membrane and doesn't require energy.
    Passive diffusion
  18. Passive transport that requires a carrier molecule and energy
    Facilitated diffusion
  19. Like a pump, moves molecules across the membrane using a specialized carrier and can move against the concentration gradient (low to high). Expends energy either to move the drug molecule or to “reset” the carrier molecule
    Active transport
  20. Cell drinking. Requires cellular energy, the cell membrane physically engulfs the molecule and brings it into the cell
    Pinocytosis
  21. If it requires a carrier molecule and all of the molecules are occupied, the transport system is called ____. The system is operating at its _________.
    • Saturated 
    • Transport maximum (t-max)
  22. Cell eating, requires cellular energyand the cell membrane physically engulfs the molecule and brings it into the cell
    Phagocytosis
  23. Passive diffusion rates are related to....
    • The concentration gradient
    • Drug molecule size
    • Nature of the drug- reflects its ability to dissolve in the phospholipid cell membrane
    • Temperature of the environment
    • Thickness of the membrane
  24. Factors for faster diffusion...
    • Large concentration gradient
    • Small, lipophilic molecule
    • If the temperature at the cell membrane is increased
    • The membrane is thin
  25. Hydrophilic
    • Water loving, also known as lipophobic (fat-fearing)
    • Usually polarized (contain charges at the end of the molecule) or ionized (the molecule has a net positive or negative drug
  26. Lipophilic drug
    Fat loving, nonpolarized or non-ionized
  27. Where is a lipophilic drug most likely to be found?
    Acidic environment of the stomach
  28. Where is a hydrophilic drug most likely to be found?
    Alkaline environment of the intestines
  29. 4 steps in drug movement
    • 1) Absorption
    • 2) Distribution
    • 3) Metabolism
    • 4) Excretion
  30. What alters 4 steps in drug movement?
    Disease or physiologic conditions
  31. Movement of drug molecules from the site of administration to the systemic circulation
    Drug absorption
  32. Drugs not designed to be totally absorbed
    • Local anesthetics
    • Topical insecticides (flea powder)
    • Topical antibiotics
    • Drugs that are intended to work within the lumen of the intestine
  33. Degree to which an administered drug is absorbed.
    Bioavailability

    Represented by the letter F
  34. IM and SQ drugs need to dissolve in the extracellular fluid to reach the capillaries, which drug form will be absorbed best?
    Hydrophilic form will be absorbed best. Some are purposely made lipophilic to delay absorption over several days after injection
  35. Routes of administration and their bioavailability fastest to slowest
    • IV
    • IM
    • SQ
    • PO
  36. PO drugs need to pass through the cell membranes of the intestinal tract, which drug form will be best absorbed?
    Lipophilic will be absorbed better. Hydrophilic drugs are poorly absorbed from the gut and remain in the intestinal tract to be expelled with the feces
  37. Aspirin example in regards to pH ratio
    • In the stomach, acidic, pH2
    • Aspirin exists as a 1:10 ratio, 1 hydrophilic (ionized) molecule per 10 lipophilic (nonionized) molecules

    In the duodenum, pH 6 Aspirin shifts to its hydrophilic form with 1000 hydrophilic molecules per 1 lipophilic molecule

    Since lipophilic molecules are required to diffuse across cell membranes, aspirin is more readily absorbed in the stomach than the small intestine
  38. The pH where the drug has an equal ratio (1:1) of ionized to nonionized molecules
    pKa
  39. pKa example
    For any acid drug with a pKa of 7, the ratio of ionized to nonionized molecules is 1:1 at a pH of 7
  40. Movement of a drug molecule into a compartment where it changes from a lipophilic state to a hydrophilic state and remains in that compartment
    Ion trapping
  41. pH of the stomach, duodenum and body fluids
    • Stomach 1-3
    • Duodenum 6-7
    • Within cells and most body fluids, fairly constant 7.4
  42. Aspirin example in regards to ion trapping
    • Aspirin taken by mouth
    • Acidic environment of stomach, it is nonionized and crosses cell membranes
    • Inside the cells, it shifts to ionized form and is trapped within the cell
    • Aspirin molecules can accumulate within the cells in the lining of the stomach and result in a slower absorption of the drug
  43. Benefits of ion trapping in regards to the kidneys
    • Used to remove excessive drugs through the kidneys
    • Drug molecules are filtered out of the blood by the kidneys, but in their lipophilic state, they can be reabsorbed back into the systemic circulation
  44. Benefits of on trapping in regards to urine
    • If the pH of the urine can be changed, the drug or toxin molecule can be changed to its ionized form (hydrophilic)
    • These hydrophilic molecules cannot diffuse across the renal tubulular cell membranes to be reabsorbed back into the body
    • The change in urine pH by urinary acidifiers or alkalizers can trap the molecule within the lumen of the renal tubule and allow it to be safely excreted form the body
  45. Dissolving of drugs from their tablet from into smaller particles and allow them to be absorbed
    Dissolution
  46. Stomach contractions that mix stomach contents and move them to the small intestine
    Gastric motility
  47. The mixing and propulsive contractions of the small intestine
    Intestinal motility
  48. How does decreased and increased gastric motility affect drug absorption
    • Decreased gastric motility can delay onset of orally administered drugs
    • Increased gastric motility can allow the drug to reach the small intestine sooner
  49. How can diarrhea and constipation affect drug absorption
    Hypermotile diarrhea- the drug is moved past the small intestine before it is full absorbed and it is passed in the feces

    Constipation or anti-diarrheal drugs may result in complete absorption of a drug that is not meant to be full absorbed
  50. The phenomenon by which the liver removes so much of the drug that little reaches the systemic circulation
    First pass effect
  51. What does the hepatic portal system do in regards to drugs?
    Blood from the intestines must pass through the liver where potential toxins are removed
  52. The extent to which a tissue is supplied with blood
    Perfusion
  53. Which has better tissue perfusion, muscle or SQ?
    Muscle
  54. What can effect tissue perfusion?
    • Changes in temperature
    • Vasoconstriction of skin when its cold 
    • Vasodilation of muscles with fight or flight
  55. The movement of drugs from the systemic circulation into tissues
    Distribution
  56. Distribution of drugs occurs through small gaps in capillary walls called _______.
    Fenestrations
  57. Barriers to drug distribution
    • Blood brain barrier
    • Placenta
    • Prostate
    • Globe of the eye
  58. Well perfused tissues
    • Exercised skeletal muscle
    • Liver
    • Kidneys
    • Brain
  59. Poor perfused tissues
    • Inactive skeletal muscle
    • Fat 
    • Tendons
    • Ligaments
  60. The movement of drug from the blood, to the first tissue, back to the blood and into a second tissue
    Redistribution
  61. Plasma contains _____ and ____ and other proteins that bind to specific hormones and compounds in the body
    • Albumin
    • Globulins
  62. Only the ____ of the drug molecule is small enough to distribute through the capillary fenestrations
    Free form
  63. Take the amount of drug given and the resulting concentration in the body and you can calculate what?
    Volume of distribution
  64. A _____ volume of distribution means the more tissues that the drug is able to penetrate
    Larger
  65. What cellular changes can occur when a drug molecule binds with a receptor?
    • Producing secretions
    • Contracting muscle cells
    • Depolarizing neurons
  66. A drug that binds to the receptor and produces an effect on the cell
    Agonist
  67. Reverses the effects of an agonist
    Antagonist
  68. Physically combine with ions or other compounds to produce their effect
    Chelators
  69. What combines with lead in the body and facilitates the excretion of the combined product in the urine
    Penicillamine
  70. What combines with calcium in a blood sample and prevents the clotting mechanism from turning the blood sample into a clot
    EDTA
  71. What combines with the strong hydrochloric acid in the stomach to form a much weaker acid thereby reducing stomach irritation
    Antacid drugs
  72. The process by which drugs are altered by the enzymes and chemical reactions in the body before they are eliminated (drug metabolism)
    Biotransformation
  73. Altered drug molecule is called what
    Metabolite
  74. The majority of enzymes involved in biotransformation are in which organ?
    Liver
  75. Other places biotranformation can occur besides the liver...
    • Skin
    • Intestinal tract
    • Lungs
  76. Phase 1 of biotransformation
    • Chemical process of reduction, oxidation, or hydrolysis
    • Sometimes phase I does not diminish the activity of a drug
    • Drugs that require biotransformation to become active are “prodrugs”
    • Example: prednisone is biotransformed by liver enzymes to its active anti-inflammatory metabolite form, prednisolone
  77. Phase 2 of biotransformation
    • Conjugation
    • The metabolite is combined with another molecule such as glucuronic acid, sulfate, or glycine
    • The conjugated molecule is usually more water soluble (hydrophilic) and more easily excreted into the urine
  78. Repeated exposure of a drug results in an increased biotransformation of these dugs “induced metabolism” and other drugs that use that system
    Mixed function oxidase system
  79. The seemingly shorter duration of effect of the drug after it’s metabolism has been induced from repeated exposure
    Tolerance
  80. What can decrease the chances of a drug undergoing biotransformation
    • Species
    • Young animals
    • Old animals
  81. Movement of drug molecules out of the body
    Elimination
  82. 2 major routes of drug elimination
    • Kidneys out in the urine
    • Liver into bile and out in feces
  83. Other ways drugs are eliminated from the body
    • Lungs
    • Saliva
    • Milk
    • Sweat
  84. Renal elimination
    • Filtration through glomerulus
    • Active secretion through the proximal convoluted tubule
    • Possible reabsorption, some molecules may move back into circulation from the loop of Henle
    • Must be in lipophilic form
  85. Things that effect renal excretion
    • Hypoalbuminemia or hypoproteinemia
    • Lowered blood pressure
    • Dehydration
    • Blood loss
    • Shock
    • Increased sympathetic tone 
    • IV fluids
  86. Hepatic elimination
    • Drugs move by passive diffusion into the hepatocytes then are secreted directly into the bile or are metabolized and then secreted into bile
    • If secreted in lipophilic form, the drug can be reabsorbed across the intestinal wall transported back to the liver by the hepatic portal system. This is called “enterohepatic circulation”
  87. The time it takes for the drug concentration to be reduced by 50%
    Half life
  88. When a drug is given repeatedly, it accumulates to a point at which the highest and lowest concentrations are the same
    Steady state
  89. The time from the beginning of therapy to reach steady state is equal to __ times the half life
    5
  90. The time after drug administration during which the animal cannot be sent to market for slaughter and the milk and eggs must be discarded, based on the elimination half-life of the drug
    Drug withdrawal time
  91. In a dosage regimen, the instructions "b.i.d" would be what component?
    Dosage interval
  92. Form of a drug molecule that cannot readily penetrate a cell membrane
    Hydrophilic or ionized
  93. Type of drug (not drug molecule form) that becomes more ionized as the environmental pH becomes more acidic
    Alkaline or basic drug
  94. Movement of a drug from the blood into the brain would be an examaple of this movement of drugs in pharmacokinetics
    Distribution
  95. Movement of drug from the intestinal tract, to the liver, to the blood and tissue, back to the liver, to the intestinal tract, and then reabsorbed back from the GI tract to the liver
    Enterohepatic circulation
  96. Route of administration in which a drug is injected into the layers of the skin
    Intradermal
  97. A. 100 mg of drug administered, bioavailability 0.7
    B. 150 mg of drug administered, BA 0.5
    C. 200 mg of drug administered, BA 0.4
    D. 250 mg of drug administered, BA 0.2

    Which drugs is absorbed in the greatest amount?
    C
  98. Drug A is an acidic drug, is it more likely to be in lipophilic or hydrophilic form when placed in an acidic environment?
    Lipophilic
  99. With acid drugs if the pKa is lower than the pH of the liquid its in then its in which form?
    Ionized
  100. With acid drugs if the pKa is higher than the pH of the liquid its in then its in which form?
    Nonionized
  101. With alkaline drugs is the pKa is lower than the pH of the liquid its in then its in which form?
    Nonionized
  102. With alkaline drugs is the pKa is higher than the pH of the liquid its in then its in which form?
    Ionized
  103. Rank the following drugs in order from 1 to 4, with 1 being the most rapidly absorbed and 4 being the slowest to be absorbed from a SQ tissue site with a pH of 7.4
    • Basic drug, pKa of 5.4   (4) 
    • Acid drug, pKa of 8.4    (3)
    • Acid drug, pKa of 6.4    (2)
    • Basic drug, pKa of 9.4  (1)
  104. If the half life for a drug is extended should you increase or decrease the dose?
    Decrease dose
  105. If the metabolism of a drug has been accelerated by exposure to phenobarbital should the dose be increased or decreased
    Increase dose
  106. A hypoproteinemic animal is given a drug that is normally highly protein bound should the dose be increased or decreased?
    Decrease dose
  107. The volume of distribution for a drug is decreased should the dose be increased or decreased
    Decrease dose
  108. TRUE OR FALSE. If the metabolism of a drug has been induced, the dose of the drug should be decreased to compensate?
    False
  109. TRUE OR FALSE. Excretion of a drug by the liver is called biliary excretion
    True
  110. TRUE OR FALSE. The neutralization of stomach acid by tums or rolaids is a non-receptor mediated action
    True
  111. TRUE OR FALSE. An agonist would typically have little or no intrinsic activity on a receptor to which it binds
    False
  112. TRUE OR FALSE. If the Vd of a drug increases the concentration of the drug decreases
    True

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