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Apex Review > Pharmacokinetics 3 > Flashcards

Pharmacokinetics 3 Flashcards

1
Q

For most drugs, the rate of metabolism depends on two factors:

A

the concentration of a drug at the site of metabolism
the intrinsic rate of the metabolic process

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2
Q

The concentration of a drug at the site of metabolism is influenced by

A

blood flow to the site of metabolism

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3
Q

The intrinsic rate of the metabolic process is influenced by

A

genetics and enzyme activity

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4
Q

Zero order kinetics describes the situation where there is more

A

drug than enzyme

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5
Q

Examples of drugs that undergo zero order kinetics include

A

aspirin, phenytoin, alcohol, warfarin, heparin, and theophylline

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6
Q

First order kinetics describes the situation where there is

A

less drug than enzyme (no saturation occurs)

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7
Q

Which drugs follow first order kinetics?

A

nearly all the drugs we administer

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8
Q

If an enzymatic pathway that obeys first order kinetics becomes saturated, then the kinetics can

A

change from first order to zero order

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9
Q

Which process is a phase 2 reaction?
a. reduction
b. conjugation
c. oxidation
d. hydrolysis

A

B. conjugation

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10
Q

Drug metabolism is divided into

A

three phases

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11
Q

Phase 1 of drug metabolism includes

A

modification (oxidation, reduction, and hydrolysis)

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12
Q

Phase 2 of drug metabolism includes

A

conjugation

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13
Q

Phase 3 of drug metabolism includes

A

excretion

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14
Q

Sites of metabolism include

A

the kidneys, plasma, lung, and intestines

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15
Q

The ______ is the primary metabolic organ

A

liver

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16
Q

________ is the enzymatic process of altering a molecule’s chemical structure

A

metabolism

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17
Q

The purpose of metabolism is to change a

A

lipid-soluble, pharmacologically active compound into a water-soluble, pharmacologically inactive byproduct

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18
Q

Describe oxidation.

A

removes electrons from a compound

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19
Q

Describe reduction.

A

adds electrons to a compound

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20
Q

Describe hydrolysis.

A

adds water to a compound to split it apart (usually an ester)

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21
Q

A phase 2 reaction

A

conjugates a highly polar, water-soluble substrate to the molecule

22
Q

A phase 3 reaction involves

A

ATP dependent carrier proteins that transport a drug across a cell membrane

23
Q

Describe enterohepatic circulation.

A

some conjugated compounds are excreted in the bile, reactivated in the intestine, and then reabsorbed into the systemic circulation

24
Q

What drugs undergo enterohepatic circulation?

A

diazepam and warfarin

25
Q

Identify the drugs that undergo perfusion-dependent hepatic elimination. select 3
a. diazepam
b. fentanyl
c. rocuronium
d. lidocaine
e. propofol
f. remifentanil

A

fentanyl (b)
lidocaine (d)
propofol (e)

26
Q

Drugs that undergo capacity-dependent hepatic elimination include

A

diazepam & rocuronium

27
Q

Hepatic clearance is the product of

A

liver blood flow and hepatic extraction ratio

28
Q

The extraction ratio is a measure of how much

A

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

29
Q

An extraction ratio of 1.0 means that

A

100% of the drug delivered to the clearing organ is removed

30
Q

An extraction ratio of 0.5 means that

A

50% of the drug delivered to the clearing organ is removed

31
Q

For a drug with a high hepatic extraction ratio (>0.7), clearance is dependent on

A

liver blood flow

32
Q

Examples of drugs where clearance is dependent on liver blood flow include

A

fentanyl, sufentanil, morphine, ketamine, and propofol

33
Q

For a drug with a low hepatic extraction ratio (<0.3), clearance is dependent on

A

the ability of the liver to extract the drug from the blood

34
Q

Examples of drugs where clearance is dependent on the ability of the liver to extract the drug from the blood inlcude

A

rocuronium, diazepam, and methadone

35
Q

When administered orally, high extraction ratio drugs are subject to

A

first-pass metabolism

36
Q

Hepatic extraction ratio is

A

how much drug is removed by the liver

37
Q

The extraction ratio is a measure of

A

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

38
Q

The extraction ratio equation is

A

Extraction ratio= (arterial concentration- venous concentration)/arterial concentration

39
Q

Hepatic clearance is categorized as

A

perfusion-dependent elimination or capacity-dependent elimination

40
Q

Increased liver blood flow leads to

A

increased clearance

41
Q

Does hepatic enzyme activity have an effect on drugs that have perfusion-dependent elimination?

A

No

42
Q

Does hepatic enzyme activity have an affect on drugs that undergo capacity-dependent elimination?

A

Yes! - changes in hepatic enzyme activity or protein binding have a profound impact on the clearance of these drugs

43
Q

Do alterations in liver blood flow affect clearance for capacity dependent elimination drugs?

A

minimally because only a small amount of drug is removed per unit time

44
Q

If enzyme induction occurs, how does this affect capacity-dependent drugs?

A

it increases clearance

45
Q

Drugs with low hepatic extraction ratios include

A

rocuronium
diazepam
lorazepam
methadone
thiopental
theophylline
phenytoin

46
Q

Drugs with intermediate hepatic extraction ratios include

A

midazolam
vecuronium
alfentanil
methohexital

47
Q

Drugs with high hepatic extraction ratios include

A

fentanyl
sufentanil
morphine
meperidine
naloxone
ketamine
propofol
lidocaine
bupivacaine
metoprolol
propranolol
alprenolol
nifedipine
diltiazem
verapamil

48
Q

Enterohepatic circulation describes

A

a process where the liver excretes a substance into the bile, and then that substance is reabsorbed from the small intestine and transported back to the liver

49
Q

Drugs that undergo enterohepatic circulation tend to

A

have a long duration of effect

50
Q

What drugs undergo enterohepatic circulation?

A

diazepam, warfarin

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