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MLSCI 466 > Pharmacokinetics and Pharmacodynamics > Flashcards

Pharmacokinetics and Pharmacodynamics Flashcards

1
Q

What is pharmacokinetics

A

uses math to describe the fate of a drug with dosing schedule and route of administration

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2
Q

what is pharmacodynamics

A

the interaction of a drug on the body receptors

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3
Q

What is LADME

A

Liberation
Absorption
Distribution
Metaboilsm
Elimination

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4
Q

What is the concept of LADME

A

determine how rapid, in what concentration and how long the drug takes to reach the target organ

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5
Q

T/F - availability is a function of liberation and absorption

A

T

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6
Q

What factors affect absorption of drugs in the GI

A

food
pH
surface area
enzyme and microflora

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7
Q

what factors influences absorption

A

GI factors
physiochemical drug properties
transporters
route of administration

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8
Q

how do large charged molecules cross the lipid bilayer

A

active transport

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9
Q

How does the Henderson Hassel Balch predict the absorption capacity of a drug

A

calculate the pH to determine if pH of environemnt < pKa of drug. charged molecules = less absorbed

If pH< weak acid pKa = not ionized
If pH < weak base pKa = ionized

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10
Q

Is aspirin (pKa = 3.5) absorbed in the stomach or intestines more?

A

stomach - acidic nature turns aspirin neutral as pH < pKa = easier to absorb

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11
Q

What is the best indicator of total exposure to a dose of drug

A

Area Under the curve

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12
Q

What is bioavailability

A

amount of drug that reaches the circulation

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13
Q

How to calculate bioavailability?

A

ratio of AUC (alternative) / AUC (intravenous)

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14
Q

what is first pass metabolism

A

liver and intestine reduce administered drug bioavailability

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15
Q

What does a F =1 mean

A

complete absorption (intravenous)

F <1 = extra vascular

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16
Q

What is F and S in the effective dose calculation

A

S = chemical form = active form of drug salts
F = bioavailability factor = dose that reaches circulation

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17
Q

T/F - bioavailability estimates extent and rate of absorption

A

F - bioavailibity only estimates extent and NOT rate of absorption

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18
Q

what does a large volume of distribution mean (Vd)

A

concentration in tissues > concentration in plasma

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19
Q

what is the relationship of Vd and water solubility and plasma concentration

A

increase water solubility = increase plasma conc = DECREASE Vd

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20
Q

What is the relationship of plasma protein binding (PPB) and plasma concentration and Vd

A

low PPB = low plasma conc = INCREASE Vd

eg. liver cirrhosis = less albumin is made = high Vd for an albumin bound drug in the tissue than plasma

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21
Q

why is Vd important?

A
  1. determines if dialysis of a drug is benefitial
  2. estimates body burden of drug (amount)
  3. Calculates loading dose
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22
Q

how to calculate amount of drug

A

amount = Vd x weight x Cp (concentration of plasma)

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23
Q

what are the units of Vd

A

ug/L

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24
Q

ug to mg conversion

A

ug / 1000 = mg

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25
what factors effect Vd (2)
1. drug solubility 2. plasma protein binding
26
clearance definition
volume of plasma (NOT VOLUME OF DRUG) cleared of drug per unit time through metabolism and excretion
27
what are the components in the clearance equation Cl= Vd x Kel
Vd = volume of distribtion Kel = elimination constant
28
how to figure out Kel from graph
log of AUC elimination phase slope gives - Kel
29
how does half life relate to time to steady state
steady state is assumed to be reached in 5 half lives time to acheive steady state influenced by half life
30
what is steady state concentration determined by
dose and frequency of dose
31
what must the time units be in steady state
mg/ minute
32
what is first order elimination
rate of drug clearance is proportional to drug concentration. the drug PERCENTAGE is removed at constant rate
33
what is zero order elimination
drug clearance is CONSTANT regardless of drug concentration
34
when is zero order elimination seen
when drugs saturate elimination mechanism (enzymes/transporters) eg. alcohol and aspirin
35
what is used to sop up drugs that undergo enterohepatic circulation
activated charcoal
36
what is enterohepatic recirculation
when the drug gets reabsorbed in the small intestine to the liver over and over again
37
what are the two phases of hepatic elimination of drugs
phase 1 chemical reaction phase 2 conjugate reaction
38
process of renal elimination of drugs
1. glomerular filtration - passive 2. proximal tubular secretion - active 3. distil tubular reabsorption - passive
39
what factors affect renal excretion
PPB urine pH kidney function
40
If a patient overdosed on amphetamines (basic), would you acidify or alkalinize the urine to clear the drug?
acidify - it ionizes the drug to promote elimination (if it was alkalinized, the nonionized drug will get reabsorbed)
41
what factors affects pharmacokineteic properties
1. AGE 2. gender 3. pregnancy 4. disease
42
what are xenobiotics
organic compounds foreign to the body eg drugs, pesticides, pollutant, toxins
43
what is the goal of xenobiotic metabolism
harmful molecules can be lipophilic = reabsorbed in the body. We want to excrete these molecules
44
How can xenobiotics be metabolized
biotransformation = enzymatic transformation by functionalization (phase 1) and conjugation (phase 2) into water soluble
45
functionalization (phase 1) process
1. introduction 2. exposure or modification (eg oxidation reduction) 3. (optional) conjugation in phase 2
46
T/F - increase polarity / hydrophilicity dissolves xenobiotics in urine for elimination
T
47
Process of acetaminophen metabolism
CYP2R1 converts APAP into NAPQI NAPQI destroys liver cells unless bound to glutathione glutathione removed = damage to liver
48
Where can biotransformation occur
Major = liver but all tissues can metabolize
49
what enzymes are used for biotransformation
cytosolic enzyme or membrane anchored enzymes in ER
50
what are CYP enzymes structural components and function
1. hemoprotein - oxygen binding due to protoporphyrin IX containing heme 2. flavoprotein - cofactor NADPH 3. heat stable lipid component - holds everything together
51
where did the name CYPP450 come from
P = red liver pigment 450 = max light absorption
52
what is CYP450 used for
detoxify, generate energy, create hormones, abosorption/digestion
53
How can host factors modify metabolism
can inhibit or induce CYP metabolism based on diet and disease
54
How do brassica (brocoli) affect CYP1A2
increase activity
55
how do apiaceous (celery /carrots) affect CYP1A2
decrease activiity
56
how does grapefruit juice affect CYP3A4
stops actvitiy
57
how does aging affect CYP
slight decrease activity
58
Define pharmacogentics
study of genetically determined variation in drug metabolism
59
What are extensive metabolizers (EM)
person who metabolizes a drug at similar rate as to the population
60
what are poor metabolizers (PM) and what is the consequence?
person who responses drug at a slower rate than population lack response = inability to convert drug into active form = toxic side effects of prodrug accumulation
61
what are ultra rapid metabolizers (URM) and what are the consequences
person who metabolizes drugs rapidly due to multiple copies of CYP2D6 gene fail to respond to normal doses of drug = need very high doses for effects
62
How does the CYP2D6 impact codeine metabolism
Fluoxetine is a codeine drug that uses CYP2D6 to turn into morphine
63
URM mother breastfeeding complications without CYP2D6 mutation
Taking codeine at higher dose for effect. CYP2D6 converts all into morphine (hydrophobic/nonpolar) and leaks into breastmilk. Baby drinks all the morphine
64
Does CYP2C9 metabolize S or R warfarin
CYP2C9 metabolizes S-warfarin (5x stronger than R-warfarin)
65
What are the allelic variants of warfarin metabolism and what do they mean
CYP2C9*1 = wildtype CYP2C9*2 and CYP2C9*3 = slow metabolism
66
how does warfarin get metabolized
S warfarin utilizes CYP2C9 to metabolize or inihibtion on K for activation of clotting factors for efficient warfarin clotting
67
how to resolve excess warfarin?
give more vit K
68
T/F Clopidogrel is a prodrug
T - Clopidogrel is a prodrug as it has to be metabolised into its active form
69
What gene impacts codeine metabolism
CYP2D6
70
what gene impacts warfarin metabolism
CYP2C9
71
what gene impacts clopidogrel metabolism
CYP2C19
72
How does the CYP2C19 gene impact clopidogrel metabolism
No gene = wt detection of gene = altered enzymatic activity and slow clopidogrel metabolism
73
how does enzyme induction work
increase CYP enzyme expression by increasing synthesis and decreasing degradation
74
what process is seen in ethanol abuse in acetaminophen metabolism
enzyme induction
75
What happens when ethanol abuse occurs with acvetaminophen
- ethanol induces CYP2E1 enzyme which increases acetaminophen metabolism of NAPQI (toxic) - ethanol depletes glutathione stores
76
3 Types of inhibition from drugs or xenobiotics
1. substrate (reversible) 2. non substrate (reversible) 3. metabolite inhibition (irreversible / suicide)
77
What happens when terfenadine is administered with an inhibitor
cardiac arrest
78
3 types of immunosuppressants
cyclosporin tacrolimus sirolimus
79
how does cyclosporin work
- based from fungi amino acids (tolypocladium inflatum) - used as first line immunosuppressant - inhibiting calcineurin to block NFAT-mediated transcription of IL-2
80
how does sirolimus work (rapamycin)
- binds FKBP12 to inhibit mTOR = block signaling of IL-2 - used with cyclosporin
81
how does Tacrolimus work (FK506)
- isolated from bacterium (streptomyces tsukubaensis) - 100x more potent than cyclosporin - inhibits calcinerurin - current first line immunosuppressant drug in US
82
Which families of CYPP450 are the most important for metabolism
11, 17, 21

MLSCI 466 (8 decks)

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