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Fundamentals Block 1 > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

What four factors are involved in the study of pharmacokinetics?

A

absorption, distribution, metabolism, and excretion

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2
Q

After providing a dose, what 4 things can determine concentration in the blood?

A
  1. absorption (gi, pH, rate)
  2. distribution (theoretical)
  3. elimination (metabolism, excretion, dialysis)
  4. dosing interval
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3
Q

What determines how drug concentration in the blood gets to concentration at the site of action?

A

Distribution

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4
Q

What is first order kinetics for drug elimination (excretion/metabolism/dialysis)?

A

It means that a constant FRACTION of drug is removed per unit time NOT a constant AMOUNT of drug.

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5
Q

As the concentration of drugs in the plasma decreases, what happens to the Ke in first order kinetics?

A

The elimination rate slows as the concentration of drug decreases because a fraction is removed per unit time

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6
Q

What is meant by zero-order kinetics?

A

A constant amount (NOT fraction) of drugs is eliminated per unit time because it is saturable.

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7
Q

What are the three common drugs that follow zero-order kinetics?

A
  1. phenytoin
  2. ethanol
  3. salicylates
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8
Q

If a drug has a high Km, what does that say about the affinity?

A

low affinity

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9
Q

Most enzymes of drug metabolism and physical excretion mechanisms have _____________values of Km and _________ capacity overall.

A

high values of Km (low affinity)

high capacity overall (can clear a wide variety of toxins

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10
Q

What kind of dose (oral, topical, IV) will have first order elimination kinetics?

A

oral and IV

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11
Q

What is the therapeutic index?

A

The logarithmic concentration of drugs between toxicity and therapeutic benefit

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12
Q

For first order kinetics, as the drug concentration increases, the elimination rate (Ke) __________________.

A

increases

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13
Q

In a graph of serum concentration (log) over time, the straight terminal segment is called the _____________. What is the slope of this part of the graph?

A

serum decay curve

Slope= -Ke/2.3

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14
Q

What are the units of Ke?

A

inverse of time (1/time)

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15
Q

In regards to the elimination constant, what does t1/2 equal?

A

T1/2= 0.693/ke

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16
Q

The initial drug concentration at t=0 can be used to calculate ________________ if you are given the __________/

A

volume of distribution if you are given the bioavailability

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17
Q

If a graph of serum concentration over time doesn’t show an initial rise in serum concentration, what can be said about how the dose was administered?

A

It means that there was no absorption phase so the dose must have been given via IV

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18
Q

With IV administration, what are the two phases of decay?

Which is slower?

A
  1. distribution phase- where it leaves serum to enter tissue (stores, target tissue, etc)
  2. elimination phase (*slower phase)
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19
Q

If you extrapolate the serum decay line to the Y-itercept, what value would it tell you?

A

Concentration at time zero which is equal to Dose/Vd

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20
Q

What is an example of a time when Vd would be larger than total body volume?

A

When the drug can distribute into non-plasma compartments like fat

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21
Q

For zero order kinetics, elimination is best characterized by ____ and ____ rather than ____ and ____.

A

Km and Vmax rather than Vd and CL

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22
Q

If you increase the dose for a substance following zero order kinetics, what happens to fractional clearance and half life?

A

The fractional clearance decreases and the apparent half life increases

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23
Q

What happens to the steady state concentration if you increase the dose?

A

It will increase because the elimination rate will increase as well

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24
Q

What is bioavailability?

A

the fractional amount of a dose that gets into the blood (bound or unbound)

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25
Q

What is the bioavailability of a drug administered via IV?

A

F=1

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26
Q

If a drug is administered orally, what two factors determine the bioavailability?

A
  1. amount absorbed

2. amount metabolized by first pass in liver

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27
Q

What does Vd help you determine?

A

Loading Dose

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28
Q

If you want to achieve a certain serum concentration, what equation is used for loading dose?

A

conc = (dosexF)/Vd

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29
Q

What is the purpose of administering a loading dose?

A

to achieve a serum concentration quickly and a therapeutic concentration rapidly

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30
Q

If you do not issue a loading dose, how long would it take to achieve the appropriate steady state concentration?

A

4-5 times the elimination half life

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31
Q

What time frame should loading doses be administered over?

A

3-5 minutes

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32
Q

What is clearance?

What are the units?

A

the amount of blood (or fluid) from which ALL drug is removed per unit time
ml/min

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33
Q

What are the three main types of clearance?

A

blood, plasma, serum

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34
Q

What factor is important for loading dose? What factor is most important for maintenance dose?

A

Loading- Vd

Maintenance- CL

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35
Q

What is the equation for maintenance of steady state concentration?

A

Conc= (Fxdose)/(intervalxCL)

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36
Q

What three factors can influence maintenance of the steady state concentration of a drug?

A
  1. Bioavailability
  2. Dose/dose interval
  3. CL
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37
Q

The more frequent a dosing interval the _________ fluctuation in steady state concentration.

A

less

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38
Q

What is half-life? How is it calculated?

A

t1/2= (0.693Vd)/CL

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39
Q

What happens to the number of half lifes to reach steady state when how often the drug is given is changed?
Dose?
Elimination pattern?

A

The half life stays the same in all situations at about 4-5 half lives to reach steady state

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40
Q

What can be altered to optimize drug absorption at the appropriate site?

A
  1. Drug design
  2. Formulation
  3. delivery of drugs
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41
Q

What five things are absorption dependent on?

A
  1. blood flow
  2. chemical nature of the drug
  3. formulation
  4. disease-induced changes in perfusion
  5. injury to absorption site
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42
Q

Ambient changes to pH that favor _____ species will promote absorption

A

unionized

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43
Q

Weak acids will be more permeant at ____ pH so they are absorbed better in the _________.

A

low; stomach

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44
Q

Weak bases are more permeant at _____ pH so they will be better absorbed in the _____

A

high; intestines

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45
Q

Where will MOST of weak acids be absorbed?

A

despite the fact that they are better absorbed in the stomach, most weak acids will be absorbed in the intestines because they have a longer transit time and surface area

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46
Q

Where will the charged form of a drug be trapped when working with a weak base?

A

It will be trapped on the more acidic side

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47
Q

What is the first pass effect?

A

Drugs that are absorbed in the GI tract go to the liver via portal system before entering circulation. The liver will metabolize a large fraction of the drug

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48
Q

What are the three most important aspects of drug absorption?

A
  1. Lag time (formulation, route, gastric emptying)
  2. Extent of absorption (bioavailability)
  3. Rate of absorption
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49
Q

What five factors determine the bioavailability of a drug?

A
  1. Product formulation
  2. Intestinal transit time
  3. Drug interactions
  4. Food intake
  5. First pass effect
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50
Q

What factors affect the first pass effect?

A
  1. blood flow to the liver

2. capacity of the liver to metabolize the drug

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51
Q

What determines the rate of absorption?

A
  1. Product formulation
  2. Drug interactions
  3. GI physio, path
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52
Q

What five factors affect distribution?

A
  1. Active transport into tissues
  2. Chemical properties (lipid soluble, size, ions)
  3. Binding to plasma proteins
  4. Uptake into sinks (fat, bone, etc)
  5. Tissue perfusion
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53
Q

Where will MOST of weak acids be absorbed?

A

despite the fact that they are better absorbed in the stomach, most weak acids will be absorbed in the intestines because they have a longer transit time and surface area

54
Q

Where will the charged form of a drug be trapped when working with a weak base?

A

It will be trapped on the more acidic side

55
Q

What is the first pass effect?

A

Drugs that are absorbed in the GI tract go to the liver via portal system before entering circulation. The liver will metabolize a large fraction of the drug

56
Q

What are the three most important aspects of drug absorption?

A
  1. Lag time (formulation, route, gastric emptying)
  2. Extent of absorption (bioavailability)
  3. Rate of absorption
57
Q

What five factors determine the bioavailability of a drug?

A
  1. Product formulation
  2. Intestinal transit time
  3. Drug interactions
  4. Food intake
  5. First pass effect
58
Q

What factors affect the first pass effect?

A
  1. blood flow to the liver

2. capacity of the liver to metabolize the drug

59
Q

What five factors affect distribution?

A
  1. Active transport into tissues
  2. Chemical properties (lipid soluble, size, ions)
  3. Binding to plasma proteins
  4. Uptake into sinks (fat, bone, etc)
  5. Tissue perfusion
60
Q

Where does most drug metabolism occur?

A

Liver

61
Q

What accounts for 1/3 of phase one metabolism?

A

Cyp3A4

62
Q

What is the predominant enzyme for phase I drug metabolism?

A

p450s

63
Q

P450s have a ______ substrate range and can catalyze_________ reactions.

A

very broad; many

64
Q

Where will MOST of weak acids be absorbed?

A

despite the fact that they are better absorbed in the stomach, most weak acids will be absorbed in the intestines because they have a longer transit time and surface area

65
Q

Where will the charged form of a drug be trapped when working with a weak base?

A

It will be trapped on the more acidic side

66
Q

What is the first pass effect?

A

Drugs that are absorbed in the GI tract go to the liver via portal system before entering circulation. The liver will metabolize a large fraction of the drug

67
Q

What are the three most important aspects of drug absorption?

A
  1. Lag time (formulation, route, gastric emptying)
  2. Extent of absorption (bioavailability)
  3. Rate of absorption
68
Q

What determines the rate of absorption?

A
  1. Product formulation
  2. Drug interactions
  3. GI physio, path
69
Q

What five factors affect distribution?

A
  1. Active transport into tissues
  2. Chemical properties (lipid soluble, size, ions)
  3. Binding to plasma proteins
  4. Uptake into sinks (fat, bone, etc)
  5. Tissue perfusion
70
Q

What are the three major types of metabolism?

A
  1. Microsomal (ER) cytocrome p450 oxidase
  2. Glucuronide synthesis
  3. Non-microsomal enzymes
71
Q

Where will MOST of weak acids be absorbed?

A

despite the fact that they are better absorbed in the stomach, most weak acids will be absorbed in the intestines because they have a longer transit time and surface area

72
Q

Where will the charged form of a drug be trapped when working with a weak base?

A

It will be trapped on the more acidic side

73
Q

What is the first pass effect?

A

Drugs that are absorbed in the GI tract go to the liver via portal system before entering circulation. The liver will metabolize a large fraction of the drug

74
Q

What are the three most important aspects of drug absorption?

A
  1. Lag time (formulation, route, gastric emptying)
  2. Extent of absorption (bioavailability)
  3. Rate of absorption
75
Q

Most P450 reactions make drugs ___________ which makes them more susceptible for ______________.

A

less hydrophobic making them more susceptible for renal filtration

76
Q

What is autoinduction?

A

When a drug catalyzes its own metabolism

77
Q

What are the most common drug interactions?

A

Inhibition or induction of drug metabolizing enzymes

78
Q

Where does glucuronide metabolism take place?

A

ER- also broad spectrum and inducible like p450

79
Q

What does glucuronide metabolism accomplish?

A

It makes the product more hydrophilic so it can be renally excreted

80
Q

What makes non-microsomal metabolism different from glucuronide and p450 metabolism?

A

It cannot be induced, but it can be competitively inhibited

81
Q

What 5 factors alter drug metabolism?

A
  1. blood flow to the liver
  2. age, sex
  3. disease
  4. drug interactions
  5. genetics
82
Q

Where are most drugs excreted?

What are other options?

A

Kidneys

Lungs, skin, mammary glands

83
Q

What are the four factors to consider for how well a substance will be filtered?

A
  1. glomerular integrity
  2. number of nephrons
  3. size and charge of the molecule
  4. protein binding
84
Q

Molecules under MW ______ can be filtered and under ______ can be filtered well.

A

10,000 filtered, 1000 filtered well

85
Q

The renal tubule can both actively_____ and actively ___ a variety of substates

A

secrete and reabsorb

86
Q

What part of the kidney actively secretes organic acids and bases into the tubular lumen?

A

pars recta (straight part of proximal)

87
Q

The distal nephron is responsible for elimination of what drug? What can compete with this elimination?

A

Digoxin

Competed by: spironolactone, quinidine and verapamil

88
Q

Where does passive reabsorption of weak acids and bases occur?

A

collecting duct

89
Q

What are the two major determinants for passive transport?

A
  1. urine pH

2. flow rate

90
Q

Weak acids are more reasborbed in ______ urine and weak bases are more reabsorbed in _____ urine.

A

acids in acidic pH

bases in basic pH

91
Q

What are two examples of weak acids that would be reabsorbed in acidic urine?

A

barbiturates and salicylates

92
Q

What is an example of a weak base that would be reabsorbed in basic urine?

A

amphetamines

93
Q

Increased renal flow rate ________ excretion.

What are the two factors that make this true?

A

promotes or increases

  1. increased flow = dilute urine= less conc gradient
  2. less time for diffusion
94
Q

Because of varying distribution times, when should you take a patients blood to get accurate levels?

A

just before the next dose

95
Q

Most P450 reactions make drugs ___________ which makes them more susceptible for ______________.

A

less hydrophobic making them more susceptible for renal filtration

96
Q

What is autoinduction?

A

When a drug catalyzes its own metabolism

97
Q

What are the most common drug interactions?

A

Inhibition or induction of drug metabolizing enzymes

98
Q

Where does glucuronide metabolism take place?

A

ER- also broad spectrum and inducible like p450

99
Q

What does glucuronide metabolism accomplish?

A

It makes the product more hydrophilic so it can be renally excreted

100
Q

What makes non-microsomal metabolism different from glucuronide and p450 metabolism?

A

It cannot be induced, but it can be competitively inhibited

101
Q

What 5 factors alter drug metabolism?

A
  1. blood flow to the liver
  2. age, sex
  3. disease
  4. drug interactions
  5. genetics
102
Q

Where are most drugs excreted?

What are other options?

A

Kidneys

Lungs, skin, mammary glands

103
Q

What are the four factors to consider for how well a substance will be filtered?

A
  1. glomerular integrity
  2. number of nephrons
  3. size and charge of the molecule
  4. protein binding
104
Q

Molecules under MW ______ can be filtered and under ______ can be filtered well.

A

10,000 filtered, 1000 filtered well

105
Q

The renal tubule can both actively_____ and actively ___ a variety of substates

A

secrete and reabsorb

106
Q

What part of the kidney actively secretes organic acids and bases into the tubular lumen?

A

pars recta (straight part of proximal)

107
Q

The distal nephron is responsible for elimination of what drug? What can compete with this elimination?

A

Digoxin

Competed by: spironolactone, quinidine and verapamil

108
Q

Where does passive reabsorption of weak acids and bases occur?

A

collecting duct

109
Q

What are the two major determinants for passive transport?

A
  1. urine pH

2. flow rate

110
Q

Weak acids are more reasborbed in ______ urine and weak bases are more reabsorbed in _____ urine.

A

acids in acidic pH

bases in basic pH

111
Q

What are two examples of weak acids that would be reabsorbed in acidic urine?

A

barbiturates and salicylates

112
Q

What is an example of a weak base that would be reabsorbed in basic urine?

A

amphetamines

113
Q

Increased renal flow rate ________ excretion.

What are the two factors that make this true?

A

promotes or increases

  1. increased flow = dilute urine= less conc gradient
  2. less time for diffusion
114
Q

Because of varying distribution times, when should you take a patients blood to get accurate levels?

A

just before the next dose

115
Q

Most P450 reactions make drugs ___________ which makes them more susceptible for ______________.

A

less hydrophobic making them more susceptible for renal filtration

116
Q

What is autoinduction?

A

When a drug catalyzes its own metabolism

117
Q

What are the most common drug interactions?

A

Inhibition or induction of drug metabolizing enzymes

118
Q

Where does glucuronide metabolism take place?

A

ER- also broad spectrum and inducible like p450

119
Q

What does glucuronide metabolism accomplish?

A

It makes the product more hydrophilic so it can be renally excreted

120
Q

What makes non-microsomal metabolism different from glucuronide and p450 metabolism?

A

It cannot be induced, but it can be competitively inhibited

121
Q

What 5 factors alter drug metabolism?

A
  1. blood flow to the liver
  2. age, sex
  3. disease
  4. drug interactions
  5. genetics
122
Q

Where are most drugs excreted?

What are other options?

A

Kidneys

Lungs, skin, mammary glands

123
Q

What are the four factors to consider for how well a substance will be filtered?

A
  1. glomerular integrity
  2. number of nephrons
  3. size and charge of the molecule
  4. protein binding
124
Q

Molecules under MW ______ can be filtered and under ______ can be filtered well.

A

10,000 filtered, 1000 filtered well

125
Q

The renal tubule can both actively_____ and actively ___ a variety of substates

A

secrete and reabsorb

126
Q

What part of the kidney actively secretes organic acids and bases into the tubular lumen?

A

pars recta (straight part of proximal)

127
Q

The distal nephron is responsible for elimination of what drug? What can compete with this elimination?

A

Digoxin

Competed by: spironolactone, quinidine and verapamil

128
Q

Where does passive reabsorption of weak acids and bases occur?

A

collecting duct

129
Q

What are the two major determinants for passive transport?

A
  1. urine pH

2. flow rate

130
Q

Weak acids are more reasborbed in ______ urine and weak bases are more reabsorbed in _____ urine.

A

acids in acidic pH

bases in basic pH

131
Q

Increased renal flow rate ________ excretion.

What are the two factors that make this true?

A

promotes or increases

  1. increased flow = dilute urine= less conc gradient
  2. less time for diffusion

Fundamentals Block 1 (7 decks)

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