T2 - Drug Elimination E2 Flashcards

1
Q

What is drug excretion?

A

The process by which intact drugs and its metabolites are irreversibly removed from the body

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2
Q

What is the principle organ for excretion?

A

Kidneys

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3
Q

What are other organs used for excretion besides the kidneys?

A
  1. Lungs
  2. Biliary system
  3. Salivary
  4. Sweat glands
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4
Q

What is a nephron?

A

The functional unit of the kidney involved in excretion

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5
Q

What are the components of the nephron?

A

Vascular and tubular

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6
Q

What are glomerulus?

A

A network of glomerular capillaries

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7
Q

What is the filter of the glomerulus?

A

Bowman’s capsule

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8
Q

What happens when blood enters the glomerulus?

A

Blood is filtered so that free filtrate can pass through the tubule

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9
Q

What are the mechanisms of renal excretion?

A
  1. Glomerular filtration
  2. Tubular secretion
  3. Tubular reabsorption
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10
Q

What mechanisms remove drugs from circulation?

A
  1. Glomerular filtration
  2. Tubular secretion
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11
Q

What mechanisms moves drug from inner tube back into circulation?

A

Tubular reabsorption

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12
Q

What drives glomerular filtration?

A

Passive diffusion

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13
Q

What is the size of molecules that undergo glomerular filtration?

A

MW < 6kDa

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14
Q

What is type of drugs undergo glomerular filtration?

A

Molecules that are unbound to plasma proteins

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15
Q

How is glomerular filtration rate determined?

A

Insulin and creatinine

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16
Q

Why is insulin and creatine used to determine GFR?

A

They undergo filtration without tubular secretion and reabsorption and are not bound to plasma proteins

17
Q

What is the GFR of a healthy individual?

A

110 - 130 mL/min (180 L/day)

18
Q

What kind of process is tubular secretion?

A

Active

19
Q

What are secretion transporters of the PCT and what are do they secrete?

A
  1. OATP secrete organic anions (acids)
  2. OCT secrete organic cations (bases)
20
Q

What happens is probenecid is taken with penicillin?

A

Causes a drug-drug interaction where competitive inhibition that inhibits the secretion of penicillin because both drug are secreted from the same transporter

21
Q

What drives tubular reabsorption?

A

A large concentration gradient across the tubule and plasma is a driving force for passive reabsorption of solutes back into circulation

22
Q

How are small MW drugs reabsorbed?

A

Reabsorption can take place if drug is sufficiently lipophilic and remains un-ionized

23
Q

How are weak acidic and basic drugs effected by tubular reabsorption?

A

The pH of the glomerular fitrate influences their ionization

24
Q

How are large MW, polarized, or ionized molecules reabsorbed?

A

There are not reabsorbed

25
Q

Where do drug molecules go when they escape reabsorption?

A

They will exit the body through urine

26
Q

What are the factors that influence drug excretion?

A
  1. Phyico-chemical properties
  2. Plasma drug concentration
  3. Plasma protein binding of the drug
  4. Miscellaneous factors such as age, disease, and DDI
27
Q

What are the ways drug elimination can be quantified?

A
  1. Half-life
  2. Clearance
28
Q

What is half-life?

A

The time required for 50% of the drug to be eliminated from the body

29
Q

How is the t1/2 of drugs affected by elimination in the first-order?

A

T1/2 is independent of dose and concentration

30
Q

What is the most useful parameter to quantify drug elimination?

A

Clearance

31
Q

Why is clearance referred over t1/2 of quantifying drug elimination?

A
  1. t1/2 is a function of clearance and volume of distribution
  2. Half-life fails to provide insight to drug elimination and can’t predict the impact of disease or drug interactions on drug elimination
32
Q

What does ClH quantify?

A

Drug elimination by hepatic metabolism

33
Q

What does ClR quantify?

A

Unchanged (not-metabolized) drug elimination by renal excretion

34
Q

What are the components of total clearance in the body?

A

ClH + ClR