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pharmacodynamics anesthesia > Test 1 > Flashcards

Test 1 Flashcards

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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
Up-regulation happens with chronic administration of
ANTAGONISTS. The number and sensitivity of the receptors increases as response to chronic blockade. Pt develops tolerance and requires higher doses of antagonists.
26
Drug interaction
Alteration in the therapeutic action of a drug by concurrent administration of another drug or substance
27
Types of drug interaction
Addition Synergism Potentiation Antagonism
28
Addition
1+1=2
29
Synergism
1+1=3
30
Potentiation
1+0=3
31
Antagonism
1+1=0
32
The drug interaction between most anesthetics is
Syngergism
33
Properties influencing pharmacokinetics
Molecular size Transporters Lipid solubility and degree of ionization Ion trapping Protein binding
34
Molecular Size
The smaller the agent, the easier it crosses lipid membranes and membranes of tissues
35
Transporters
Control entry and exit molecules. Can affect bioavailability, clearance, volume of distribution, and half life for orally dosed drugs
36
Drive their substrates out of the cell
Efflux transporters.
37
Transfer their substrates into cells
Uptake transporters
38
Water soluble form of a drug
Ionized (charged). Not absorbed well orally and not metabolized by the liver. Excreted via the renal system.
39
Lipid soluble form of drug
Nonionized (uncharged) Able to cross membranes easily. Cannot be excreted by the kidneys so it gets reabsorbed for metabolism by the liver.
40
Degree of ionization is determined by
the dissociated constant or pKa pH of surrounding fluid
41
When pH and pKa are identical
50% of drug is ionized and 50% is unionized
42
Acids are proton
Donors
43
Bases are proton
Acceptors
44
Acidic drugs (barbiturates) are highly ionized at a
alkaline pH
45
Acidic drugs are nonionized in a
acidic pH
46
Basic drugs (opioids and LA) are highly ionized in a
Acidic pH
47
Basic drugs are nonionized in a
alkaline pH
48
Ion trapping
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
Plasma Proteins
Albumin: favors Acidic compounds (but will also bind with basic and neutral) A1 Acid Glycoprotein: favors basic compounds B Globulin: Favors basic drugs
50
Protein binding affects
Distribution: Free or unbound fraction readily crosses membranes Potency: The free fraction is able to bind to a receptor site
51
Degree of protein binding is proportional to the drug's:
Lipid solubility
52
Most drugs are cleared via what order kinetics
First order kinetics
53
Drugs cleared via zero order kinetics
Phenytoin, ETOH, Aspirin, warfarin, heparin
54
What is constant in First order kinetics
Fraction of the drug eliminated. Half Life.
55
What is constant in Zero order Kinetics
Amount of drug eliminated regardless of plasma concentration
56
When is the greatest amount of drug eliminated per unit time in first order kinetics
When the drug concentration is highest
57
First order kinetics graph is
CURVED
58
Zero order kinetics graph is
LINEAR
59
Population variability
Range of responses to a given drug Affected by age, sex, body weight, bsa, basal metabolic rate, pathologic state, and genetic profile
60
Therapeutic dose
ED50. Average dose of a "normal" population of people
61
Therapeutic index
The distance between the LD50 and TD50 LD50/TD50
62
Drug Response equation
Derived from law of mass action. The magnitude of a drug's effect is directly proportional to number of receptors occupied
63
The arithmetic average of the range of doses that produce a given response
Mean
64
The middle. Half of responses occur on either side
Median
65
The dose representing the greatest percentage of responses. Shows up most frequently.
Mode
66
Provides information regarding actual responses measured and their difference from the calculated mean
Standard deviation
67
The mean reflects the central tendency of responses LESS when the SD is
greater
68
Describes the variance of the mean
Standard error of the mean
69
A proportional expression that relates the amount of drug in the body to the serum concentration.
Volume of distribution The apparent volume into which the drug has been distributed after being introduced to the body
70
Vd=
dose of drug/plasma concentration
71
Large Vd implies
widely distributed, highly lipid soluble, unionized
72
Small Vd implies
largely contained in plasma, water soluble, ionized
73
Steady State
Drug elimination = drug administration Stable plasma concentration is achieved and all body compartments equilibrate
74
Elimination of the drug by the GI system before the drug reaches systemic circulation
Presystemic elimination
75
Mechanisms of presystemic elimination
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
Best med route for prevention of emesis caused by irritation of GI mucosa
Rectal Proximal rectal undergoes first pass Distal rectal does not
77
Systemic absorption of IM and SQ routes is dependent on:
Capillary blood flow to the area and lipid solubility of the agent
78
Transdermal route drugs must have what solubility
Water soluble: penetrate hair follicles and sweat ducts AND Lipid soluble: traverse skin and exert effect at the receptors
79
Converts pharmacologically active, lipid-soluble drugs into water-soluble inactive metabolites
Metabolism
80
Main organ of metabolism
Liver
81
Phase 1 Metabolism
Modification
82
Phase 2 Metabolism
Conjugation
83
Phase 3 Metabolism
Elimination
84
Phase 1 Reactions
Increase the polarity of the molecule, transforming a lipid-soluble compound to a water-soluble one: Oxidation Reduction Hydrolysis
85
Oxidation
Phase 1: adds an O2 molecule to a compound. Catalyzed by enzymes of the P450 system
86
Reduction
Phase 1: Adds electrons to a compound. Using P450 system
87
Hydrolysis
Phase 1: adds H2O to a compound to split it apart
88
Conjugation
Phase 2: Adds on an endogenous, highly polar, water-soluble substrate. Results in a biologically inactive molecule to prepare for elimination.
89
Common substrates for conjugation
Glucuronic acid, sulfuric acid, glycine, acetic acid, or a methyl group
90
Increased enzyme activity by stimulating enzymes over a period of time
Enzyme induction
91
Increased capacity to clear drug =
Reduction in half-lives. Important for dosing intervals
92
Common enzymes inducers
Tobacco, barbiturates, ethanol, phenytoin, rifampin, carbamazepine Increased clearance, decreased drug plasma levels, dose increase may be required
93
Common enzyme inhibitors
Grapefruit juice, cimetidine, omeprazole, SSRIs, erythromycin, ketoconazole, isoniazid Decreased clearance, increased plasma drug levels, dose decrease may be required
94
Elimination
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
When is drug regarded as being fully eliminated
When 95% has been eliminated OR 4-5 half lives
96
An independent value governed by the properties of the drug and the body's capacity to eliminate it
Clearance
97
Clearance is directly proportional to
The dose
98
Clearance is inversely related to
the Half-Life and the concentration in the central compartment
99
Drugs with a high extraction ratio 0.7 or greater
Perfusion-dependent elimination. Rely heavily on the perfusion of the liver to be cleared
100
Drugs with low extraction ratio 0.3 or less
Capacity-dependent elimination. Clearance depends on hepatic enzymes and the degree of protein binding
101
Other factors effecting metabolism
Age, Gender, Temperature (hypothermia impairs metabolism), disease states

pharmacodynamics anesthesia (4 decks)

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