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Diagnostics and Therapeutics > Pharmacokinetics: Drug absorption, Distribution, and Elimination > Flashcards

Pharmacokinetics: Drug absorption, Distribution, and Elimination Flashcards

1
Q

Involves absorption of the drug from aqueous solution in the stomach or intestinal lumen across GI epithelial membranes into the plasma

A

The oral route (enteric drug absorption)

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2
Q

What are the two types of drug absorption across GI membranes?

A

Active transport and Passive transport

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3
Q

Drugs bind to a protein carrier in the membrane with a high degree of structural specificity in

A

Active Transport

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4
Q

Transport system is commonly linked to ATP consumption and can thus transport against a concentration gradient

A

Active Transport

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5
Q

The active transport system is readily

-Limits the amount of drug that can be transported

A

Saturated

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6
Q

More common than active transport, since the system is less selective with regard to what drugs can be transported

A

Passive transport

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7
Q

The passive transport system is not readily saturatable because it does not depend on a

A

Protein carrier

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8
Q

In passive transport, drugs will only move

A

Down a concentration gradient

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9
Q

“Water loving” drugs that form hydrogen bonds with aqueous solvents.

❖ Usually possess a net charge that makes it difficult to pass through a lipid membrane

A

Hydrophilic Drugs

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10
Q

The only hydrophilic drugs that can pass through protein pores and be passively transported across biological membranes are those that are

A

Small (MW less than 100)

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11
Q

Have no net charge at physiological pH and can therefore pass through biological membranes more easily than hydrophilic drugs

A

Hydrophobic (Lipophilic) Drugs

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12
Q

Best predictor of drug entry into the body

A

Lipid-To-Water Partition Coefficient (P)

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13
Q

Will pass more readily through the GI epithelial membranes

A

Drug with higher P value

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14
Q

Only uncharged drugs can move passively across

-Why the distinction between weak acids and bases is so important

A

GI membranes

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15
Q

The distribution of unprotonated to protonated drug can be determined from the

A

pKa and ambient pH

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16
Q

A very important predictor of drug absorption when we know the pH at the site of absorption

A

pKa

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17
Q

At equilibrium, the total drug concentration (uncharged + charged) will be higher in the compartment with the greater degree of

A

pH-dependent ionization

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18
Q

Are not absorbed into the plasma from the stomach, but instead must wait until they enter the intestine where the pH is elevated

A

Weak Bases

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19
Q

What is the pH of the intestines?

A

5.3-5.4

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20
Q

The more blood flow at a site, the more efficiently drug absorption occurs at that

A

Site

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21
Q

Present a 500-times greater surface area for absorption than that of the stomach

A

Intestinal Vili

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22
Q

As a result of this large surface area and a high rate of blood flow, is considered to be the most efficient area of drug absorption

A

Intestine

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23
Q

Defined as the fraction (often given as a %) of orally administered drug that gains access to the systemic circulation in a chemically unaltered form

A

Oral Bioavailability (%F)

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24
Q

What are 4 factors that decrease oral bioavailability?

A

First-pass hepatic transformation, hydrophilicity, metabolic and pH instability, and Physical properties of the drug preparation

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25
Q

When a drug is absorbed along the intestine, the portal circulation brings it to the liver before it reaches the systemic circulation. Many drugs are chemically altered (i.e., metabolized) in this hepatic pass, thereby inactivating a significant fraction of the drug

A

First-Pass hepatic metabolism

26
Q

Most important factor unrelated to drug formulation itself

A

First-pass metabolism

27
Q

If a drug is too hydrophilic, it will never gain access to the body and will thus have a low

A

Bioavailability

28
Q

When two drug preparations differ to the point that their bioavailabilities also differ, they are said to be

A

Bioinequivalent

29
Q

Most common in hydrophobic drugs that are poorly water soluble (e.g., steroids)

A

Bioinequivalence

30
Q

Arises when the bioinequivalence of two drug preparations leads to a difference in therapeutic outcome

A

Therapeutic inequivalence

31
Q

The most important determinant of whether bioinequivalence leads to therapeutic inequivalence is the

A

Therapeutic index

32
Q

One major reason for use of the intravenous (IV) route is increased

A

Speed of action (Ex: anti-arrythmics)

33
Q

Trapped in the plasma because their large size precludes entry into other water compartments, like the IF

A

High molecular weight drugs

34
Q

Smaller size permits entry into the IF, but the drugs cannot passively cross cell membranes to enter the ICF

A

Hydrophilic Low Molecular Weight (LMW) Drugs

35
Q

Can enter all three compartments (plasma, IF, and ICF) and thus swim in the biggest pool

A

Hydrophobic LMW Drugs

36
Q

Distribute only in the plasma because the drug-protein complexes cannot enter the IF or ICF

A

Drugs that bind to plasma proteins

37
Q

Most drugs that bind to plasma proteins bind to

A

Albumin

38
Q

Drug molecules that bind to albumin are inert, since only the free form of the drug is

A

Pharmacologically active

39
Q

Bind strongly to albumin

A

Anionic Hydrophobic Drugs

40
Q

Do not bind strongly to albumin

A

Hydrophilic drugs

41
Q

Premised on the fact that:

  1. The body is a single compartment into which drug distributes uniformly.
  2. The drug concentration in that compartment is the same as the plasma concentration
A

Vd

42
Q

A dilution space normalized to body size and also indicative of a drugs tendency to distribute beyond the vascular space into tissues

A

Vd

43
Q

If the Vd is greater than 42L (total body water volume) than the drug must be

A

Tissue bound

44
Q

Body lipid content can impact distribution (e.g., a lipophilic drug will have a higher Vd in an

A

Obese person

45
Q

Drugs are eliminated from the body in which two primary ways?

A
  1. ) Drug metabolism

2. ) Renal elimination

46
Q

For renal elimination, what are the three partitioning events?

A
  1. ) Glomerular filtration
  2. ) Tubular secretion
  3. ) Tubular reabsorption
47
Q

How much filtrate is there from each 600 mL/min of renal plasma flow in a healthy adult?

A

125 mL/min (GFR = 125 mL/min)

48
Q

A non-saturatable process

A

Glomerular filtration

49
Q

In glomerular filtration, only free (non-protein-bound) drug can be filtered, with drug pKa and lipophilicity having

A

No effect

50
Q

Drug moves from the blood to the lumen of the proximal nephron tubule by an active transport mechanism in

A

Tubular secretion

51
Q

Tubular secretion has two separate carrier-mediated systems for

A

Acids and bases

52
Q

Characterized by saturable protein carriers with little specificity for drug structure

A

Tubular secretion

53
Q

What kinds of drugs can be secreted by tubular secretion?

A

Drugs that were free or protein-bound

54
Q

By the time the drug reaches the lumen of the distal nephron tubule, its concentration is

A

Very high

55
Q

The drug then diffuses passively back out of the nephron lumen into the blood. This is called

A

Tubular reabsorption

56
Q

The only drugs that can undergo tubular reabsorption are

A

Free and unionized drugs

57
Q

In other words, pH partitioning occurs during

A

Tubular reabsorption

58
Q

Alkalinizes the urine and increases anionic (acidic) clearance

A

Bicarbonate

59
Q

Acidifies the urine and increases cationic (basic) clearance

A

Ammonium Chloride (NH4Cl)

60
Q

Refers to the volume of some biological fluid (e.g., plasma) from which, over a specified interval of time, all drug present is removed

A

Clearance

61
Q

Clearance mechanisms typically follow

A

First order kinetics

62
Q

The time it takes for the plasma concentration or the amount of drug in the body to be reduced by one-half (50%)

A

Half-life (t 1/2)

Diagnostics and Therapeutics (12 decks)

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