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Sem 3: Pharm > Metabolism + Excretion - FORNO > Flashcards

Metabolism + Excretion - FORNO Flashcards

1
Q

________ is everything the drug does to the body

A

Pharmacodynamics

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2
Q

__________ is everything the body does to the drug after administration

A

Pharmacokinetics

  1. Absorption
  2. Distribution
  3. Metabolism
  4. Excretion
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3
Q

What are the main effects of drug biotransformation?

A
  1. Change in physicochemical properties of the drug
  2. Change in pharmacologic activity
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4
Q

What is the most common site of biotransformation?

A

liver

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5
Q

What are examples of biotransformation?

A
  1. Active drug to inactive metabolite
  2. Active drug to active metabolite
  3. Inactive drug to active metabolite
  4. Non toxic drug to toxic metabolite
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6
Q

What is bioinactivation?

A

Conversion of a parent drug to an inactive metabolite

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7
Q

_________ is an enzyme that plays a key role in metabolism of drugs

A

Cytochrome P450

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8
Q

What does it mean that enzymatic reactions are saturable?

A

Increasing the concentration of a drug does NOT affect reaction rate

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9
Q

What occurs if drug A inhibits the enzyme for drug B?

A

Drug B will not be metabolized + remains in the body longer

  • cant be eliminated as quickly
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10
Q

What occurs if Drug A induces the enzyme for Drug B?

A

This induces Drug B to be metabolized and excreted faster

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11
Q

What is the outcome of phase 1 biotransformation?

A

Metabolites can be more or less water soluble + may be inactive, less active, or more active than parent compound

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12
Q

What drugs must go to Phase II biotransformation prior to excretion?

A

Lipophilic drugs

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13
Q

Conjugation is deficient in?

A

Cats and neonates

** deficient in cats bc they lack glucuronyl transferases

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14
Q

What is the goal of a drug that has gone through phase II biotransformation?

A

Drug is usually inactive, water soluble, and non toxic

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15
Q

What enzymes are dogs deficient in?

A

Acetylating enzymes

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16
Q

What enzymes are cats deficient in?

A
  1. Glucuronyl transferases
  2. Salivary amylase

** also deficient in hydroxylation and dealkylation

17
Q

Which route of drug administration has a first-pass effect?

A

Oral meds- given PO

18
Q

________ enzymes are inducible by drugs

A

microsomal

19
Q

Renal excretion is dependent on what factors?

A
  1. GFR
  2. Active tubular secretion
  3. Passive tubular reabsorption

Sum of all 3 = total renal excretion

20
Q

How is total renal excretion measured?

A

By adding

  1. GFR
  2. Active tubular secretion
  3. Passive tubular reabsorption
21
Q

What factors affect glomerular filtration?

A
  1. Blood flow / BP
  2. Molecular size (small moves fastest)
  3. Molecular charge ( + charged molecules can pass and be excreted )
  4. Plasma protein binding (only unbound drugs are freely filtered)
22
Q

How does degree of ionization affect passive tubular reabsorption?

A

The more ionized the drug, the less reabsorption occurs = MORE drug is excreted

23
Q

What type of drugs are excreted quicker by the kidney if pH of urine is low/acidic?

A

Weak basic drugs

24
Q

What type of drugs are excreted quicker by the kidney if pH of urine is high/alkaline?

A

Weak acidic drugs

25
Q

What factors affect passive tubular reabsorption?

A
  1. Physicochemical properties of the drug - water soluble, ionized, polar drugs cant be reabsorbed and are excreted
  2. Degree of ionization - more ionized = less reabsorption
  3. pH of urine
  4. Fluid therapy / diuretics - decreases renal absorption
26
Q

What is the 2nd most important organ for excretion of drugs?

A

Liver

** drug excreted in bile

27
Q

What is enterohepatic circulation?

A

conjugates of lipophilic compounds are excreted into bile, travel to SI where they are converted back into lipid soluble free drugs to be reabsorbed

** prolongs half life of drug

28
Q

What is first order kinetics?

A

rate of removal of a drug from plasma is proportional to the concentration present at a given time

constant % of a drug is eliminated per unit time

29
Q

What is half life?

A

time required for the body to eliminate 1/2 of the drug

30
Q

After how many half lives is a drug almost completely eliminated from plasma?

A

5-6

31
Q

What is total body clearance?

A

Rate of drug elimination from the body, from all routes, relative to the conc. of drug in plasma

32
Q

Increased Vd results in ________ half life, and ________ clearance

A

Increased, decreased

-stays in body longer

33
Q

Increased half life results in _________ clearance

A

Decreased

34
Q

Decreased Vd results in ________ half life

A

Decreased

-eliminated from body faster

35
Q

What if the extraction ratio is 0?

A

No drug is taken out/ eliminated

= decreased clearance of drug

36
Q

What if the extraction ratio is 1?

A

All the drug has been taken out / eliminated

= increased clearance of drug

Sem 3: Pharm (9 decks)

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