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  1. Pharmacology
    Study of actions, effects, and fate of drugs in body
  2. First pass effect
    • - drugs that are absorbed through GI system pass through liver first before going to the body
    • - refers to how much active drug is left after some is de-activated in liver and sometimes in the stomach/intestines
  3. Pharmacokinetics
    Quantitative descriptions of the time course of drug and drug metabolite concentrations in plasma, tissues, or urine (drug fate or what the body does to the drug)
  4. Lipid/water partition coefficient
    • - ratio of solubility in oil vs. water
    • - A mean for expressing whether a drug is more lipid soluble or more water soluble ---> the higher the number, the more lipid soluble the molecule is
  5. Pharmacodynamics
    • study of drug effects and their mechanism of action
    • the study of what the drugs do to you
  6. Drug action
    • molecular mechanism of action
    • may or may not be known and not observable
  7. Drug effect
    • desired therapeutic effect and teh undesired side effects (SE)
    • usually know and observable
  8. Enteral
    • route of administration thru the GI tract
    • ex: Oral, sublingual, or rectal
  9. Threapeutic window
    plasma concentrations where the drug will give the desired response
  10. Small therapeutic window
    more dangerous drug has a greater chance of having adverse SE
  11. Large therapeutic window
    Less likely the drug is to kill somoene or have toxic SE
  12. Parenteral
    • route of drug administration by any other way except enteral.
    • NOT necessarily injected only
    • ex: IV, inhalation, intranasal, injections, patches, etc...
  13. Minimum effective concentration (MEC)
    • where measurable response starts happening
    • the lowest plasma concentration where you start to see desired effect
    • Above this MEC is toxicity
  14. Blood-brain-barrier
    • endothelial cells of CNS capillaries have tight junctions and no fenestrations
    • lipid soluble drugs can diffuse across endothelial cells and basement membrane while water soluble drugs cannot readily diffuse across
    • some drugs enter the CNS via active transport processes
  15. Free drug
    • drug NOT bound to plasma binding proteins
    • ex: Albumin
  16. Volume of distribution (Vd)
    • hypothetical volume of fluid in which the drug is distributed
    • Total amount of drug in body/plasma concentration
  17. Passive diffusion
    • doesn't need help getting across the barrier, has to be somewhat lipid soluble to do this
    • it's the movement of a molecule down its gradient
  18. Absorption
    from site of administration to plasma
  19. factors that affect the rate and extent of absorption
    Rate of drug dissolution, concentration gradient, blood flow, size of absorbing surface, lipid solubility, pH, drug charge and polarity, and condition of absorbing surface
  20. Distribution pathway
    • site of administration --> plasma --> interstitial space --> intracellular space
    • will redistribute after time back to plasma after enough has gone back out of plasma to switch the concentration gradient
  21. Elimination
    hepatic metabolism (phase I and II, biliary secretion), renal elimination, or throuh your breath, sweat, and tears
  22. Various routes employed for drug administration
    • Enterallly: Oral, sublingual, intravenous injection
    • Parenterally
  23. Reasons for various routes of administration
    • many routes used because different drugs require different methods
    • (can't swallow laughing gas or insulin), time course of action (if you
    • need it quicker you won't use an oral adminstration), drug access (where
    • you need the drug to go, inhale asthma meds), condition of patients
    • (non-compliant is NOT good for daily oral)
  24. Barriers to oral absorption
    • drug must first dissolve and be free in solution
    • most drugs are absorobed in small intesttine more than stomach
    • there is a large surface area to the small intestines and the drug must cross the epithelial cells and capillary walls
  25. Absorption pattern for oral administration
    highly variable among pts, grastric/intestinal pH, gastric emptying time, presence/absence of food, or if durgs are co-administered with other drugs
  26. Advantages of oral Admin.
    Most used route, convenient, safe, drug recall is possible (by throwing up or grastric lavage) and usually INexpensive
  27. Oral Admin: Disadvantages
    • slowly absorbed - 30 min - 1 hour delay
    • highly variable between pts
    • some are inactivated by acids
    • first-pass metabolism by liver happens
    • requires conscious/cooperative pt
    • GI irritation can occur
  28. Sublingual admin: Adv
    • warm and moit
    • high blood flow
    • absorption is rapid
    • NO first-pass effect
  29. Sublingual admin: Disadv.
    Unpleasant taste
  30. IV: Adv
    • NO barriers to absorption
    • rapid onset
    • subsequent control of drug concentration is possible
    • large fluid volumes are possible
  31. IV: Disadv
    • High cost compared to oral admin
    • difficult to administer (need trained personelle)
    • can only be used in in-patients
    • irreversible
    • infection and embolism are possible
  32. IV: subcutaneous injections
    • lower blood flow in SQ region leads to slower drug absorption
    • allows for sustained actions
    • allows for injections of poorly water soluble drugs
    • drawbacks --> uncomfortable, incovenient, potential for injury
    • Sit as a "wad" in SQ slowly releasing drug over time
  33. IV: Intramuscular
    • fairly rapid absorption of WATER soluble drugs
    • time course of absorption is dictated by water solubility of drug and blood flow to site
    • allows for depot preparation where drug is leached out all over time and can provide drug over a month
    • useful in non-compliant pts
    • Painful and inconvenient
  34. membrane structures
    • Phospholipid bilayer --> hydrophobic barrier between two aqueous environments
    • cell membranes do NOT have pores
    • Drugs CANNOT filture thru membranes so they must diffuse thru the phospholipid bilayer
  35. Passive diffusion
    • absorption and penetration into cells is mainly by passive diffusion
    • rate varies directly with concentration gradient
  36. factors of movemnt of drug between bodies
    • concentration gradient
    • drug size
    • drug charge
    • Drug solubility in water and in lipid
    • blood flow
    • condition and area of surface absorption
  37. Drug size
    bigger diffuse less easily than smaller molecules
  38. Drug charge, ionization, polarity, and pH
    • drugs that are charged or higly polar are more soluble in water
    • most drugs are weak acids or bases and exists in solution as both charged and uncharged forms
    • if you increase the pH, you increase the unionized from so more can enter the cell
  39. Hydrophilic drugs
    • repelled by hydrophobic barrier of cell membranes
    • extent of passive diffusion for these drugs is limited and they are therefore poorly and slowly absorbed
    • they are rapidly excreted in urine
  40. Lipophilic drugs
    • hydrophobic
    • pass thru membranes more easily by passive diffusion
    • more completely absorbed and slowly eliminated in urine
  41. Blood flow
    • major factor affecting concentration gradient of drugs throughout the body
    • higher local blood flow maintains steeper concentration gradients and faster rates of drug movement from one compartment into another
  42. Protein binding of drugs
    • albumin is principal binding protein in plasma
    • extent and affinity of drug-protein bindind differs widely
    • these can affect the loading dose and other pharmacokinetic decisions and bound drugs can serve as a resevoir or a buffer for free drugs
  43. Drug-drug interactions result from
    displacement of drugs competing for binding sites on plasma proteins
  44. Fat deposits
    • highly lipid soluble drugs become concentrated in fat cells and to a lesser extent, the brain
    • drugs stored here will redistribute back to the plasma and the concentration gradients change
  45. Redistribution most frequently seen when conditions are met:
    • Drug is highly lipid soluble
    • it is given in IV
    • target is high CO organ, such as the CNS
  46. What terminates the drug effect
    phenomenon of redistribution
  47. Drug
    • any chemical
    • medically, any agent used in tx or prevention of dz, or prevention of pregancy
  48. Drug action
    • drugs cause changes at molecular level by interacting with biological macromolecules
    • drugs have molecular mechanism of action
  49. Dose
    actions and effect of drugs are dose-dependent
  50. Therapeutic window
  51. Routes of Administration
    • Local
    • Enteral
    • Parenteral
  52. Routes of Admin: Local
    • keratinous nature of skin severely limits absorption
    • used to treate dermatological conditions
    • Transdermal patches --> some drugs delivered thru skin patches
    • Abdorption is SLOW and substained --> lipid soluble penetrate skin much more readily than water soluble drugs
  53. Oral Admin: 2 barriers
    • Epithelial cells --> because of tight junctions between cells, drug molecules must diffuse THRU these cells
    • Capillary walls
  54. enteral Admin: rectal
    • a suppository may be used when oral route is infeasible
    • ie. in vomiting patient
  55. Parenteral admin: intra-arterial injections
    used primarily for dx procedure
  56. Body water compartments
    • Plasma compartment
    • Extracellular fluid
    • Total body water
  57. Plasma comparment
    drugs that are very large or that are extensively bound to plasma proteins cannot move thru endothelial fenestrations of capillaries and thus are trapped in plasma compartment
  58. Extracellular fluid
    • drug may be small enough to pass thru endothelial slit junctions, but be very hydrophillic and thus incapable of diffusing into cells
    • drugs such as this ahve a Vd that is the sum of plasma water and the interstitial spaces
  59. Total body water
    • if a drug is small enough to cross into interstium and hydrophobic enough to readily diffuse thru plasma membrane and into intracellular space
    • its Vd may approximate the total body water
    • largest Vd
  60. Redistribution
    • drug molecules are constantly moving
    • after a single dose of a drug has been completely absorbed and distributed ===> concentration of drug in plasma may fall below that of concentration in tissues ==> drug tend to move back out of tissue and into blood along its concentration gradient
  61. Biotransformation
    • enzymatic conversion of parent drug into its metabolites
    • metabolite may be larger or smaller than parent drug
    • metabolite may be less active or more active than parent drug
    • this process may or may not require energy
  62. Major site of biotransformation
    Liver
  63. Absorption, distribution, and Elimination of Drugs Pic
  64. Elimination processes:
    • Hepatic metabolism and biliary secretion
    • Renal elimination
    • Sweat, breath, tears, etc
  65. Conjugation reactions
    • Major pathway for drug biotransformation
    • combine sugar, amino acid, or other residue onto to drug ==> making it larger and more water soluble
    • metabolites are too large to be freely filtered at glomerulus
    • secreted into bile and eliminated with stool
  66. Hepatic metabolism and biliary secretion
    • Conjugation reactions
    • hydrolysis
    • oxidation
    • reduction
  67. Renal elimination
    • many drugs and their metabolites are eliminated in urine
    • This process involves glomerular filtration of plasma, may involve reabsorption and/or secretion in kidney tubules
  68. ADBE
    • Concentration of free drug at its site of action is a fxn of:
    • Absorption
    • Distribution
    • Biotransformation
    • Excretion
    • Involves passage of drugs across biological membranes
  69. Active transport of weak electrolytes
    Important mechanism for passage of some drugs across special cells
  70. Examples of active transport of weak electrolytes
    • Renal tubules
    • choroid plexus
    • Hepatocytes
  71. Equation for Rate of diffusion
    • Rate = kD
    • D - drug concentration
    • k - Rate constant of diffusion
    • Rate is proportion to drug's concentration
  72. Water-soluble molecules
    • Ionized molecules
    • Polar molecules
  73. Lipid soluble molecules
    • nonpolar
    • non-charged
    • hydrophobic
    • lipophilic
  74. Drugs: weak acids or weak bases
    • Most drugs
    • exist in solution simultanenously in ionized and non-ionized form
    • Concentration of each form is determined by drug pKa and solution pH
  75. Acids and bases not affected by pH
    • Strong acids and bases, b/c they are completely dissociated and ionized
    • Weak electrolytes, b/c non-ionized form is highly polar and not much affected by pH
  76. Equilibirium distribution of a weak electrolyte as a fxn of pH: Weak Acid
    Total eq. plasma concentration of WA is HIGHER than intracellular concentration
  77. Equilibirium distribution of a weak electrolyte as a fxn of pH: WB
    Total plasma concentration is LOWER than intracellular concentration
  78. Ionization of drugs with respect to different compartments
  79. Quaternary salts
    • Is permanently charged
    • highly water soluble
    • very poorly absorbed
    • will not readily cross blood-brain barrier
    • rapidly excreted in urine if given IV
  80. Active transport: Anion transport
    important for elimination of penicillins and related antibiotics, salicylates, indomethacin, sulfonamides
  81. Active transport: Cation transport
    • potentially important for elimination of quarternary ganglionic blocking drugs
    • certain neuromuscular blocking drugs
  82. Plasma protein binding affects on doses
    • Binding sites may have to be saturated with loading dose to achieve therapeutic concentration rapidly
    • Resevoir fxn - elimination may be prolonged if there is significant binding
    • Glomerular filtration and renal excretion are affected since bound drug is NOT filtered

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