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pharmacodynamics anesthesia > Test 1 > Flashcards

Test 1 Flashcards

1
Q

The study of intrinsic sensitivity or responsiveness of the body to a drug and the mechanisms by which it occurs. What drug does to body. Effect site concentration and clinical effect

A

Pharmacodynamics

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2
Q

Study of absorption, distribution, metabolism (biotransformation), and excretion of a drug. What body does to a drug.

A

Pharmacokinetics

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3
Q

A protein or other substance that bind to an endogenous chemical or drug

A

Receptor

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4
Q

Properties of receptors

A

Sensitivity
Selectivity
Specificity

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5
Q

Receptor Sensitivity

A

Responsiveness or reactivity of a receptor to a particular ligand or substance

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6
Q

Receptor Selectivity

A

Preference of a ligand for a specific type of subtype of receptor

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7
Q

Receptor Specificity

A

The degree to which a receptor recognizes and binds to a particular ligand over other substances

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8
Q

Drug receptor classification

A

Generic characterization, similarity of structure and function

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9
Q

Examples of receptor classifications

A

G protein coupled, ligand gated ion channels, ion channels, catalytic receptors, nuclear receptors, transporters, enzymes

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10
Q

Receptor locations

A

Lipid bilayer of cell membrane
Intracellular proteins
Circulating proteins
Also there are drugs that do not interact with proteins at all

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11
Q

One of many mechanisms that contribute to variability in drug response

A

Changing number of receptors aka upregulation or downregulation

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12
Q

Signal transduction

A

Process by which a cell converts one kind of signal or stimulus into another
Ordered sequences or cascades of biochemical reactions inside the cell
ex. second messenger pathways

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13
Q

Drug response equation

A

Drug + Receptor⇆ (Drug Receptor Complex)⇄ Tissue Response
Fundamental to pharmalogic principles and derived from the law of mass action

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14
Q

Affinity and Efficacy

A

Describe the degree of drug receptor interaction for a given drug and receptor protein population

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15
Q

Affinity

A

Potency. Strength of binding to receptors. Weak affinity can be bumped off by something with strong affinity. Ex Aspirin has STRONG affinity

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16
Q

Efficacy

A

The ability of a drug to produce the desired effect or maximum response. The magnitude of a response with respect to a given dose. (dilaudid vs. morphine)

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17
Q

Pure antagonists

A

Have receptor affinity BUT lack intrinsic efficacy or activity. Similar in structure to corresponding agonist.

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18
Q

Competitive antagonists

A

Have a weak affinity for the same receptor protein and may be displaced by an agonist
Ex. Atropine and esmolol

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19
Q

Noncompetitive antagonists

A

Have a strong affinity for the receptor protein and cannot be displaced by the agonist
Ex. Aspirin

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20
Q

Agonist Antagonist

A

Second major type of antagonist drugs. Have receptor protein affinity and intrinsic activity, but often only a fraction of the potency of the full agonist.
Ex. Nalbuphine

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21
Q

Physiological antagonism

A

two AGONIST drugs that bind to different receptors. Both drugs bind to specific unrelated receptor proteins, initiate a protein conformational shift, illicit individual tissue responses. Responses generate opposing forces.
Ex. Isopreteronol vasodilation and NE induced vasoconstriction. Net effect is less than if either drug were used alone.

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22
Q

Chemical antagonism

A

When a drug’s action is blocked and no receptor activity is involved.
Ex. protamine forms an ionic bond with heparin and renders it inactive

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23
Q

Full agonist

A

Binds to a receptor site and turns on response, mimics endogenous ligand, produces maximal effect.
Ex. Dopamine, propofol

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24
Q

Down regulation is continued stimulation of cells with

A

AGONISTS. Results in states of desensitization. The effects of same amounts of drug are diminished (because now there’s not as many receptors) and more drug is required.

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25
Q

Up-regulation happens with chronic administration of

A

ANTAGONISTS. The number and sensitivity of the receptors increases as response to chronic blockade. Pt develops tolerance and requires higher doses of antagonists.

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26
Q

Drug interaction

A

Alteration in the therapeutic action of a drug by concurrent administration of another drug or substance

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27
Q

Types of drug interaction

A

Addition
Synergism
Potentiation
Antagonism

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28
Q

Addition

A

1+1=2

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29
Q

Synergism

A

1+1=3

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30
Q

Potentiation

A

1+0=3

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31
Q

Antagonism

A

1+1=0

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32
Q

The drug interaction between most anesthetics is

A

Syngergism

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33
Q

Properties influencing pharmacokinetics

A

Molecular size
Transporters
Lipid solubility and degree of ionization
Ion trapping
Protein binding

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34
Q

Molecular Size

A

The smaller the agent, the easier it crosses lipid membranes and membranes of tissues

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35
Q

Transporters

A

Control entry and exit molecules. Can affect bioavailability, clearance, volume of distribution, and half life for orally dosed drugs

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36
Q

Drive their substrates out of the cell

A

Efflux transporters.

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37
Q

Transfer their substrates into cells

A

Uptake transporters

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38
Q

Water soluble form of a drug

A

Ionized (charged).
Not absorbed well orally and not metabolized by the liver.
Excreted via the renal system.

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39
Q

Lipid soluble form of drug

A

Nonionized (uncharged)
Able to cross membranes easily.
Cannot be excreted by the kidneys so it gets reabsorbed for metabolism by the liver.

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40
Q

Degree of ionization is determined by

A

the dissociated constant or pKa

pH of surrounding fluid

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41
Q

When pH and pKa are identical

A

50% of drug is ionized and 50% is unionized

42
Q

Acids are proton

A

Donors

43
Q

Bases are proton

A

Acceptors

44
Q

Acidic drugs (barbiturates) are highly ionized at a

A

alkaline pH

45
Q

Acidic drugs are nonionized in a

A

acidic pH

46
Q

Basic drugs (opioids and LA) are highly ionized in a

A

Acidic pH

47
Q

Basic drugs are nonionized in a

A

alkaline pH

48
Q

Ion trapping

A

occurs when an ionized drug (WEAK acids or bases) gets trapped on one side of a membrane that divides compartments of two different pHs. Ex mom gets lidocaine (weak base), crosses placenta easily in unionized form, becomes ionized in acidic fetal environment, gets trapped and cannot cross back over

49
Q

Plasma Proteins

A

Albumin: favors Acidic compounds (but will also bind with basic and neutral)
A1 Acid Glycoprotein: favors basic compounds
B Globulin: Favors basic drugs

50
Q

Protein binding affects

A

Distribution: Free or unbound fraction readily crosses membranes
Potency: The free fraction is able to bind to a receptor site

51
Q

Degree of protein binding is proportional to the drug’s:

A

Lipid solubility

52
Q

Most drugs are cleared via what order kinetics

A

First order kinetics

53
Q

Drugs cleared via zero order kinetics

A

Phenytoin, ETOH, Aspirin, warfarin, heparin

54
Q

What is constant in First order kinetics

A

Fraction of the drug eliminated. Half Life.

55
Q

What is constant in Zero order Kinetics

A

Amount of drug eliminated regardless of plasma concentration

56
Q

When is the greatest amount of drug eliminated per unit time in first order kinetics

A

When the drug concentration is highest

57
Q

First order kinetics graph is

A

CURVED

58
Q

Zero order kinetics graph is

A

LINEAR

59
Q

Population variability

A

Range of responses to a given drug
Affected by age, sex, body weight, bsa, basal metabolic rate, pathologic state, and genetic profile

60
Q

Therapeutic dose

A

ED50. Average dose of a “normal” population of people

61
Q

Therapeutic index

A

The distance between the LD50 and TD50
LD50/TD50

62
Q

Drug Response equation

A

Derived from law of mass action.
The magnitude of a drug’s effect is directly proportional to number of receptors occupied

63
Q

The arithmetic average of the range of doses that produce a given response

A

Mean

64
Q

The middle. Half of responses occur on either side

A

Median

65
Q

The dose representing the greatest percentage of responses. Shows up most frequently.

A

Mode

66
Q

Provides information regarding actual responses measured and their difference from the calculated mean

A

Standard deviation

67
Q

The mean reflects the central tendency of responses LESS when the SD is

A

greater

68
Q

Describes the variance of the mean

A

Standard error of the mean

69
Q

A proportional expression that relates the amount of drug in the body to the serum concentration.

A

Volume of distribution
The apparent volume into which the drug has been distributed after being introduced to the body

70
Q

Vd=

A

dose of drug/plasma concentration

71
Q

Large Vd implies

A

widely distributed, highly lipid soluble, unionized

72
Q

Small Vd implies

A

largely contained in plasma, water soluble, ionized

73
Q

Steady State

A

Drug elimination = drug administration
Stable plasma concentration is achieved and all body compartments equilibrate

74
Q

Elimination of the drug by the GI system before the drug reaches systemic circulation

A

Presystemic elimination

75
Q

Mechanisms of presystemic elimination

A
  1. Stomach acids hydrolyze the drug
  2. Enzymes in the GI wall deactivate the drug
  3. Liver biotransforms the ingested drug before it reaches the effect site (First pass effect)
76
Q

Best med route for prevention of emesis caused by irritation of GI mucosa

A

Rectal
Proximal rectal undergoes first pass
Distal rectal does not

77
Q

Systemic absorption of IM and SQ routes is dependent on:

A

Capillary blood flow to the area and lipid solubility of the agent

78
Q

Transdermal route drugs must have what solubility

A

Water soluble: penetrate hair follicles and sweat ducts
AND
Lipid soluble: traverse skin and exert effect at the receptors

79
Q

Converts pharmacologically active, lipid-soluble drugs into water-soluble inactive metabolites

A

Metabolism

80
Q

Main organ of metabolism

A

Liver

81
Q

Phase 1 Metabolism

A

Modification

82
Q

Phase 2 Metabolism

A

Conjugation

83
Q

Phase 3 Metabolism

A

Elimination

84
Q

Phase 1 Reactions

A

Increase the polarity of the molecule, transforming a lipid-soluble compound to a water-soluble one:
Oxidation
Reduction
Hydrolysis

85
Q

Oxidation

A

Phase 1: adds an O2 molecule to a compound. Catalyzed by enzymes of the P450 system

86
Q

Reduction

A

Phase 1: Adds electrons to a compound. Using P450 system

87
Q

Hydrolysis

A

Phase 1: adds H2O to a compound to split it apart

88
Q

Conjugation

A

Phase 2: Adds on an endogenous, highly polar, water-soluble substrate.
Results in a biologically inactive molecule to prepare for elimination.

89
Q

Common substrates for conjugation

A

Glucuronic acid, sulfuric acid, glycine, acetic acid, or a methyl group

90
Q

Increased enzyme activity by stimulating enzymes over a period of time

A

Enzyme induction

91
Q

Increased capacity to clear drug =

A

Reduction in half-lives. Important for dosing intervals

92
Q

Common enzymes inducers

A

Tobacco, barbiturates, ethanol, phenytoin, rifampin, carbamazepine

Increased clearance, decreased drug plasma levels, dose increase may be required

93
Q

Common enzyme inhibitors

A

Grapefruit juice, cimetidine, omeprazole, SSRIs, erythromycin, ketoconazole, isoniazid

Decreased clearance, increased plasma drug levels, dose decrease may be required

94
Q

Elimination

A

Phase 3: Half-life - time necessary for the plasma content of a drug to drop to half of its prevailing concentration after rapid bolus injection.

95
Q

When is drug regarded as being fully eliminated

A

When 95% has been eliminated OR 4-5 half lives

96
Q

An independent value governed by the properties of the drug and the body’s capacity to eliminate it

A

Clearance

97
Q

Clearance is directly proportional to

A

The dose

98
Q

Clearance is inversely related to

A

the Half-Life and the concentration in the central compartment

99
Q

Drugs with a high extraction ratio 0.7 or greater

A

Perfusion-dependent elimination. Rely heavily on the perfusion of the liver to be cleared

100
Q

Drugs with low extraction ratio 0.3 or less

A

Capacity-dependent elimination.
Clearance depends on hepatic enzymes and the degree of protein binding

101
Q

Other factors effecting metabolism

A

Age, Gender, Temperature (hypothermia impairs metabolism), disease states

pharmacodynamics anesthesia (4 decks)

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