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1 APEX > Pharmokinetics > Flashcards

Pharmokinetics Flashcards

1
Q

What is the relationship between a drugs dose and the plasma concentration?

A

volume of distribution

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2
Q

What two things does volume of distribution assume?

A
  1. drug distributes instantaneously

2. the drug is not subject to biotransformation or elimination before it fully distributes

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3
Q

How would a drug with a low volume of distribution be described?

A

< 0.6mL/kg or < 42L

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4
Q

Where do drugs with a low Vd distribute?

A

some or all of the body, but not the fat. “hydrophilic”

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5
Q

Does a drug with a low Vd need a larger or smaller dose to achieve a desired plasma concentration?

A

smaller

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6
Q

What is one class of a drugs with a low Vd?

A

NMB

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7
Q

The ____ the Vd the ___ the loading dose to achieve a desired plasma concentration.

A

higher, higher

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8
Q

What is the formula for Vd?

A

Vd= amount of drug / desired plasma concentration

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9
Q

What is the formula used to calculate loading dose?

A

IV loading dose = Vd x (desired plasma concentration / bioavailability)

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10
Q

How would a drug with a high Vd be described?

A

> 0.6L/kg or > 42L

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11
Q

Where do drugs with a high Vd distribute to?

A

into body water and fat. “lipophilic”

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12
Q

Do drugs with a higher Vd need a smaller or larger dose to achieve a desired plasma concentration?

A

higher

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13
Q

What is an example of drug with a high Vd?

A

propofol

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14
Q 
How is TBW distributed?
TBW =
Extracellular=
Intracellular=
Plasma=
Interstitial=
A 
TBW = 42L
Extracellular= 14L
Intracellular= 28L
Plasma= 4L
Interstitial= 10L
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15
Q

What is the volume of plasma that is cleared of drug per unit time?

A

clearance

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16
Q

What are the three major clearing organs?

A

liver
kidney
organ independent (Hoffman elimination and ester hydrolysis in plasma)

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17
Q

What occurs when the amount of drug entering the body equals the amount being eliminated?

A

steady state

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18
Q

How many half lives must occur to reach steady state?

A

5 half lives

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19
Q

What is drug clearance directly proportional to?

A

blood flow to clearing organ
extraction ratio
drug dose

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20
Q

What is drug clearance inversely related to?

A

half life

drug concentration in the central compartment

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21
Q

What describes the alpha phase?

A

distribution of a drug.

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22
Q

What occurs during the alpha phase?

A

the drug rapidly distributes from the central compartment (plasma) to the peripheral compartments (tissues)

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23
Q

What determines the slope of alpha distribution?

A

Volume of distribution

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24
Q

Describe the alpha phase slope of a lipophilic drug.

A

larger volume of distribution, steeper slope

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25
Q

What occurs during the beta phase?

A

eliminiation

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26
Q

As a drug is being eliminated from the central compartment and the plasma concentration declines. What will eventually happen?

A

concentration gradient reverses and drug will redistribute from the tissues back into the central compartment.

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27
Q

Does the beta phase slope represent elimination from the central compartment, peripheral, or both?

A

central

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28
Q

What is the speed at which a reaction occurs? “how fast the molecules move b/w compartment”

A

rate constants

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29
Q

Drug transfer from the central to peripheral compartment is K___

A

K12

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30
Q

Drug transfer from the peripheral to central compartment is K___

A

K21

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31
Q

Drug elimination from the body is K___

A

Ke

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32
Q

The time it takes for 50% of the drug to be removed from the body after IV injection

A

elimination half life

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33
Q

The time it takes for 50% of the drug to be removed from the plasma during the elimination phase (beta phase)?

A

elimination half time

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34
Q

Elimination half times is only applicable to what compartment model?

A

one compartment

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35
Q

What is the time required for the plasma concentration to decline by 50% after infusion is stopped?

A

context sensitive half time

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36
Q

What narcotic is quickly metabolized by plasma esterases, and has a context sensitive half time independent of infusion time?

A

Remifentanil

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37
Q

Arrange Fentanyl, Sufentanil, Remifentanil, and Alfentanil from longest to shortest centext sensitive half time.

A

fentanyl - longest
alfentanil
sufentanil
remifentanil - shortest

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38
Q

What ions are weak acids paired with?

A

sodium, calcium, and magnesium (all positive ions)

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39
Q

What ions are weak bases paired with?

A

chloride, sulfate (all negative)

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40
Q

When pKa and pH are the same, what percentage of the drug will be ionized and nonionized?

A

50%, 50%

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41
Q

What does an acidic drug donate?

A

H+

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42
Q

What does a basic drug donate?

A

OH-

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43
Q

What is the process where a molecule gains a positive or negative electron and this molecular charge affects a molecules ability fo diffuse through lipid membranes.

A

ionization

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44
Q

Describe solubility of ionized and non-ionized drugs.

A

ionized are hydrophilic and lipophobic

nonionized are hydrophobic and lipophilic

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45
Q

Are ionized or nonionized drugs active?

A

nonionized

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46
Q

What type of drugs are more likely to undergo hepatic biotransformation?

A

nonionized

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47
Q

What type of drugs are more likely to undergo renal elimination?

A

ionized

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48
Q

What type of drugs can diffuse across lipid bilayers?

A

nonionized

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49
Q

An acidic drug in a basic solution will be highly ionized or nonionized?

A

ionized

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50
Q

An acidic drug in a acidic solution will be highly ionized or nonionized?

A

nonionized

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51
Q

A basic drug in a acidic solution will be highly ionized or nonionized?

A

ionized

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52
Q

A basic drug in a basic solution will be highly ionized or nonionized?

A

nonionized

53
Q

What circumstance creates the strongest gradient for passage of LA from mother to fetus?

A

maternal alkalosis, fetal acidosis

54
Q

What part of a drug can diffuse across the cell membrane?

A

lipophilic, nonionized

55
Q

What part of a drug can diffuse across the cell membrane?

A

lipophilic, nonionized

56
Q

Can ionized drugs cross cell membranes?

A

no

57
Q

What are the three major plasma proteins?

A

albumin, a1-acid glycoprotein, beta globulin

58
Q

Which plasma proteins bind to basic drugs?

A

a1-acid glycoprotein and beta globulin

59
Q

What plasma protein binds acidic drugs mainly?

A

albumin

60
Q

What is the primary determinant of plasma oncotic pressure?

A

albumin

61
Q

Which plasma protein is a measure of protein synthesis, has a negative charge, and a half life of 2 weeks?

A

albumin

62
Q

What situations cause a decrease in albumin?

A

liver disease, renal disease, old age, malnutrition, pregnancy

63
Q

What increases a1-acid glycoprotein?

A

surgical stress, myocardial infarction, chronic pain, RA, old age

64
Q

What decreases a1-acid glycoprotein?

A

neonates and pregnancy

65
Q

How is % change of a bound and unbound drug calculated?

A

% change = (new unbound value - old unbound value) / new unbound value

66
Q

What causes changes in plasma protein binding?

A

decreased plasma protein content, or competition to binding sites

67
Q

The Vd and plasma protein content have what type of relationship?

A

inverse

68
Q

Is the metabolism and elimination of highly protein bound drugs slower or faster compared to drugs with decreased protein binding?

A

slower

69
Q

What order kinetics is described by a drug being eliminated at a rate of 5mg/h?

A

zero order kinetics

70
Q

When there is more drug than enzyme, the drug is eliminated by which order kinetics?

A

zero order

71
Q

What drugs undergo zero order kinetics?

A

aspirin, phenytoin, alcohol, warfarin, heparin, theophylline

72
Q

A drug that is eliminated at a rate of 50%, undergoes which order kinetics?

A

first order kinetics

73
Q

Is there more enzyme or drug in first order kinetics?

A

more enzyme. the enzyme metabolizes the drug at a constant fraction

74
Q

What are the three phases of drug reactions?

A

phase 1: modification
phase 2: conjugation
phase 3: elimination/excretion

75
Q

What are the most common sites of drug metabolism?

A

liver #1 and plasma

76
Q

The P450 system is located where?

A

smooth endoplasmic reticulum

77
Q

What types of drug metabolism occurs in the plasma?

A

Hoffman elimination, hydrolysis reactions,

78
Q

How does metabolism facilitate drug elimination?

A

metabolism changes a lipid soluble compound into a H20 soluble, inactive byproduct

79
Q

Why does metabolism transform drugs into H2O soluble compounds?

A

H2O soluble drugs have greater ionization, which decreases Vd, increasing delivery to the kidney for elimination

80
Q

What are the three stages of phase 1 reactions?

A

oxidation- removes electrons
reduction- adds electrons
hydrolysis- adds H20 to split apart

81
Q

Most phase 1 reactions are carried out by which system?

A

P450

82
Q

What occurs during conjugation? Phase 2 reactions

A

H20 is added to the molecule. It becomes highly H20 soluble, inactive and ready for elimination

83
Q

What is enterohepatic circulation?

A

Drugs like diazepam are excreted in the bile, reactivated in the intestine, then reabsorbed into circulation

84
Q

What do phase 3 reactions require to transport drugs across cell membranes?

A

ATP dependent carrier proteins

85
Q
A
86
Q

Which drug has higher efficacy?

Which drug needs to occupy fewer receptors to cause a response?

A

Efficacy: A
Response: B

87
Q

Which drug is more potent?

A

Drug A

88
Q

What drugs undergo perfusion dependent hepatic elimination?

A

fentanyl, lidocaine, propofol

89
Q

What two drugs undergo capacity dependent elimination?

A

diazepam and Roc

90
Q

What is the extraction ratio?

A

how much drug is delivered to clearing organ vs how much is removed by that organ.

91
Q

What does an extraction ratio of 1.0 and 0.5 represent?

A

1 means 100% delivered in cleared

0.5 means 50% of drug delivered is cleared

92
Q

What two factors determine hepatic clearance?

A

blood flow and extraction ratio

93
Q

What extraction ratio signifies flow limited extraction?

A

ER > 0.7

94
Q

What extraction ratio signifies capacity limited extraction?

A

ER < 0.3

95
Q

What does an ER > 0.7 mean?

A

clearance is dependent on liver BLOOD FLOW

96
Q

What does an ER < 0.3 mean?

A

clearance is dependent on the livers ability to extraction drug from the blood.

97
Q

What has a significant impact on hepatic clearance if the drug has a ER < 0.3?

A

enzyme activity and protein binding

98
Q

What drugs have an ER < 0.3 so they are enzyme dependent?

A

Rocuronium, Diazepam, Lorazepam, Methadone, Thiopental, Theophylline, Phenytoin

99
Q

What are examples of drugs with an intermediate ER?

A

Versed, Vec, Alfentanil, methohexital

100
Q

What are drugs with a ER > 0.7, blood flow dependent elimination?

A

Fentanyl, Sufentanil, Morphine, Meperidine, Naloxone, Ketamine, Propofol, Lidocaine, Bupivacaine, Metoprolol, Propranolol, Alprenolol, Nifedipine, Diltiazem, Verapamil

101
Q

What is the most important mechanism of drug biotransformation in the body?

A

P450 enzymes

102
Q

Where are P450 enzymes located?

A

hepatocyte smooth ER. Also lungs, skin, kidneys, adrenal gland, and GI tract.

103
Q

What is the most important cytochrome P450 enzyme?

A

CYP 3A4

104
Q

What are the three effects of enzyme inducers?

A

increase clearance, decrease plasma levels, may need higher doses.

105
Q

What are examples of enzyme inducers?

A

tobacco, barbiturates, ethanol, phenytoin, rifampin carbamazepine

106
Q

What do enzyme inhibitors do?

A

compete for binding sites on an enzyme and reduce clearance.

107
Q

What are the three effects of enzyme inhibitors?

A

decrease clearance, increase plasma levels, need smaller doses.

108
Q

What are examples of enzyme inhibitors?

A

grapefruit juice, cimetidine, omeprazole, isoniazid, SSRI’s, erythromycin, ketoconazole

109
Q

What are examples of drugs that undergo metabolism by CYP 3A4?

A

Fentanyl, Alfentanil, Sufentanil, Methadone
Midazolam, Diazepam
Lidocaine, Bupivacaine, Ropivacaine

110
Q

What are examples of drugs that undergo metabolism by CYP 2D6?

A

codeine, oxycodone, hydrocodone

111
Q

What are examples of drugs that undergo metabolism by CYP 1A2?

A

Theophylline

112
Q

What are some CYP 3A4 inhibitors and inducers?

A

inducers: phenytoin, carbamazepine, dexamethasone
inhibitors: isoniazid, SSRI’s, Quinidine

113
Q

What are some CYP 1A2 inhibitors and inducers?

A

inducers: tobacco, cannabis, ethanol
inhibitors: erythromycin, ciprofloxacin

114
Q

What type of drugs are excreted unchanged?

A

hydrophilic

115
Q

What type of drugs must undergo biotransformation before they can be eliminated?

A

lipophilic

116
Q

What drugs are freely filtered at the glomerulus?

A

those not bound to proteins

117
Q

What are the organic anion transporters?

A

furosemide, thiazide diuretics, & penicillin

118
Q

What are the organic cation transporters?

A

morphine, meperidine, & dopamine

119
Q

What determines whether drugs are excreted in the urine or reabsorbed into peritubular capillaries?

A

urine pH

120
Q

How does the pH of the urine determine reabsorption and excretion of drugs?

A

acidic urine reabsorbs acidic drugs, eliminated basic drugs

basic urine reabsorbs basic drugs, eliminated acidic drugs

121
Q

What medications acidify urine and leads to elimination of basic drugs?

A

ammonium chloride and cranberry juice

122
Q

What medications will alkalinize urine and eliminate acidic drugs?

A

sodium bicarbonate and acetazolamide

123
Q

What are the three main metabolic pathways in the plasma?

A

pseudocholinesterase, nonspecific esterases, alkaline phosphatase

124
Q

What metabolic pathway does not involve enzymes?

A

Hoffman elimination

125
Q

Pseudocholinesterase deficiency extends the duration of action of what three drugs?

A

succinylcholine, mivicurium, and ester LA’s (1 “i” in their name)

126
Q

What drugs undergo metabolism by nonspecific esterases?

A

remifentanil, esmolol, etomidate, atracurium

127
Q

What drug undergoes metabolism by nonspecific esterases and hepatic metabolism?

A

etomidate

128
Q

What drug undergoes metabolism by nonspecific esterases and Hoffman elimination?

A

atracurium

129
Q

What medication is converted to a prodrug by alkaline phosphatase?

A

fospropofol

1 APEX (9 decks)

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