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Anesthesia Pharm > Pharmacodynamics > Flashcards

Pharmacodynamics Flashcards

1
Q

Primary mechanism of action of IV and inhaled anesthetics?

A

Potentiating of inhibitory GABA receptors

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2
Q

Who is Paul Ehrlich?

A

Introduced the concept of receptors to explain things that were perplexing

  • Antibody/antigen interactions and poisons
  • Agents do not act unless they are bound
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3
Q

Who is L.N. Langley?

A

Utilities the term “receptive Substance” to explain the effects he observed
- Nicotine caused muscle tissue to contract
- Effect could be reversed by Clare
Muscle still responsive to electrical stimulation

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4
Q

Who is Ahlquist?

A

Determined that receptor subtypes to explain why adrenergic receptors results in the contraction of some tissues and relaxation of others

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5
Q

what is a receptor?

A

A protein or other substance that binds to an endogenous chemical(drug). The coupling produces a cascade of events.

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6
Q

What are 3 properties of receptors?

A
  • specificity
  • selectivity
  • sensitivity
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7
Q

What are the 7 different receptors?

A
  • 7 transmembrane receptors
  • Ligand gated ion channels
  • Ion channels
  • Catalytic receptors
  • Nuclear receptors
  • Transporters
  • Enzymes
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8
Q

What is the most important receptor in anesthesia?

A

Acetylcholine receptor

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9
Q

What is necessary for acetylcholine receptors to open?

A

Binding of a chemical messenger as well as the endogenous agonist acetylcholine

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10
Q

What are agonists of acetylcholine channels?

A

Nicotine
Probationers
Choline

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11
Q

What happens when agonists bind to an acetylcholine receptor?

A

All present subunits undergo a conformational change and the channel is opened into the cell

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12
Q

Where are drug receptor proteins located?

A
  • Luminal membrane
  • Surface of the ionic Chanel
  • intracellular sties
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13
Q

What are intracellular sites of drug receptor proteins?

A

When the drug passes into the cell and acts on receptors once inside the cell

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14
Q

what are the main bonding forces that aid in drug/receptor binding?

A

Van der wall forces

Ionic bonding

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15
Q

What is the process by which a cell converts on type of signal into another?

A

Second messenger pathway

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16
Q

What do second messengers regulate?

A

Enzymes (protein kinases, phosphates) that drive intracellular actions

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17
Q

How do inhalation anesthetics bind to cell receptors?

A

By a nonspecific hydrophobic bonding mechanism

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18
Q

Endogenous proteins provide alternative drug binding sites - what is this important for?

A

Duration of action of a drug
Acceptors reduce the amount of unbound drug available for receptor completing
I.E. Albumin - primary receptor and bind to acidic drugs making them unavailable to bind to receptors. Also acts as a resin ore to increase duration of action of the drug

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19
Q

What is the drug-receptor response equation?

A

D + R (DCR) TF

Drug + receptor are in equilibrium with a drug receptor complex which is in equilibrium with a tissue response.

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20
Q

When is tissue effect seen from drug/receptor interactions?

A

When sufficient receptors have been occupied and activated by the free drug

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21
Q

What happens when a drug attaches to a receptor?

A

A conformational shift takes place in that protein receptor.

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22
Q

Of what importance is the conformational shift when a drug binds to a receptors?

A

Without the shift, no tissue response will occur

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23
Q

what happens to the steady state levels of IV and inhalation drugs as age increases?

A

Decreases

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24
Q

What is the meaning of pharmacodynamics?

A

What the drug does in the body

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25
Q

what is an agonist?

A

Substance that binds to a specific receptor and triggers a response in that cell. It mimics the action of endogenous substance that binds to the same receptor

26
Q

What is an antagonist?

A

Drug that has affinity for the receptor but does not activate the receptor to produce a physiologic response.

27
Q

Does an antagonist or agonist have higher affinity for a receptor?

A

Antagonist

28
Q

What is affinity/potency?

A

Used to differentiate between agonists that activate the same receptor and can all produce the same response but at differing concentrations

Most potent drug require is the lowest dose

29
Q

What is the efficacy?

A

Ability of a drug to produce the desired response expected by stimulation of a given receptor population.

Refers to the max possible effect that can be achieved by the drug

30
Q

What is intrinsic activity?

A

Relative maximal effect obtained when comparing compounds in a series - morphine, dilaudid, Demerol

31
Q

what is a partial agonist?

A

Activates receptor but cannot produce a maximal response. May also be able to partially block the effects of full agonists

Ex. Nubane

32
Q

What is an inverse agonist?

A

Binds to receptor and results in the opposit effects that one would expect

33
Q

What is the spare receptor concept?

A

Describes an over abundance of receptors that act as a physiologic cushion

34
Q

What is the quantal drug response?

A

Use of drug response curves - action of drug can be quantified and expressed as the effective dose 50, the toxic dose 50, and lethal dose 50

35
Q

What is the therapeutic dose index?

A

Ratio of lethal dose 50 to effective dose 50

36
Q

What is a ligand?

A

Molecule that is able to bind to and form a complex with a receptor to produce a response

37
Q

What is receptor adaptation or homeostasis?

A

Number and activity of receptor population that can increase or decrease in response to chronic drug administration

38
Q

What is up regulation of receptors?

A

A process by which the cell increases the number of receptors of a given drug

39
Q

What is down regulation?

A

Process by which a cell decreases the receptors for a given drug in response to chronic stimulation.

40
Q

What is the linear dose response curve?

A

Characterizes the change in measured response as an administered dose is increase

41
Q

In the linear dose response curve, where does the greatest change occur?

A

Left hand side - hyperbolic state

42
Q

What is the log-rhythmic scale?

A

“S-shaped” curve - at low doses, the response is small, at higher doses, the response is maximal and plateaus

43
Q

What does the plateau indicate on the log-rhythmic scale?

A

That a further increase in the drug won’t increase the response

44
Q

What does potency mean?

A

Amount of drug required in order to get maximal effect

- More potent, smaller therapeutic index

45
Q

What is efficacy?

A

Sum of max effect

46
Q

What is variability?

A

Described by frequency distribution - lots of individual variation of where curve actually lands

47
Q

What is relative potency?

A

The ratio of 2 drugs to produce the same intensity of effect

48
Q

What is the drug response curve?

A

Describes a relationship between a change in the dose given and a change in the effect

49
Q

What does maximal efficacy depend on?

A

The intrinsic activity of the drug.

50
Q

What is the median effective dose (ED50)?

A

The dose of a drug required to produce an effect in 50% of people who receive it.

51
Q

What is the median lethal dose?

A

A dose of a drug that is lethal to 50% of the exposed subjects

52
Q

What is the therapeutic index?

A

Relationship between the lethal dose 50 to the effective dose 50. This also tells us how gently we need to handle the drug.

Narrower the therapeutic index, more potent the drug is.

53
Q

What is the equation for safety margin?

A

LD1-ED99/ED99x100

54
Q

Is safety margin used often? Why or why not?

A

No, need very large number of subjects to obtain reliable estimates of 1st and 99th percentiles

55
Q

What is the equation for therapeutic index?

A

LD50/ED50

56
Q

What is the ED50 also known as?

A

MAC

57
Q

What is MAC?

A

ED50 - minimal alveolar concentration - concentration of anesthetic in the alveoli of the lungs at which 1/2 of patients won
t move on surgical stimulation.

58
Q

If ED50 goes up while the LD 50 remains unchanged what are we at greater risk for?

A

Toxicity because the therapeutic index goes down.

59
Q

What type of affinity for the receptor does a competitive agonist have?

A

Weak

60
Q

What type of affinity does a no competitive agonist have?

A

Strong via covalent bonds

61
Q

what are the goals of anesthesia?

A
  • analgesia
  • amnesia
  • muscle relaxation
  • safe and uneventful emergence from the anesthetic

Anesthesia Pharm (5 decks)

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