Pharmacodynamics Flashcards

1
Q

define pharmacokinetics

A
  • the study of absorption, distribution, metabolism and excretion of drugs
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2
Q

define pharmacodynamics

A
  • the study of effects of drugs and their mechanisms of action
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3
Q

define Emax and EC50

A
  • Emax is the maximal response produced by the drug
  • EC50 is the drug concentration that produces 50% of the maximal effect
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4
Q

define spare receptors and how Kd and EC50 are affected

A
  • With spare receptors, it seems that EC50 < Kd
    • this is because of signal amplification with one ligand
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5
Q

define efficacy and potency

A
  • efficacy is the maximum effect a drug can produce (Emax)
  • potency is a measure of the concentration or amount of drug necessary to produce an effect of a given magnitutde
    • EC50 usually used to determine potency
    • potency is less important
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6
Q

describe competitive antagonism

A
  • competitive antagonists bind to the agonist binding site on the receptor
    • shifts the curve to the right
  • high concentrations of agonist can surmount the effect of a given concentration of the antagonist
    • the Emax for the agonist remains the same
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7
Q

describe irreversible competitive antagonism

A
  • a receptor bound by an irreversible antagonist cannot respond to the binding of an agonist
    • this is insurmountable
  • the Emax of the agonist is reduced
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8
Q

describe noncompetitive antagonism/allosteric

A
  • noncompetitive antagonists bind to the receptor at a site different from the agonist binding site
    • insurmountable
  • antagonist binding reduces the action of the agonist
  • Emax is decreased
  • identical graph to irreversible competitive antagonist
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9
Q

describe indirect antagonism

A
  • the antagonist binds to a macromolecule in the pathway that links the receptor to the effect
    • for example: a drug that inhibits PKA blocks the effects of a B-adrenoreceptor agonist
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10
Q

define physiological antagonism

A
  • one drug opposes another drug, but through different receptors
    • epinephrine increases bp and causes bronchodilation
    • histamine decreases bp and causes bronchoconstriction
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11
Q

define chemical antagonism

A
  • a chemical antagonist reacts chemically with an agonist to form an inactive product
    • for example, protamine (positively charged) counteracts the effects of heparin (negatively charged)
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12
Q

describe desensitization/tachyphylaxis

A
  • the effect of a drug gradually dimishes when given continuosly or repeatedly
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13
Q

describe quantal dose-effect curves

A
  • the quantal-dose response relationship plots the fraction of the population that responds to a given dose of drugs as a function of the drug dose
  • the responses are either present or not present
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14
Q

describe the median effective dose (ED50)

A
  • the dose at which 50% of individuals exhibit the specified quantal effect
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15
Q

describe TD50 and LD50

A
  • the dose required to produce a particular toxic effect in 50% of animals is called the median toxic dose (TD50)
  • the dose required to cause death in 50% of animals is called the median lethal dose
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16
Q

definie the therapeutic index

A
  • the ratio of the TD50 to the ED50
  • TI = TD50/ED50
  • TI = LD50/ED50