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FRCA Pharmacology > Pharmakokinetics > Flashcards

Pharmakokinetics Flashcards

1
Q

With regard to exponential processes:
T/F
When considering a volatile anaesthetic ash-in curve, the rate of increase of the function decreases with time

A

True
With a volatile anaesthetic wash-in curve the FA/FI ratio (ratio of alveolar concentration/inspired concentration) is plotted against time. As time passes, the graph flattens as the alveolar and inspired concentrations equilibrate. Therefore the gradient of the graph reduces with time and consequently the rate of increase of the function decreases.

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2
Q

With regard to exponential processes:
T/F
Nitrogen washout during pre-oxygenation mist closely fits a linear process

A

False

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3
Q

With regard to exponential processes:
T/F
Bacterial growth is an example of an exponential tear-away function

A

True

Bacterial growth starts slowly and rapidly ‘takes off’ in an increasing exponential way - it is a ‘tear away’ function.

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4
Q

With regard to exponential processes:
T/F
When charging a capacitor, the graph of current versus time is similar to a volatile anaesthetic wash-in curve

A

False
When a capacitor charges, the charge versus time and the voltage versus time graphs resemble the wash-in curves. But, with respect to current, as charging proceeds less electrons are required to attempt to complete the charge and the current therefore falls. The current versus time graph therefore resembles a drug elimination curve.

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5
Q

In mathematics, with regard to exponential functions:
T/F
The term natural is used when the scaling uses base 2

A

False
The number e is the natural exponential because it arises naturally in mathematics and physical sciences, i.e. ‘real life’ situations. When the term natural is used, the base is e or 2.718.

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6
Q

In mathematics, with regard to exponential functions:
T/F
A natural exponential function can be transformed to give a straight line by usung any logarithmic transform

A

False

Natural exponential processes need natural logarithmic transforms to produce straight line graphs.

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7
Q

In mathematics, with regard to exponential functions:
T/F
Eulers number is 7.218

A

False

Euler’s number is 2.718

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8
Q

In mathematics, with regard to exponential functions:
T/F
They describe processes where a variable changes at a rate proportional to how long the process has been in operation

A

False
Natural exponential functions describe processes where the variable changes at a rate proportional to its own magnitude, not to time.

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9
Q

In mathematics, with regard to exponential functions:
T/F
A rectangular hyperbola is a special type of exponential function

A

False
Rectangular hyperbolae are conic sections and exponential functions model natural processes; look again at the graphs in the session and compare their features.

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10
Q

With regard to exponential processes:
T/F
They are useful when considering the mechanisms of physiological action potentials

A

True. Many of the processes surrounding the action potential relate to the difference in charges across the membrane and the capacitance of the cell; they are exponential.

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11
Q

Regarding the time constant, the rate constant and half-life:
T/F
The time constant, tau, is the time taken for the initial value to fall by e

A

False. The time constant is the time to fall to 1/e or 1/eth of the original value.

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12
Q

Regarding the time constant, the rate constant and half-life:
T/F
The half-life is never longer than the time constant

A

True. Since the half-life is the time to fall to 50% of the original value and time constant is the time to fall to 37% of the original value , the time constant must be greater.

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13
Q

Regarding the time constant, the rate constant and half-life:
T/F
The rate constant never has any units

A

False. The clue is in the phrase ‘rate constant’, the units must therefore be the units of rate i.e. per second (S-1).

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14
Q

Regarding the time constant, the rate constant and half-life:
T/F
The half-life is half the time constant

A

False. The half-life is 0.693 Tau i.e. roughly 2/3 of the time constant

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15
Q

Regarding the time constant, the rate constant and half-life:
T/F
It is necessary to know both the rate constant and the time constant to be able to plot an accurate graph of the function

A

False. You only need one of the constants to describe the graph, they are all mathematically related.

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16
Q

Regarding τ, k and t1/2:
T/F
τ is the time taken for the initial value to fall by e

A

False. τ is the time to fall to 1/e or 1/eth of the original value. Go back to page 20 for the three definitions.

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17
Q

Regarding τ, k and t1/2:
T/F
t1/2 is never longer than the time constant

A

True. Since t1/2 is the time taken to fall to 50% of the original value and τ is the time taken to fall to 37% of the original value, τ must be greater

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18
Q

Regarding τ, k and t1/2:
T/F
k never has any units

A

False. The clue is in the phrase ‘rate constant’, the units must be the units of rate i.e. per second (S-1).

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19
Q

Regarding τ, k and t1/2:
T/F
t1/2 is half of τ

A

False. The t1/2 is 0.693 τ i.e. roughly 2/3 of τ.

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20
Q

Regarding τ, k and t1/2:
T/F
It is necessary to know both k and τ to be able to plot an accurate graph of the function

A

False. You only need one of the constants to describe the graph, they are all mathematically related.

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21
Q

With regard to exponential drug elimination:
T/F
37% of the process is complete in one τ

A

False. The process is 63% complete in one τ

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22
Q

With regard to exponential drug elimination:
T/F
A bigger k describes a steeper fall in concentration

A

True. A bigger k describes a bigger slope/height ratio for the graph i.e. a steeper fall

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23
Q

With regard to exponential drug elimination:
τ is equal to t1/2 x 0.693
T/F

A

False. It is the other way round. t1/2 = 0.693 x τ.

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24
Q

With regard to exponential drug elimination:
T/F
t1/2 is directly proportional to k

A

False. t1/2 is inversely proportional k.

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25
Q

With regard to exponential drug elimination:
T/F
After three x τ the process is 95% complete

A

True. After one τ a process is 63% complete.
After two τ 63% + 63% of the 37% which remains = 86.3% complete.
After three τ 86.3% + 63% of the 13.7% which remains = 94.9% complete.

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26
Q

With regard to exponential drug elimination:
T/F
Taking logarithms of the time axis transforms the graph into a straight line

A

False. To achieve a straight line, you take natural logarithms of the concentration axis, not the time axis.

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27
Q

With regard to exponential drug elimination:
T/F
τ is the reciprocal of the elimination k

A

True. τ and elimination k are inversely related; if you plot τ against k you get a rectangular hyperbola.

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28
Q

With regard to exponential drug elimination:
T/F
τ is the time taken for the variable to reach 1/e of its initial value

A

True. This is one of the three definitions given; the other two are to reach 37% of original value or the initial concentration’s tangential intersection with the time axis.

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29
Q

With regard to exponential drug elimination:
T/F
Three t1/2 is the time required for the variable to fall to 12.5% of its original value

A

True. In one t1/2 the variable falls to half. In two t1/2 the variable falls by 50% + 50% of 50% = 75%. In three t1/2 the variable falls by 75% + 50% of 25% = 87.5% which leaves only 12.5% of the original concentration.

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30
Q

With regard to exponential drug elimination:
T/F
The graph shows asymptotes on both axes

A

False. There is only a single asymptote which is to the Time axis.

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31
Q

Regarding drug clearance
T/F
It is the volume of plasma that is cleared of a drug per unit time

A

True. This is the definition.

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32
Q

Regarding drug clearance
T/F
Correct units include ml/kg/min and litre/min

A

True. The units of clearance are ‘volume per time’ or, if looking at clearance per kg body weight, then ‘volume per time per kg’.

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33
Q

Regarding drug clearance
T/F
It cannot be greater than liver blood flow

A

False. For drugs that have some extra-hepatic metabolism such as propofol, this can occur

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34
Q

Regarding drug clearance
T/F
It is closely related to t1/2

A

False. Cl is determined by both Vd and the shape of the elimination curve for the drug

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35
Q

Regarding drug clearance
T/F
It is the volume of distribution divided by the τ

A

True. This is one of definitions.

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36
Q

Regarding the volume of distribution
T/F
The initial Vd for propofol is large

A

True. The initial Vd of propofol is variously described by the different models, Schnider 4.27 L and Marsh 15.9 L.

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37
Q

Regarding the volume of distribution
T/F
The Vd of a drug can be greater than the volume of the body

A

True. Vd is a virtual concept, it can be much larger than body volume - see diagram on Marsh model.

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38
Q

Regarding the volume of distribution
T/F
Vd = Cl/elimination k

A

False. This is a way of showing how clearance links Vd and the exponential wash out curve

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39
Q

Regarding the volume of distribution
T/F
Correct units include kg/litre and litres

A

False. Units must be units of volume or in scientific papers, units of volume/kg of body mass - the first of these units is the ‘wrong way round’.

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40
Q

Regarding the volume of distribution
T/F
It can be calculated by using a drug infusion if the half-life and steady state drug concentration is known

A

True. You do not need to know t1/2 for this method and do need to know Cl.

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41
Q

The rate of drug absorption from the stomach is:

lower for fentanyl than diclofenac

A

True

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42
Q

The rate of drug absorption from the stomach is:

greater for weak acids than weak bases for drugs with a pKa of 6

A

True

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43
Q

The rate of drug absorption from the stomach is:

increased in the presence of metoclopromide

A

False

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44
Q

The rate of drug absorption from the stomach is:

always increased by omeprazole

A

False

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45
Q

The rate of drug absorption from the stomach is:

less important than absorption from the small intestine for most oral medication

A

True

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46
Q

When considering absorption of drugs from the GI tract:

fentanyl is better absorbed from the small intestine than the stomach

A

True

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47
Q

When considering absorption of drugs from the GI tract:

thiopental cannot be given through the GI tract route

A

False

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48
Q

When considering absorption of drugs from the GI tract:

atracurium cannot be given orally

A

True

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49
Q

When considering absorption of drugs from the GI tract:

neostigmine is better absorbed than physostigmine

A

False

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50
Q

When considering absorption of drugs from the GI tract:

ketoconazole absorption is increased in patients taking omeprazole

A

False

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51
Q

Which of the following drugs bind more to alpha-1 acid glycoprotein than to albumin?
diazepam

A

False

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52
Q

Which of the following drugs bind more to alpha-1 acid glycoprotein than to albumin?
fentanyl

A

True

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53
Q

Which of the following drugs bind more to alpha-1 acid glycoprotein than to albumin?
phenytoin

A

True

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54
Q

Which of the following drugs bind more to alpha-1 acid glycoprotein than to albumin?
ibuprofen

A

False

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55
Q

Which of the following drugs bind more to alpha-1 acid glycoprotein than to albumin?
lidocaine

A

True

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56
Q

Which of the following are true of plasma protein binding of therapeutic drugs?
Displacement of protein-bound drug by a second drug will necessarily cause toxic effects

A

False

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57
Q

Which of the following are true of plasma protein binding of therapeutic drugs?
Drugs with a low hepatic extraction ratio and high degree of protein binding are most affected by changes in protein binding

A

True

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58
Q

Which of the following are true of plasma protein binding of therapeutic drugs?
Drugs that show flow-dependent hepatic extraction are unaffected by changes in protein binding

A

True

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59
Q

Which of the following are true of plasma protein binding of therapeutic drugs?
The interaction between amiodarone and wafarin is entirely due to competition for plasma protein binding sites

A

False

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60
Q

Which of the following are true of plasma protein binding of therapeutic drugs?
The renal filtration of a drug is increased when plasma protein binding is decreased

A

True

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61
Q

Regarding the distribution of the drugs through the body:

the volume of dstribution at steady state for a drug is dependent only on its lipid solubility

A

False

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62
Q

Regarding the distribution of the drugs through the body:

in a one-compartment model, volume of distribution is directly proportional to drug clearance

A

True

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63
Q

Regarding the distribution of the drugs through the body:

drugs with greater than 95% protein binding have a realtively small volume of distribution

A

False

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64
Q

Regarding the distribution of the drugs through the body:

volume of distribution at a steady state is approximately equal to total body water for most drugs

A

False

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65
Q

Regarding the distribution of the drugs through the body:

Non-depolarising muscle relaxants have smaller volume of distribution than induction agents

A

True

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66
Q

Which of the following describe the distribution of propofol?
It has a volume of distribution of approximately 1.4L/Kg

A

False

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67
Q

Which of the following describe the distribution of propofol?
It is an acidic drug so binds albumin in plasma

A

True

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68
Q

Which of the following describe the distribution of propofol?
The volume of distribution is very large as it is essentially unionized at plasma pH

A

True

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69
Q

Which of the following describe the distribution of propofol?
the initial volume of distribution in adults is age-dependant

A

False

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70
Q

Which of the following describe the distribution of propofol?
The volume of distribution is high because propofol is highly protein bound

A

False

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71
Q

Which of the following are metabolites of atracurium?

cisatracurium

A

False

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72
Q

Which of the following are metabolites of atracurium?

desmethylatracurium

A

False

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73
Q

Which of the following are metabolites of atracurium?

laudanosine

A

True

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74
Q

Which of the following are metabolites of atracurium?

3,17-dihydroxy atracurium

A

False

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75
Q

Which of the following are metabolites of atracurium?

a monoquarternary alcohol derivative

A

True

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76
Q

Which of the following enzymes demonstrate important pharmacogenetic variation?
CYP2E1

A

False

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77
Q

Which of the following enzymes demonstrate important pharmacogenetic variation?
CYP2D6

A

True

78
Q

Which of the following enzymes demonstrate important pharmacogenetic variation?
CYP3A5

A

False

79
Q

Which of the following enzymes demonstrate important pharmacogenetic variation?
CYP2C9

A

Trua

80
Q

Which of the following enzymes demonstrate important pharmacogenetic variation?
CTP1A2

A

False

81
Q

Which of the following drugs have an oral bioavailability of more than 75%?
Aspirin

A

False

82
Q

Which of the following drugs have an oral bioavailability of more than 75%?
Paracetamol

A

True

83
Q

Which of the following drugs have an oral bioavailability of more than 75%?
Oramorph

A

False

84
Q

Which of the following drugs have an oral bioavailability of more than 75%?
diclofenac

A

False

85
Q

Which of the following drugs have an oral bioavailability of more than 75%?
ibuprofen

A

True

86
Q

Which of the following routes of elimination are the major route of the named drug?
lungs, sevoflurane

A

True

87
Q

Which of the following routes of elimination are the major route of the named drug?
renal, benzylpenicillin

A

True

88
Q

Which of the following routes of elimination are the major route of the named drug?
red cell esterases, esmolol

A

True

89
Q

Which of the following routes of elimination are the major route of the named drug?
tissue esterases, remifentanil

A

True

90
Q

Which of the following routes of elimination are the major route of the named drug?
non-enzymatic plasma degradation, mivacurium

A

False

91
Q

In a one-compartment model for the kinetics of a drug:

The volume of distribution at steady state can be calculated using a single bolus dose of drug

A

True

92
Q

In a one-compartment model for the kinetics of a drug:

if volume of distribution stays the same, clearance increases if the time constant increases

A

True

93
Q

In a one-compartment model for the kinetics of a drug:

the context sensitive half life is proportional to the duration of an infusion

A

False

94
Q

In a one-compartment model for the kinetics of a drug:

After giving an IV bolus dose, the rate of elimination at a particular time is dependent only on the clearance

A

False

95
Q

In a one-compartment model for the kinetics of a drug:

the behaviour of the drug can be predicted as long as the clearance is known

A

False

96
Q

If a drug given by continuous IV infusion behaves according to a 3 compartment model:
The volume of distribution at a steady state is the most important determinant of the variability of the context sensitive half time

A

False

97
Q

If a drug given by continuous IV infusion behaves according to a 3 compartment model:
the second compartment has 3 rate constants associated with it

A

False

98
Q

If a drug given by continuous IV infusion behaves according to a 3 compartment model:
it the plasma level has reached steady state, then clearance out of the body can be calculated from the infusion rate and concentration

A

True

99
Q

If a drug given by continuous IV infusion behaves according to a 3 compartment model:
drug can be removed from the system from any of the 3 compartments

A

False

100
Q

If a drug given by continuous IV infusion behaves according to a 3 compartment model:
the effect compartment equilibrates with the central compartment

A

True

101
Q

When considering elimination of drug from the body:

the rate of elimination is equal to the clearance

A

False

102
Q

When considering elimination of drug from the body:

if glomerular filtration rate doubles, then the amount of free drug excreted through urine also doubles

A

False

103
Q

When considering elimination of drug from the body:

CYP450 enzymes are found only in hepatocytes

A

False

104
Q

When considering elimination of drug from the body:

hepatic enzymes involved in xenobiotic metabolism are exclusively associated with the smooth endoplasmic reticulum

A

False

105
Q

When considering elimination of drug from the body:

more than 99% of the drug will have been eliminated after 3 half lives

A

False

106
Q

For a simple one-compartment model:

The half life is longer than the time contant

A

False

107
Q

For a simple one-compartment model:

the rate constant for elimination is found from the slope of the graph that plots log(concentration) against time

A

True

108
Q

For a simple one-compartment model:

the clearance is the ratio of the volume of distribution to the time constant

A

True

109
Q

For a simple one-compartment model:
The volume of distribution multiplied by the rate constant for elimination divided by plasma concentration is equal to the clearance

A

False

110
Q

For a simple one-compartment model:
The shape of the curve that describes the rise of drug concentration with time on starting a constant rate infusion is a negative exponential

A

True

111
Q

In patients with hepatic failure and ascites

The volume of distribution for hydrophilic drugs is reduces

A

False

112
Q

In patients with hepatic failure and ascites

the metabolism of all drugs is reduced

A

False

113
Q

In patients with hepatic failure and ascites

The bioavailability of drugs with a moderate hepatic extraction ratio is increased

A

True

114
Q

In patients with hepatic failure and ascites

The terminal elimination half-life for remifentanil is unaffected

A

True

115
Q

In patients with hepatic failure and ascites

the dose of non-depolarising muscle relaxants required for intubation is increased

A

True

116
Q

Which of the following will increase hepatic extraction of propofol?
dobutamine

A

True

117
Q

Which of the following will increase hepatic extraction of propofol?
ciprofloxacin

A

False

118
Q

Which of the following will increase hepatic extraction of propofol?
carbamezepine

A

False

119
Q

Which of the following will increase hepatic extraction of propofol?
noradrenaline

A

False

120
Q

Which of the following will increase hepatic extraction of propofol?
Chronic alcohol intake

A

False

121
Q

A mammilary 3 compartment model used to model effect-site targeting of drug concentration
elimination occurs from the effect sire

A

False

122
Q

A mammilary 3 compartment model used to model effect-site targeting of drug concentration
the volume of the effect site is not included in the volume of distribution at steady state

A

True

123
Q

A mammilary 3 compartment model used to model effect-site targeting of drug concentration
there are two inter-compartmental clearances included in the model

A

True

124
Q

A mammilary 3 compartment model used to model effect-site targeting of drug concentration
the t1/2keo describes the rate of equilibration between plasma and effect compartments

A

True

125
Q

A mammilary 3 compartment model used to model effect-site targeting of drug concentration
clearance from the system can be found from steady state infusion rate and plasma concentration

A

True

126
Q

When measuring bioavailability:

drug behaviour must be fitted to a known model in order to calculate bioavailability

A

False

127
Q

When measuring bioavailability:

bioavailability refers only to oral compared with IV administration

A

False

128
Q

When measuring bioavailability:
oral bioavailability can be found by dividing clearance of the drug when given orally by the clearance found when given IV

A

False

129
Q

When measuring bioavailability:

The same dose of drug must be given orally and IV to find oral bioavailability

A

True

130
Q

When measuring bioavailability:

interindividual variability must be expected

A

True

131
Q

Which of the listed drugs have a volume of distribution at steady state grater then total body water?
cisatracurium

A

False

132
Q

Which of the listed drugs have a volume of distribution at steady state grater then total body water?
neostigmine

A

False

133
Q

Which of the listed drugs have a volume of distribution at steady state grater then total body water?
Atropine

A

True

134
Q

Which of the listed drugs have a volume of distribution at steady state grater then total body water?
noradrenaline

A

False

135
Q

Which of the listed drugs have a volume of distribution at steady state grater then total body water?
sevoflurane

A

True

136
Q

Which of the following drugs readily cross the placenta?

S-bupivicaine

A

True

137
Q

Which of the following drugs readily cross the placenta?

diazepam

A

True

138
Q

Which of the following drugs readily cross the placenta?

fentanyl

A

True

139
Q

Which of the following drugs readily cross the placenta?

succinylcholine

A

False

140
Q

Which of the following drugs readily cross the placenta?

isoflurane

A

True

141
Q

The following are true regarding Volume of Distribution (Vd):
It is the amount of drug that distributes following administration

A

False. It is the volume that a drug distributes into following administration.

142
Q

The following are true regarding Volume of Distribution (Vd):
Can be greater than total body water

A

True. TBW = 42L whilst Vd can be up to 1000L.

143
Q

The following are true regarding Volume of Distribution (Vd):
Is measured in kg/L

A

False. It is measured in L/Kg.

144
Q

The following are true regarding Volume of Distribution (Vd):
Is a constant for a given drug

A

True

145
Q

The following are true regarding Volume of Distribution (Vd):
The following are true regarding Volume of Distribution (Vd):

A

False. Vd = Clearance x Time Constant.

146
Q

Context sensitive half-time:

Is a decrement time

A

True. Decrement time = the time taken of the plasma level for a drug to fall to a specified value (Context-Sensitive Half-Time is 50%).

147
Q

Context sensitive half-time:

Shares a constant relationship with elimination half-life

A

False. There is no such relation.

148
Q

Context sensitive half-time:

Varies with duration of drug infusion

A

True. This is the ‘context’.

149
Q

Context sensitive half-time:

Is reliably used to describe time for recovery

A

False. It is the time for the plasma levels to fall to 50% of the value when the infusion is stopped.

150
Q

Context sensitive half-time:

Reflects the combined effects of absorption and distribution

A

False. It reflects the combined effects of distribution and metabolism.

151
Q

The following influence Volume of Distribution (Vd):

Regional blood flow

A

True

152
Q

The following influence Volume of Distribution (Vd):

Lipid solubility

A

True

153
Q

The following influence Volume of Distribution (Vd):

Degree of tissue protein binding

A

True

154
Q

The following influence Volume of Distribution (Vd):

Degree of plasma protein binding

A

True

155
Q

The following influence Volume of Distribution (Vd):

Degree of ionisation

A

True

156
Q

Infusion kinetics:

It takes 5 half-times to reach steady state concentration

A

False. It takes 5 Half-lives to reach steady state concentration.

157
Q

Infusion kinetics:

Steady state volume of distribution is dependent on lipid solubility and molecular weight

A

False. Steady state volume of distribution is dependent on lipid solubility and clearance.

158
Q

Infusion kinetics:

Loading Dose = Vd x Desired Plasma Concentration

A

True

159
Q

Infusion kinetics:

Maintenance Dose = Steady State Vd x Clearance

A

False. Maintenance Dose = Steady State Concentration x Clearance.

160
Q

Infusion kinetics:

Clearance = Input (mg/min) x Plasma Concentration (mg/ml)

A

False. In infusion kinetics at steady state Input = Elimination

Input (mg/min) is therefore equal to Clearance (ml/min) x Plasma Concentration (mg/min)

Therefore:

Clearance = Input (mg/min) / Plasma Concentration (mg/ml)

161
Q

The following statements are true of Cytochrome P450 enzyme isoforms:
CYP2E1 is involved in metabolism of paracetamol

A

True

162
Q

The following statements are true of Cytochrome P450 enzyme isoforms:
CYP3A4 is involved in metabolism of phenytoin

A

False. CYP3A4 is important in the metabolism of both midazolam and alfentanil.

163
Q

The following statements are true of Cytochrome P450 enzyme isoforms:
Are only found in the liver

A

False. CYP2E1 is found in the kidneys.

164
Q

The following statements are true of Cytochrome P450 enzyme isoforms:
Account for most phase 2 reactions

A

False. Account for most phase 1 reactions.

165
Q

The following statements are true of Cytochrome P450 enzyme isoforms:
CYP2E1 is involved in the metabolism of chloride containing volatile agents

A

False. CYP2E1 is involved in the metabolism of fluoride containing volatile agents.

166
Q

The following are enzyme inducers:

Rifampicin

A

True

167
Q

The following are enzyme inducers:

Metronidazole

A

False it is an enzyme inhibitor

168
Q

The following are enzyme inducers:

Acute alcohol use

A

False. Acute alcohol use inhibits whilst chronic use induces.

169
Q

The following are enzyme inducers:

Carbemazepine

A

True

170
Q

The following are enzyme inducers:

Chloramphenicol

A

False. It is an enzyme inhibitor.

171
Q

Phase 2 reactions include:

Oxidation

A

False. This is a Phase I reaction.

172
Q

Phase 2 reactions include:

Acetylation

A

True

173
Q

Phase 2 reactions include:

Sulphation

A

True

174
Q

Phase 2 reactions include:

Hydrolysis

A

False. This is a Phase I reaction.

175
Q

Phase 2 reactions include:

Glucuronidation

A

True

176
Q

Elimination:

Can only be by either distribution or metabolism

A

False. Can also be by excretion.

177
Q

Elimination:

In 1st order kinetics, half-life is constant

A

True

178
Q

Elimination:

In 1st order kinetics, a constant amount of drug is eliminated per unit time

A

False. A constant proportion is eliminated per unit time.

179
Q

Elimination:

Zero order kinetics is a linear process

A

False. Zero order kinetics is also known as non-linear kinetics.

180
Q

Elimination:

In zero order kinetics, half-life increases with dose administered

A

True

181
Q

Hepatic clearance:

A drug with a high extraction ratio is not affected by protein binding

A

True. It is not affected by enzyme level either.

182
Q

Hepatic clearance:

Lignocaine is an example of an enzyme limited drug

A

False. Lignocaine has a high extraction ratio (>0.7) and is therefore flow / perfusion limited (as opposed to enzyme / capacity limited).

183
Q

Hepatic clearance:

High extraction ratio implies significant 1st pass metabolism

A

True. Most of the drug is extracted on the first pass through the liver, hence why changes in hepatic blood flow can drastically affect clearance.

184
Q

Hepatic clearance:

Enzyme induction / inhibition can profoundly affect the clearance of drugs with a low extraction ratio

A

True. Drugs with a low extraction ratio are enzyme / capacity limited drugs.

185
Q

Hepatic clearance:

Warfarin is an example of an enzyme limited drug

A

True. As are phenytoin, theophylline and most benzodiazepines and barbituates.

186
Q

Bioavailability:

Of drugs administered via the IV route can be as high as 90%

A

False. IV drug administration provides 100% bioavailability.

187
Q

Bioavailability:

Is the fraction of administered drug that reaches systemic circulaiton

A

True

188
Q

Bioavailability:

Glycopyrrolate has >80% bioavailability

A

False. Glycopyrrolates bioavailability is < 5%.

189
Q

Bioavailability:

Is influenced by genetics

A

True. There are phenotypic variations in bioavailability.

190
Q

Bioavailability:

Is influenced by circadian rhythm

A

True

FRCA Pharmacology (13 decks)

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