Drug Action

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Author:
mpope
ID:
106562
Filename:
Drug Action
Updated:
2011-10-19 16:38:06
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Drug Action Chapter
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Chapter 1 - Drug action
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  1. What are the three phases of drug action?
    • Pharmaceutic
    • Pharmacokinetic
    • Pharmacodynamic
  2. exipients
    Inert substances added to a drug to enhance absorption or for other reasons
  3. Who has a more acidic GI tract, an infant or an adult?
    Adult
  4. Rate Limiting
    The time it takes a drug to disintegrate and dissolve or to be ready for absorption.
  5. Why is it important NOTto crush enteric coated or beaded capsules or tablets?
    Crushing will alter PLACE and TIME of absorption.
  6. What are the two most common reasons to take meds with food?
    • Increase absorption
    • Protect GI tract
  7. Discribe the pharmaceutic phase of drug action.
    • Breakdown of med into small enough particles to be dissolved in solution.
  8. Describe the pharmacokinetic phase of drug action.
    • The process of drug movement to achieve drug action:
    • absorption
    • distribution
    • metabolism
    • excretion
  9. What are the three modes of absorption?
    • Passive absorption - Diffusion
    • Active absorption - needs carrier (usually H2O sol)
    • Pinocytosis - cell engulfs drug and carries into cell
  10. What kind of drugs ar absorbed faster?
    Lipid soluble/non-ionized
  11. What factors affect drug absorption?
    • Route
    • GI mucosa
    • First Pass Affect
    • Blood flow
    • pain
    • stress
    • hunger
    • fasting
    • food
    • pH
  12. What is it called when a drug passes through the liver first, after absorption. (via portal vein)
    Hepatic first pass or First pass effect
  13. What are three things that can happen to a drug in the liver?
    • totally metabolized
    • metabolized into something more active
    • no effect
  14. Bioavailability
    The amount (%) of a drug that reaches systemic circulation.
  15. Of the three proteins in the blood which can bind with meds, which is the most important?
    Albumin
  16. What factors affect biovailability?
    • Drug form
    • Route of administration
    • GI mucosa
    • Food
    • Other drugs ie Laxatives affect gastric emptying
    • Changes in liver function
  17. Drug Distribution
    Process by which a drug becomes available to body fluids and tissues.
  18. What happens to drugs in the liver?
    • First Pass Effect: Initial Metabolism
    • Lipid to H20 for excretion
    • Some drugs transformed into active metabolites
  19. What factors affect drug distribution?
    • Blood flow
    • Drug's affinity to tissue
    • Protein binding affect
    • Lipid solubility
  20. What are the degrees of protein binding?
    • Highly Protein Bound - > 89%
    • Moderately Protein Bound - 61-89%
    • Low Protein Bound - < 30%
  21. What should the nurse check to help guard against drug toxicity?
    • ALB
    • protein binding percentage of med
  22. Drug Metabolism
    Breaking down of drugs
  23. Where does drug metabolism occur in the body?
    • Liver (mostly)
    • GI tract
  24. What happens to most drugs in the liver?
    Inactivation by liver enzymes
  25. What is drug half-life (t1/2)?
    Time it takes for 1/2 of drug concentration to be eliminated.
  26. What are 2 main factors that affect drug half-life?
    • Metabolism
    • Elimination
  27. What is a long t1/2?
    > 24 hr
  28. What is a short t1/2?
    4 - 8 hr
  29. How many half-lives does it take to reach a steady state of drug concentration?
    3 - 5
  30. What is the main route of drug elimination?
    • Through the kidneys.
    • Others include bile, lungs, feces, saliva, sweat
  31. How does urine pH affect excretion of drugs?
    • Low pH promotes elim of weak base drugs
    • High pH promotes elim of weak acid drugs
  32. What effect does kidney disease have on drug elimination?
    decr GFR will decr elim (and incr concentration)
  33. What is the most accurate test used to determine renal function?
    Creatinine clearance (CRCL)
  34. What is creatinine?
    • A metabolic byproduct of muscle that is excreted by the kidneys. Compares creatinine with levels in urine with that in blood.
    • 85-135 N
    • < 60 renal impairment
  35. What is Pharmacodynamics?
    The study of drug concentration and its effects on the body.
  36. Onset, Peak, and Duration of Action
    • Onset of action - time to reach min effective conc. (MEC)
    • Peak action - time when drug reaches its max blood conc.
    • Duration of action - Length of time a drug has pharmacologic effect
  37. Where are most drug receptors?
    • Cell mebrane
    • Most are protein, glycoproteins, proteolipids, enzymes
  38. What are the names of the 4 receptor families?
    • Kinase-linked receptors
    • Ligand-gated ion channels
    • G protein-gated ion channels
    • Nuclear receptors
  39. Agonist
    A drug that produces a response
  40. Antagonist
    A drug that blocks a response
  41. Where are cholenergic receptors located and what do they do?
    • Bladder, heart, blood vessels, lungs, eyes
    • A drug that stimulates or blocks the cholenergic receoptors affects ALL anatomic sites of receptor locations
  42. Non-specific drugs
    Drugs that evoke a variety of responses throughout the body.
  43. Non-slective drugs
    Drugs that may act at different receptors
  44. What happens to drugs in the liver?
    • First-Pass Effect: Initial metabolism
    • Lipid to H20 soluble for excretion
    • Some drugs transformed into active metabolites
  45. What are the 4 categories of drug action?
    • Stimulation or depression
    • Replacement
    • Inhibition or kill organisms
    • Irratation
  46. What can incr T1/2 of drugs?
    Liver or renal impairment
  47. Therapeutic Index (TI)
    • Estimates the margin of safety of a drug
    • Low TI - DANGER!
    • Monitor serum levels if low TI.
  48. Therapeutic Range (window)
    Between MEC (min effec. conc.)and MTC (minimum toxic conc.)
  49. What do drug peak levels indicate?
    Rate of absorption
  50. What do trough levels indicate?
    Rate of elimination
  51. When is monitoring peak and trough levels indicated?
    When drugs are given with a narrow TI
  52. Loading Dose
    A large initial dose of drug given to rapidly achieve a MEC in plasma.
  53. Tolerance
    Decr in responsiveness to a drug over time.
  54. Tachyphylaxis
    Rapid decr in reponse to a drug
  55. What % of drugs are taken by mouth?
    80%
  56. What kind of person is most likely to have less gastric acidity?
    Very young and elderly
  57. What are the 4 processes of pharmacokinetiks?
    • Adsorption
    • Distribution
    • Metabolism
    • Elimination
  58. What is enteral admistration?
    via oral or gastric mucosa, small intestine, rectum
  59. Bioavailability
    Amount of drug that reaches circulation
  60. What is the Hepatic First Pass Effect?
    Meds being metabolized before they are able to be distributed. This may produce metabolites equal to, less than or more than original drug.
  61. What are methods of topical administration?
    skin, eyes, ears, nose, lungs
  62. What is parenteral administration?
    Administration of meds by route other that ailmentary canal, IM, IV, SQ
  63. What stomach acidity helps to disintegrate and absorb drugs more rapidly?
    1-2 (low)
  64. What does a nurse need to know about a drug to avoid toxic effects?
    • T1/2
    • protein binding %
    • normal SE
    • Therapeutic Range

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