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Lindsays Flashcardlet > RE Chapter 6 > Flashcards

RE Chapter 6 Flashcards

0
Q

True or False? The smaller the molecular size of an agent, the better it crosses the lipid barriers and membranes of tissues.

A

True.

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1
Q

Pharmacokinetics Definition

A

The study of changes in the concentration of a drug during the process of absorption, distribution, metabolism, and elimination from the body (what the body does to a drug once the agent has been introduced to the system)

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2
Q

Molecules with molecular weights greater than ____ to ____ do not cross cell membranes.

A

100 to 200

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3
Q

The transfer of drug depends on what 5 things?

A
  1. Molecular Size
  2. Transporters
  3. Lipid solubility
  4. Degree of Ionization
  5. Protein Binding
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4
Q

Active or passive transport does not require energy and involves transfer of drugs from high to low concentrations

A

passive

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5
Q

Active or passive transport is generally faster and requires energy.

A

Active

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6
Q

These drug transporters control passive movement of solutes down their electrochemical gradient.

A

Solute carrier transporters (SLC)

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7
Q

These drug transporters are active pumps requiring energy derived from ATP.

A

adenosine triphosphate-binding cassette (ABC) transporters

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8
Q

What is antiport?

A

The exchange of one molecule for another in a drug transporter

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9
Q

What is symport?

A

Transport of to molecules together in the same direction

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10
Q

Where are SLCs most important?

A

blood-brain barrier, GI tract, renal tubules, biliary tract, placenta

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11
Q

The charged (ionized) form of a drug is…(water or lipid soluble?)

A

water soluble (hydrophillic) - unable to diffuse across cell membranes.

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12
Q

The uncharged (nonionized) form of a drug is…(water or lipid soluble?)

A

Lipid soluble (lipophillic)

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13
Q

True or False? The higher degree of ionization the less access the drug has across tissues.

A

True

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14
Q

How are ionized drugs commonly excreted?

A

Through the RENAL system since they are not absorbed well and may not be metabolized by the liver.

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15
Q

what is the dissociation constant & PH gradient across the membrane?

A

It determines the degree of ionization of an agent

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16
Q

For basic drugs PKa =pH=

A

log[(HA+)/(A-)]

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17
Q

For acidic drugs:

pKa=pH=

A

log[(A-)/(HA+)]

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18
Q

Acids are proton _____(acceptors/donors) and bases are proton ______(acceptors/donors)

A

Acids - proton donors

Bases - proton acceptors

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19
Q

If a weak acid is placed in a pH below its pKa is the drug ionized or nonionized?

A

nonionized (so lipid soluble)

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20
Q

if a weak base is placed in an environment below its pKa does it become ionized or nonionized?

A

ionized (lipid insoluble)

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21
Q

Weak acids:

  1. pH > pKa - (ionized/equal/nonionized)
  2. pH = pKa - (ionized/equal/nonionized)
  3. pH < pKa - (ionized/equal/nonionized)
A
  1. Ionized form is predominant
  2. Equal forms exist
  3. Nonionized form is predominant
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22
Q

Weak Bases:

  1. pH > pKa - (ionized/equal/nonionized)
  2. pH = pKa - (ionized/equal/nonionized)
  3. pH < pKa - (ionized/equal/nonionized)
A
  1. Nonionized predominant
  2. Nonionized equal to ionized
  3. Ionized predominant
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23
Q

What are situations when there is reduced plasma proteins?

A

liver/kidney disease, poor nutrition, the last trimester of pregnancy

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24
Q

What protein favors binding to acidic drugs?

A

albumin

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25
Q

What proteins favor binding to basic drugs?

A

alpha1-acid glycoprotein (AAG) & beta-globlulin

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26
Q

What protein binds to cyclosporine?

A

lipoprotiens

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27
Q

What protein binds to corticosteroids?

A

transcortin

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28
Q

Degree of protein binding is proportional to _______.

A

lipid solubility

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29
Q

Drugs with protein binding _____% are conceptualized to have an unexpected intensification of their effect if they are displaced from plasma proteins.

A

> 90

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30
Q

Drugs with _____% protein binding have so little change in free active fractions that they are not a concern.

A

<90

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31
Q

When entereally administered acidic drugs are absorbed in the ______ wheras basic drugs are absorbed in the ______

A

stomach

intestine

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32
Q

What is the definition of presystemic elimination?

A

the elimination of drug by the GI system before the drug reaches systemic circulation

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33
Q

What are the three mechanisms of presystemic elimination?

A
  1. stomach acids hydrolyze the drug
  2. enzymes in the GI wall deactivate the drug
  3. liver biotransforms ingested drug before it reaches the effective sites (first pass metabolism)
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34
Q

Which route of administration has the most rapid onset and greatest bioavailability?

A

Intravenous.

Inhalation also parallels IV administration

35
Q

Which route of administration has the slowest absorption?

A

Topical

36
Q

Name some agents that undergo substantial first-pass elimination

A
  • Aspirin
  • glyceryl trinitrate
  • Isosorbide dinitrate
  • Levodopa
  • Lidocane
  • Metoprolol
  • Morphine
  • propanolol
  • salbutamol
  • verapamil
37
Q

Which drug routes is the drug rapidly delivered tot he superior vena cava for transport to the effect site?

A

Sublingual/buccal

38
Q

Drugs placed in the _____ rectum are absorbed into the portal system via superior hemorrhoidal vein and undergo significant first-pass effect

A

proximal

39
Q

Drugs placed in the ______ rectum do not undergo pre-systemic elimination and have a more predictable response.

A

Distal

40
Q

What is the definition of bioavailability?

A

The extent to which a drug reaches its effect site after its introduction into the circulatory system.

41
Q

What are the main factors that determine the rate of passive diffusion across membranes?

A

Lipid solubility and concentration gradient.

42
Q

The central compartment (vessel rich group) consists of what? It represents ____% of body mass and receives _____% of cardiac output.

A
  • heart, lungs, liver, kidneys
  • 10%
  • 75%
43
Q

The peripheral compartment (vessel poor group) consists of what? It represents ____% of body mass and receives _____% of cardiac output.

A
  • muscle, fat, bone
  • 90%
  • 25%
44
Q

What is the equation for volume of distribution?

A

volume of distribution = dose of drug / plasma concentration of drug

45
Q 
In a 70 kg patient what is the volume for:
plasma compartment?
interstitial compartment?
extracellular compartment?
intracellular fluid?
A

plasma: 4 liters
interstitial: 10 liters
extracellular: 14 liters (plasma + intersitital)
intracellular: 28 liters

46
Q

What is total body water volume for a 70 kg patient?

A

42 liters (plasma + interstitial + ICF)

47
Q

What is the typical volume of distribution for a 70 kg patient?

A

42L/70kg = 0.6L/kg

48
Q

Drugs with a high volume of distribution are considered to be ______(lipid/water soluble) and drugs with a low volume of distribution are considered to be ______(lipid/water soluble)

A 
large Vd (>0.6L/kg): lipid soluble
small Vd(<0.4L/kg): water soluble
49
Q

What does the alpha phase of the plasma concentration curve represent?

A

The distribution phase, the initial dispersal of drug into the tissue compartments from the central compartment.

50
Q

What does the beta phase of the plasma concentration curve represent?

A

Elimination phase, elimination of the drug from the circulation

51
Q

What phase of the plasma concentration curve is used to determine elimination half-life of drugs?

A

beta phase

52
Q

What is a biexponential decay curve?

A

When two components of decay exist such as in the plasma concentration curve. The first slope describes distribution and the second describes elimination.

53
Q

What is the goal of metabolism?

A

To change lipid soluble agents into more water soluble forms so the kidneys can eliminate them from the body.

54
Q

What is first order kinetics?

A

Drugs leave the body at a constant rate or percentage over time. The half-life is constant. Dose is independent of clearance.

55
Q

What is zero order kinetics?

A

Even at therapeutic doses drugs exceed the body’s ability to excrete or metabolize them, the enzymes that eliminate them are saturated.

56
Q

What are phase I reactions?

A

Oxidation, reduction, and hydrolysis

57
Q

What is oxidation?

A

Oxygen is introduced to the molecule, loss of electrons.

58
Q

What is reduction?

A

Involves the gain of electrons. Insufficient oxygen is present to compete for electrons so enzymes transfer electrons directly to substrate.

59
Q

What enzymes catalyze oxidation and reduction?

A

Cytochrome P-450

60
Q

What is hydrolysis?

A

Addition of water to an ester or amide to break the bond and form two smaller molecules.

61
Q

Addition of water to an ester leads to…

A

acid and alcohol

62
Q

Addition of amides leads to…

A

acid and amine

63
Q

What are some pseudocholinesterase catalyzed drugs that undergo hydrolysis?

A

Succinylcholine, cocaine, procaine, chloroprocaine, tetracaine, neostigmine, edrophonium.

64
Q

What are some non-esterase dependent drugs that undergo hydrolysis?

A

remifentanil, atracurium, cisatracurium, esmolol, aspirin, clevidipine, MOC-etomidate.

65
Q

Why are phase II reactions also known as synthetic reactions?

A

The body synthesizes a new compound by donating a functional group.

66
Q

Conjugation always leads to a more _____(polar/non-polar) compound, that is ______(ionized/non-ionized) therefore more easily extractible via glomerular filtration.

A

polar

Ionized

67
Q

During a phase II reaction a conjugate from the phase I reaction joins a _____, ______, or ________ group to form an ester or amide bond.

A

OH, COOH, or NH

68
Q

Why is cytochrome P450 also called mixed-function oxidase system?

A

It includes both oxidation and reduction and has low substrate specificity

69
Q

What is enzyme induction?

A

Stimulation of enzymes over a period of time increases the activity and can more quickly break down agents.

70
Q

What is enzyme inhibition?

A

Exposure to certain drugs and chemicals leads to accumulation of the agent, increases plasma levels, and may lead to toxicity.

71
Q

What is the elimination half-life (t1/2)?

A

The time necessary for the plasma content of a drug to drop half of its prevailing concentration after a rapid bolus injection

72
Q

How many half lives must pass before the drug is considered fully eliminated and termination of action usually occurs?

A

4

73
Q

After 4 half lives what % of drug is eliminated and what % remains in the body?

A

93.75 % is eliminated and 6.25% remains in the body.

74
Q

What is zero-order elimination?

A

A constant amount (not percentage) is eliminated over time.

75
Q

What is the Michaelis-Menton model?

A

Dose dependent and follows zero order at high doses and first order once drug levels have fallen.

76
Q

What is the context-sensitive half-time?

A

The time too halving of the blood concentration after termination of drug administration by an infusion designed to maintain a constant concentration. Does not mean recovery from anesthetic though.

77
Q

What is the equation for clearance?

A

Clearance = Q x E

Q= blood flow
E= extraction ratio
78
Q

Drugs that have an extraction ratio of _____ or greater rely heavily on perfusion of the liver to be cleared.

A

0.7

79
Q

What does perfusion-dependent elimination mean?

A

Hepatic blood flow outweighs enzymatic activity in clearing drugs from the body. A decrease in hepatic blood flow decreases rate of clearance.

80
Q

Drugs with an extraction ratio of _____ rely very little on hepatic perfusion, this is known as _________ elimination.

A

0.3

capacity-dependent

81
Q

What are examples of high hepatic clearance drugs?

A

verapamil, morphine, & lidocaine

82
Q

What are examples of low hepatic clearance drugs?

A

diazepam & theophylline.

83
Q

______(lipid / water) soluble drugs are easily excreted by the kidneys, whereas ________(lipid / water) soluble drugs are reabsorbed by the kidneys into circulation.

A

water

lipid

84
Q

Are weak acids better excreted in alkaline or acidic urine?

A

alkaline

weak bases are better excreted in acidic urine.

Lindsays Flashcardlet (27 decks)

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