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Pharmacology-Au15 > Absorption, Distribution, and Fate of Drugs. Exam 1 > Flashcards

Absorption, Distribution, and Fate of Drugs. Exam 1 Flashcards

1
Q

What are the sites of absorption for oral drugs?

A

Stomach and small intestine

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2
Q

What is the pH of the stomach?

A

1.4

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3
Q

What is the pH of the small intestine?

A

3.0-7.0

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4
Q

How are oral drugs absorbed?

A

drugs enter from the lumen, through endothelial cell membranes, and into the bloodstream

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5
Q

What are the four basic steps of a drugs life in your body?

A

absorption, distribution, metabolism, excretion

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6
Q

_______ molecules can cross down a concentration gradient (passive diffusion) through the membrane.

A

Lipophilic

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7
Q

_______ is the ratio of the compound’s concentration in a known volume of n-octanol to its concentration in a known volume of water after the octanol and water have reached equilibrium

A

Partition Coefficient

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8
Q

The _______ the partition coeffcient, the more likely a drug will be absorbed by passive diffusion. Why?

A

larger

passive diffusion occurs with lipoPHILIC molecules and PC is essentially a ratio comparing concentration in oil to water

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9
Q

_______ molecules are more likely to be absorbed by passive diffusion.

A

Smaller

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10
Q

More _______ moieties will make a compound more soluble in water and ______ likely to cross a membrane by passive diffusion.

A

polar

less

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11
Q

Why is pH important when considering absorption of drugs?

A

pH of drugs that are acidic or basic will dramatically affect the location at which it is absorbed

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12
Q

Aspirin has a pKa of 3.4 and will be absorbed in the ______.

A

Stomach

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13
Q

Codeine has a pKa of 8.1 and will be absorbed in the ______.

A

small intestine

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14
Q

A lower pKa indicates that the drug will be absorbed in a more _______ environment.

A

acidic

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15
Q

A higher (more positive) pKa indicates that the drug is more ______ and will be absorbed in a similar environment such as the _______.

A

basic

small intestine

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16
Q

Facilitated diffusion across a cell membrane utilitzes ________ or carrier proteins.

A

protein channels

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17
Q

What are the three methods of diffusion that are used by drugs?

A

Passive, Facilitated, Active Transport

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18
Q

_____ transporters are active transporters that use ATP to kick drugs out of cells.

A

ABC

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19
Q

____ transporters exchange Na+ for K+ to transport drugs that are organic acids or bases.

A

SLC

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20
Q

What are the two transporter types used to actively transport drugs?

A

ABC and SLC

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21
Q

True or False: SLC Transporters exchange Cl and K to move organic drugs.

A

False: exchange of Na and K

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22
Q

Name five factors that affect oral absorption of drugs.

A
  1. pH
  2. Surface area
  3. Gastric emptying
  4. Dosage Form
  5. Drug inactivation
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23
Q

How does surface area affect oral absorption of drugs?

A 
Greater surface area = more time
Small intestine (6-8 hrs) > stomach (30min-4hrs)
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24
Q

What administration instructions would reflect gastric emptying properties?

A

“take with food”

if a drug needs to pass more quickly, it should be taken on an empty stomach. if a drug needs lipid transport, it should be taken with food

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25
Q

Slow Release Tablet is an example of ________ and the variations exist due to presence or absence of _______.

A

dosage form

surface proteins

26
Q

Other than orally, what are five additional methods for drugs administration?

A
  1. Inhalation (asthma, COPD)
  2. Intravenous
  3. Intramuscular (gaps in endothelium)
  4. Subcutaneous
  5. Topical
27
Q

Greater amount of blood getting to the tissue, known as increased ________, will increase the amount of drug entrance.

A

profussion

28
Q

Lipophilic drugs are fast; whereas, water soluble drugs must pass through _______ and are much slower.

A

endothelial gaps

29
Q

Similar to absorption from the lumen, drugs may enter cells from the ________.

A

interstitial fluid

30
Q

Name a critical location where drug distribution is restricted.

A

CNS-blood brain barrier

31
Q

What is the volume of distribution?

A

an indication of how a drug is distributed, based on how much is in the plasma and how much was added.
Vd = Q/C
Vd = amt. administered/ concentration at equilibrium

32
Q

An average person contains 41 total liters: ____ liters of plasma, ____ liters of interstitial space, and _____ liters of cells.

A

3 plasma
9 space
29 cells

33
Q

If a drug is _____ soluble, you can administer the drug, measure concentration in plasma, and calculate the Vd to get an idea where it is distributing.

A

Water

34
Q

If a drug goes to plasma and interstitial space, but not into cells, the Vd would = ______

A

12 liters

35
Q

If a drug goes only to plasma, the Vd would =______

A

3 liters

36
Q

If a drug goes to cells but not plasma or interstitial space, the Vd would =_______.

A

29 liters

37
Q

If a drug distributes everywhere, such as urea, what would its volume of distribution be?

A

41 liters

38
Q

What are the phases of drug metabolism?

A

phase I: Add/Uncover functional group, make it polar
phase II: Conjugation, link something to it
phase III: processed and pumped out of cells

39
Q

Where does most drug metabolism take place?

A

liver

40
Q

What are microsomes?

A

membrane bound enzymes that metabolize drugs

41
Q

Where do microsomes bind?

A

smooth ER of hepatocytes

42
Q

Phase I reactions can be broadly grouped into what three categories?

A

Oxidations
Reductions
Hydrolysis

43
Q

What is the most important of the phase 1 oxidation systems?

A

P450 enzymes

44
Q

Cytochrome ____ enzymes catalyze the oxidative metabolism of xenobiotics, the initial step in the biotransformation and elimination of a wide variety of drugs and environmental pollutants

A

P450

45
Q

Where are cytochrom P450 enzymes found?

A

smooth ER of liver cells

46
Q

Reductions most commonly occur in _________.

A

enteric bacteria

47
Q

Drug hydrolysis involves splitting of ____ or ____ to yield an acid and an alcohol.

A

esters

amides

48
Q

__________ metabolism occurs in the liver and other tissues when a drug mimics a natural substance.

A

Non-microsomal

49
Q

What are six factors that will affect drug metabolism?

A
  1. Entry to liver
  2. Enzyme inhibition
  3. Enzyme induction
  4. Genetics
  5. Age
  6. Pathology
50
Q

When metabolizing drugs, there are two rates k1 and k2. k1 is the movement to the liver, k2 is the metabolism. Which rate is typically limiting (slower)?

A

k1 (movement to the liver) is typically slow

51
Q

Protein binding will ______ drug metabolism.

A

slow down

52
Q

Transporters will ______ drug metabolism.

A

speed up

53
Q

Where are drugs typically excreted?

A

the kidney

54
Q

What are the three components of the kidney filtration?

A

glomerular filtration
tubular reabsorption
active transport

55
Q

A major area of filtration within the glomeruli occurs at ________.

A

The basement membrane

56
Q

The glomerulus sits within _________.

A

Bowmans Capsule

57
Q

Tubular reabsorption includes passive transport of _____, active transport of _____, and ____ via osmosis.

A

Cl-
Na+
water

58
Q

True or False: Some compounds are actively pushed out from the capillary endothelium into the urine.

A

True

59
Q

What does half-life of a drug measure?

A

the speed at which half of the drug has cleared

60
Q

How many half-lives must occur in order to have only 6% of drug remaining?

A

four

50, 25, 12, 6

61
Q

If you have two drugs and neither is reabsorbed. Drug 1 is filtered, Drug 2 is actively secreted. Which drug will clear faster?

A

Drug 2

62
Q

Aspirin is absorbed in the stomach where pH is low. If pH is increased, what will happen?

A

more aspirin will be ionized and it will be less likely to be absorbed out of the blood or reabsorbed by the kidney

Pharmacology-Au15 (4 decks)

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