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N926 Pharmacology > PK > Flashcards

PK Flashcards

1
Q

Pharmacokinetics

A 
What the body does to the drug
Absorption
Distribution
Metabolism
Excretion
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2
Q

Factors Influencing PK

A 
Ionization & lipid solubility
Ion trapping
Protein binding
Molecular size
Drug transporters
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3
Q

Dissociation Constant

A

pKa
pH when drug 50% ionized & 50% non-ionized
Measures ionization extent

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4
Q

Acid

A

Proton donors

Weak acid non-ionized when protonated HA

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5
Q

Base

A

Proton acceptors

Weak base ionized when protonated BH+

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6
Q

Non-Ionized

A 
Neutral
Active form
Lipid soluble
Readily crosses membranes (blood-brain barrier, placenta, GI tract)
Undergoes tubular reabsorption
Hepatic metabolism
No renal excretion
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7
Q

Ionization

A 
Charged +/-
Inactive
No pharmacological effects
Water soluble
Renal excretion
Unable to cross membranes
No tubular reabsorption or hepatic metabolism
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8
Q

Ion Trapping

A

Maternal-fetal drug transfer

Local anesthetic toxicity

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9
Q

Protein Binding

A

Liver or kidney disease, poor nutrition, 3rd trimester ↓ protein availability
Albumin - most prominent protein; preferentially bonds w/ acids
Alpha 1 acid protein preferentially bonds w/ bases
Extensive binding slow drug elimination

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10
Q

Absorption

A 
Bioavailability
Amount drug able to produce effect after entering the body
- Drug & patient factors
- First-pass effect (prodrugs)
Plasma distribution curve
- Alpha 1st phase (distribution)
- Beta 2nd phase (elimination)
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11
Q

First-Pass Effect

A

Enteral administration
GI tract to portal circulation
Decreases bioavailability

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12
Q

Distribution

A

Two-compartment model
Central: Vasculature & vessel-rich tissues 10% body mass 75% CO
Peripheral: Muscle fat & bone 90% body mass 25% CO

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13
Q

Vd

A

Volume of distribution
Drug distribution & redistribution before elimination
Affected by drug properties
Amount drug in body / serum concentration
Normal Vd = 0.6L/kg
Large > 0.6L/kg
Small < 0.4L/kg

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14
Q

Body Fluid Compartments

A 
TOTAL:  42L
Intracellular 28L
Extracellular 14L 
- ISF 10L
- Plasma 4L
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15
Q

Metabolism

A

Biotransformation
Enzyme-catalyzed change in chemical structure
Liver 1° metabolism organ
Goal: Convert lipid soluble agents into water soluble forms

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16
Q

First-Order

A

Drug cleared at rate proportional to amount present in plasma
50%

17
Q

Zero-Order

A

Drug cleared at constant rate regardless plasma concentration
Alcohol

18
Q

Phase I

A 
Increases polarity
Lipid to water-soluble
Oxidation 
Reduction
Hydrolysis
19
Q

Oxidation

A

Oxygen introduced into the molecule
Catalyzed by CYP-450 enzymes
Results in electron loss
↑ polarity

20
Q

Reduction

A

CYP-450 transfer enzymes directly to the substrate
Occurs when insufficient oxygen available to compete for electrons
Results in electron gain
↑ polarity

21
Q

Hydrolysis

A

Add H2O to ester or amide to break the bond into 2 smaller molecules

22
Q

Phase II

A

Conjugation
Synthetic reactions - forms new compound
Drug or metabolite conjugated w/ endogenous substance (glucuronic, sulfonic, or acetic acid)

23
Q

CYP-450 Enzymes

A

Cytochrome (CY) P-450 microsomal enzymes found in smooth ER
Iron-containing hemoprotein
Peak absorption 450nm when reacting w/ carbon monoxide
Mixed function oxidase system

24
Q

Enzyme Induction

A

↑ activity by stimulating enzymes over time period
Chronic alcohol abuse induces enzymatic activity
Enzymes quickly break agents down → reduction in half-life

25
Q

Enzyme Inhibition

A

Exposure to certain drugs leading to agent accumulation
↑ plasma levels
Potential for increased drug activity or toxicity

26
Q

Elimination

A

Drug removal from body
Metabolism + excretion
Impacting factors: Drug properties, organ function, concomitant medications, genetic variations

27
Q

Clearance

A

Volume plasma drug completed cleared via metabolism & excretion
Impacted by drug properties & body ability to clear
Directly proportional to dose
Inversely r/t half-life
Clearance organs - liver & kidney
Determined by blood flow & organ ability to extract drug from blood

28
Q

Hepatic Clearance

A

Perfusion dependent elimination > 0.7L/kg
High extraction ratio
↓ perfusion ↓ clearance

Capacity dependent elimination - small drug amount removed per unit time
Low extraction ratio < 0.3L/kg
Hepatic perfusion does not have significant effect on clearance
Dependent on hepatic enzymes & protein binding
↓ protein binding ↑ clearance

29
Q

Elimination Half-Life

A

Time necessary for plasma concentration drug to decrease by half
1° first-order kinetics (drug removed at constant rate)
Drug eliminated after 4-5 half-lives
Frequent dosing = accumulation

30
Q

Context Sensitive Half-Time

A

Continuous infusion
Time required for infusion maintained at constant concentration to decrease by 50%
Increases (accumulates) w/ longer infusions

31
Q

Renal Clearance

A

Kidney efficient at removing water-soluble molecules
Actively secreted substances include: Morphine, meperidine, furosemide, penicillin, quaternary ammonium
Urine pH influences drug elimination
Weak acids better excreted in alkaline urine
Weak bases better excreted in acidic urine

32
Q

Excretion

A

Passive glomerular filtration
Water-soluble metabolites filtered & eliminated
Active tubular secretion
Lipid soluble molecules reabsorbed & placed back into circulation

33
Q

Elderly PK

A 
Slow drug absorption
↑ adipose tissue percentage
↑ Vd
↓ plasma proteins
↓ hepatic blood flow & metabolism
↓ CO
Prolonged circulation = slower onset ჻ remains in CNS longer
↓ renal function
34
Q

Chronic Kidney Disease

A

↓ clearance & elimination
Protein binding impairment
Metabolizing enzymes & J-drug transporters

35
Q

Chronic Liver Disease

A

Cirrhosis - all processes altered
High portosystemic pressure impedes GI absorption
Protein bound drugs Vd changes to hypoalbuminemia
Ascites impacts Vd
Phase I reactions affected

36
Q

Pharmacogenetics

A

Variation in human genes responsible for different responses to drug therapy
Involves identifying drug response markers at disease level, metabolism, or target
Polymorphisms - variations in DNA sequences that occur in at least 1% population

N926 Pharmacology (17 decks)

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