Princ. Pharm 3

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Anonymous
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128777
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Princ. Pharm 3
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2012-01-18 18:18:54
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Pharmacology
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Pharmacology
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  1. Why is it useful to be able to predict whether a drug is mainly ionized or mainly non-ionized?
    • so we can predict how it will move in the patient’s body – whether or not it will easily cross cell membranes, how easily it is absorbed or excreted by different routes, what route of administration to use.
  2. How does a non-ionized drug move
    through the body?
    lipophilic - crosses cell membranes easily, is absorbed from the GI tract easily, is absorbed form IM injection more slowly, can get into certain locations that a hydrophilic drug cannot (for example, the CNS).
  3. How does an ionized drug move
    through the body?
    hydrophilic – passes through tissue fluid easily, passes through cell membranes more slowly, is absorbed from IM injection well, is absorbed from the GI tract more slowly.
  4. What three factors determine
    whether a drug is mostly ionized or mostly non-ionized?
    whether the drug is an acidic or an alkaline drug, the environmental pH, and the drug’s pKa.
  5. What is an ion”? What is
    ionization?
    an ion is a charged particle, either positive or negative. ex: Na+. ionization is when a molecule becomes ionized, either by dissociation into ions or by combining with an ion. ex: NaCl à Na+ + Cl-
  6. What is an acid?
    a substance that can give up a H+ - a hydrogen ion.
  7. How do acidic drugs ionize?
    by dissociation – (D is drug, H+ is hydrogen ion) DH à D- + H+
  8. What is an alkali, or a base?
    a substance that can combine with a H+ - a hydrogen ion.
  9. How do alkaline drugs ionize?
    by combination – D + H+ à DH+
  10. What does pH refer to?
    pH is the unit used to measure the acidity or alkalinity of a solution. measures the number of available hydrogen ions.
  11. Which is the same as “basic” – acidic or alkaline?
    alkaline
  12. What is the range of pH? What is chemically neutral pH?
    1-14. pH of 7 is neutral.
  13. What is the approximate pH of a
    normal patient’s arterial blood, venous blood, and tissue fluids?
    arterial – pH 7.43, venous – pH 7.34, tissue ph 7.4
  14. Is pH 2 considered acidic or alkaline? How about pH 7 and pH 13?
    because of the presence of CO2 – when dissolved in water, one of the compounds it forms is carbonic acid.
  15. Is pH 2 considered acidic or alkaline? How about pH 7 and pH 13?
    pH 2 is acidic. pH 7 is neutral. pH 13 is alkaline.
  16. What is the approximate pH of the stomach contents? Why?
    stomach pH is about 2 – due to presence of hydrochloric acid – HCl.
  17. What is the approximate pH of the contents
    of the duodenum? Why?
    duodenum pH is about 6 – HCl from stomach is not quite neutralized yet.
  18. When we say that a drug is mostly
    ionized, we mean that the drug exists in a ratio of ionized to non-ionized molecules, and that more than half of the molecules are ionized. True or false?
    true
  19. What 3 things do we need to know to
    predict whether a drug is mainly ionized or mainly non-ionized?
    • the environmental pH, whether the drug is alkaline or acidic, and the drug’s pKa.
  20. What do we mean by “environmental
    pH”?
    • the pH of the environment in which the drug is located – for example, the environmental pH of venous blood is pH 7.34, and the environmental pH of the stomach lumen is pH 2.
  21. How do we know whether a drug is
    acidic or basic?
    we look it up. if you need to know for testing purposes, I will tell you.
  22. Define pKa.
    dissociation constant. the environmental pH at which a drug exists half in the ionized form and half in the non-ionized form. 1:1 ratio
  23. How do we know a drug’s pKa?
    we look it up. if you need to know for testing purposes, I will tell you.
  24. What happens to an acidic drug as
    its environment becomes more acidic?
    it is “happier”, becomes less ionized, more non-ionized
  25. What happens to a basic drug as its
    environment becomes more acidic?
    it is “unhappy”, becomes more ionized, less non-ionized.
  26. What happens to an acidic drug as
    its environment becomes more alkaline?
    it is “unhappy”, becomes more ionized, less non-ionized.
  27. What happens to a basic drug as its
    environment becomes more alkaline?
    it is “happier”, becomes less ionized, more non-ionized. Remember that “happy = non-ionized” and “unhappy = ionized” is a stupid memory trick, and will not under any circumstances appear on a National Board question.
  28. If an acidic drug with a pKa of 4
    is in an environment with a pH of 7, is it mostly ionized or mostly non-ionized?
    mostly ionized.
  29. If a basic drug with a pKa of 6 is
    in an environment with a pH of 7, is it mostly ionized or mostly non-ionized?
    mostly nonionized.
  30. If an acidic drug with a pKa of 8
    is in an environment with a pH of 2, is it mostly ionized or mostly non-ionized?
    mostly non-ionized
  31. Alkaline drugs have to have a pKa
    over pH 7, and acidic drugs have to have a pKa under ph7. True or false?
    false
  32. What
    is “ion trapping”?
    when a drug passes from one compartment of the body to another compartment with a different pH, it may change from non-ionized to ionized (hydrophilic) form and be temporarily stuck there, because now it cannot pass through cell membranes as easily.
  33. How
    can we use ion trapping?
    we can change the pH of the patient’s urine to trap a toxin there, so it can be excreted.
  34. We accidentally gave a patient an
    overdose of an alkaline drug that is normally excreted in the urine. In order to use ion trapping to help excrete the drug faster, should we alkalinize or acidify the urine, and why?
    we should acidify the urine. This puts the alkaline drug in an acidic environment, it will be “unhappy”, it will ionize, and be mostly hydrophilic and water soluble. The drug will now stay in the watery urine and be less likely to cross the lipid cell membranes of the kidney tubule cells and get back into the patient’s blood.
  35. Which PO dosage form of the same drug will be absorbed from the intestines into the blood faster – a tablet or a solution? Why?
    solution – is already in small particles, does not have to take time to be dissolved and broken up.
  36. What is a sustained-release
    preparation? What is its purpose?
    pill designed to dissolve slowly and make a certain amount of drug available over a period of time. the purpose is to give the pill less often, for convenience, and for a more steady blood concentration.
  37. Where are most drugs usually absorbed from the
    GI tract into the bloodstream – in the stomach or in the small intestines?
    small intestines
  38. What effect does delayed gastric
    motility have on the rate of absorption of a drug, and why? Does this speed up or delay the onset of action of the drug?
    delays absorption – due to the delay in reaching the small intestines, where absorption takes place. delays onset of action.
  39. What effect does delayed or slowed
    down intestinal motility have on the amount of absorption of a drug, and why?
    increases the amount of the drug absorbed – because of the increased time that the drug is in the small intestines.
  40. What effect does increased or
    speeded up intestinal motility have on the amount of absorption of a drug, and why?
    decreases the amount of the drug absorbed – because of the decreased time that the drug is in the small intestines.
  41. What is the first-pass effect?
    drug is absorbed out of intestines into the portal system – the veins draining the intestines into the liver. the liver removes as much of the drug from the blood as it can before sending the blood back into the general circulation.
  42. Does the first-pass effect increase
    or decrease the blood concentration of a drug?
    decrease
  43. If a drug has a major first-pass
    effect, which would be the best way to administer this drug – parenterally or PO?
    parenterally
  44. What
    are 2 forms that repository injections can be prepared in?
    lipophilic, or with larger crystals of drug that take longer to dissolve.
  45. What does tissue perfusion refer
    to?
    the amount of blood flow to the tissue.
  46. Subcutaneous area, muscle, or fat –
    which of these tissues has the most tissue perfusion? The least?
    most – muscle, least – fat.
  47. Which tissue absorbs an injected
    drug faster – muscle or fat?
    muscle
  48. What is vasoconstriction?
    Vasodilation?
    vasoconstriction is when the capillaries become narrower and carry less blood to a tissue. vasodilation is when the capillaries become wider and carry more blood to the tissue.
  49. How does vasoconstriction in a
    tissue affect the rate of absorption of a drug injected into that tissue?
    vasoconstriction causes a decreased rate of absorption.
  50. How does vasodilation in a tissue
    affect the rate of absorption of a drug injected into that tissue?
    vasodilation causes an increased rate of absorption.

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