pharmacokinetics and pharmacodynamics of injected drugs page 1-4

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  1. chirality
    • molecule with a 3 dimensional center characteristic of carbon atom
    • -structural basis of enantiomers
  2. Enantiomers
    mirror images of molecules distinguished by the rotation of polarized light when dissolved in water
  3. right handed enantiomer
  4. left handed enantiomer
    Levo-counter clockwise
  5. racemic mixture
    • one that has equal amounts of left- and right-handed enantiomers of a chiral molecule.
    • -each cancels the effects of polarized light
    • -does not rotate polarized light because cavity of each enantiomer is cancelled by one another
  6. stereochemistry
    study of 3 dimensional molecules
  7. stereo selective enantiomers
    relative difference between enantiomers
  8. stereo specific enantiomers
    • absolute difference between enantiomers
    • -lock and key aspect of enzyme and substrate
  9. enantiomers can produce different effects what is an example with bupivicaine
    • right sided= cardiotoxic effects
    • left sided= (ropivicaine) less cardiotoxic effects
  10. hyperactive
    normal effects even with small doses
  11. hypersensitive
    allergy related effects
  12. hyporeactive
    • tolerance to a drug
    • -requires large doses
  13. tachyphylaxis
    increasing tolerance to a few dose of drug
  14. cellular tolerance
    neuronal adaptation to effect
  15. immunity
    antibody related hyporeaction
  16. idiosyncrasy
    unusual effect regardless of dose
  17. additive effect
    • summative increase in effect
    • -second drug acting with first drug will produce an effect equal to algebraic summation
    • 1+1=2
  18.  antagonist
    • binds but will not activate the receptor to produce a physiologic action.
    • may produce a physiologic consequence
    • -commonly have a higher affinity for a given receptor than agonist.
    • the action of one drug opposes the action of another 1+1=0
  19. what are receptor antagonists commonly used for
    • to prevent an endogenous agonist from stimulating receptor and/or
    • -to reverse the action of a previously administered agonist
  20. competitive antagonism
    • high concentrations of an antagonist will move agonist off of the receptor
    • -reversible- a competitive agonist can be overcome if you add enough agonist.
    • Ex: NM blocking drugs (competitive antagonist) acts to block the normal endogenous agonist Ach from binding to the receptor. Then to reverse neostigmine is given which blocks Ach from being metabolized (thus increasing the amount) and this will compete for its site reversing the NM blocker
  21. agonist
    • drug binds to specific receptor and leads to activation of that receptor
    • -commonly used to mimic the actions of an endogenous chemical or neurotransmitter
    • -have varying degrees of intrinsic activity
    • -produce and effect simply by binding with the receptor
  22. partial agonist/antagonist
    • even at maximally effective concentrations they can not produce full effect.
    • -they are only partially active
    • -in absence of full agonist they stimulate the receptor and produce a partial response (partial agonism)
    • -in the presence of a full agonist they bind the receptor and prevent the full agonist from exerting a full effect (partial antagonism)
  23. noncompetitive antagonism
    • more agonist will not move antagonist
    • even high concentrations of agonist can not overcome antagonist.
    • -Irreversible
  24. synergistic effect
    • the combined effect of two drugs is greater than the algebraic sum of their individual effects
    • 1+1=3
  25. potentiation
    • the enhancement of the action of one drug by a second drug that has no detectable action of its own
    • 1+0=3
  26. Central compartment
    • hypothetical volume
    • highly perfused tissues- lungs, heart, brain, and kidneys
    • receives 75% of CO, and is 10% of body mass
    • IV drugs start here and then redistribute to other compartments, then return here for elimination
  27. Peripheral compartment
    • calculated volume
    • -consists of multiple compartments
    • -less perfused tissue- muscle, fat
    • slower uptake
    • -more or less stored here until concentration equilibrium starts to fall
  28. What affects rate of transfer between compartments (central and peripheral)
    • -age
    • identical doses produce different effects (plasma concentrations)
    • -
  29. What happens to drug in compartments with repeated doses
    • residual drug left in peripheral compartments
    • -cumulative effect in central compartment
    • -calculated by elimination half-time and dosing interval
  30. What are means of elimination that do not depend on organs for clearance
    • Hoffman elimination
    • ester hydrolysis
  31. Induction drugs
    • very lipophilic
    • big doses given
    • propofol losses effect quickly by redistribution
    • works on brain, redistributes to tissues once equilibrium is reached and patient wakes up
  32. Plasma concentration curves the distribution phase is known as what
    • alpha phase
    • starts with IV injection
    • shows distribution to peripheral compartments
  33. Plasma concentration curves the elimination phase is known as what and what is this phase
    • beta
    • follows distribution
    • gradual decrease in plasma concentration due to hepatic and renal elimination
  34. Elimination half time
    TEST ????
    • time for plasma concentration to  decrease 50% during the elimination (beta) phase
    • Test ? said something about after continuous infusion
  35. elimination half time is directly proportional to
    • volume distribution
    • more Vd= longer half time
  36. elimination half time is inversely proportional to
    • clearance
    • more cleared=less half time
  37. volume distribution
    • total amount of drug spread to all compartments
    • -half time is longer if drugs stored in tissue
  38. elimination half time is independent of what
    • dose given
    • b/c starts in elimination phase
    • -after equilibration
    • once it goes through tissues, reaches equilibration, then goes into elimination phase
    • **not very significant, because of a lot of factors
    • **more significant is time to awaken or recovery time.
  39. How many elimination half times are needed to rid the body of 96.9% of drug
  40. Elimination half time
    1= how much cleared
    • 1=50%
    • 2=75%
    • 3=87.5%
    • 4=93.8%
    • 5=96.9
    • 6=98.4
  41. when does equilibration occur
    when accumulation=elimination
  42. context sensitive half time
    • used for elimination of drugs infusions after discontinuation
    • - considers combined effects of distribution (lipid solubility) and clearance (metabolism)  as well as duration of continuous infusion
    • -considers transfer rate between compartments (concentration gradient between compartments)
    • ***still dosnt tell us recovery time
  43. time to recovery
    • how far plasma concentration must decrease for patient to awaken. 
    • -depends on the plasma concentration present when the drug is dc'd
    • -if infusion plasma concentration is just above awakening they will wake up fast with a decreased recovery time.
  44. Effect site equilibration
    • the time it takes for injection of drug to reach site that it will effect (tissues such as brain)
    • Ex: short effect- site equilibration=quick onset

    • Important for dosing intervals- dosing before effect can lead to overdose
    • -dosing can also be effected by redistribution to tissues (propofol)
    • this is dependent on tissue blood flow and CO
    • Ex: decreased CO= decreased tissue perfusion=delayed redistribution
  45. What influences systematic absorption
    • intensity and duration of action
    • -depends on solubility of drug
    • local conditions at entry-GI
    • blood flow to area- subarachnoid injections
    • -surface are of site-transdermal patch
  46. Acidic environment like the stomach favors what type of drugs
    non-ionized lipid soluble drugs
  47. disadvantages of oral administration of drugs
    • GI irritation- emesis
    • Destruction by environment- acid or enzymes or other substances
    • Irregularities of absorption-food
  48. What drug bypasses first pass effect
    iv tylenol
  49. transdermal administration
    • provides sustained therapeutic plasma concentration
    • -low incidence of side effects (small doses)
    • -these drugs take a while to work because it gives you steady state
  50. characteristics of favorable effectiveness of transdermal drugs
    and what are these drugs effected by
    • combined lipid and water soluble
    • -molecular weight < 1000
    • -pH 5-9
    • -absence of histamine releasing effects
    • -daily dose requirements < 10 mg
    • effected by
    • -thickness of skin
    • -chemistry of skin in area of administration
  51. upper (proximal) rectal administration of drugs
    • enter portal circulation
    • first pass effect
  52. lower rectum drug administration
    enter systemic circulation
  53. IV or parenteral administration of drugs
    • only acceptable route in unconscious or uncooperative pt
    • -IV administration is
    • rapid-plasma concentration
    • predictable
    • less irritation of administrations site except propofol
  54. distribution of drug after systemic absorption
    after systemic absorption highly perfused tissures receive a large amount of total dose. As plasma concentration decreases below the highly perfused tissue, drug leaves the tissues to be redistributed to less perfused tissue.  Uptake of drug by tissues is mainly determined by blood flow and if drug can penetrate membrane rapidly. With continuing elimination of a drug the plasma concentration decreases below that in tissue and drug leaves tissues and re-enters circulation. a tissue that accumulates drug acts as a reservoir to maintain the plasma concentration and prolong duration of action.
  55. uptake into lungs
    • -first pass pulmonary uptake
    • -lipophilic drugs can deposit more than 65% of drug into lungs- lidocaine, propofol, narcotics
    • -lungs can act as reservoir for drugs and release them back into systemic circulation.
  56. if the half life of a drug is 20 hours and you give dose of 200mg how many hours to get to 25 mg
    60 hours
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pharmacokinetics and pharmacodynamics of injected drugs page 1-4
2014-01-30 03:21:57

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