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Pharmacology > Pharmacokinetics III > Flashcards

Pharmacokinetics III Flashcards

1
Q

What is the goal of bio transformation and metabolism of drugs xenobiotics?

A

Promote their elimination from the body

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2
Q

What does the bio transformation of drugs convert lip soluble, non-ionized compounds to?

A

Water soluble, ionized metabolites

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3
Q

If a drugs molecular weight is <350, what organ excretes it?

A

Kidney

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4
Q

If a drugs molecular weight is >350, what is it excreted in?

A

Bile

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5
Q

Where does most metabolism occur?

A

Liver

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6
Q

What is an example of a drug that needs to be metabolized to be active? What is its active metabolite?

A

Codeine

Morphine

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7
Q

What is an example of a metabolite that is more active than the parents drug?

A

Parent drug diazepam is converted to nordiazepam and then to oxazepam

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8
Q

What is an example of a drug that is metabolized to toxic metabolites? What is the toxic metabolite?

A

Acetaminophen

N-acetyl-p-benzo-quinone imine

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9
Q

In acetaminophen metabolism, the increased production of metabolites leads to what?

A

Oxidative stress and hepatotoxicity

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10
Q

Ethanol induces acetaminophen metabolism through what?

A

CYP2E1

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11
Q

What is phase 1 of bio transformation reactions?

A

Convert lip soluble , non-ionized compounds to more ionized, hydrophilic metabolites

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12
Q

What is phase II of biotransformation reaction?

A

It adds an ionized, charged particle to a phase I metabolite to form a more polar and hydrophilic conjugate

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13
Q

What type of phase I reactions are most common?

A

Oxidation

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14
Q

Are phase I reactions compound specific?

A

There are no specific enzymes metabolizing a particular drug
Enzymes instead INTRODUCE or MASK specific functional groups or bonds of multiple drugs

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15
Q

What kind of phase I enzymes are inducible ?

A

Microsomal (CYP450s)

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16
Q

What is the function of CYP450s?

A

Microsomal enzymes in the liver that oxidase drugs, acting as a handle for phase II conjugation

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17
Q

What P450 subtype metabolizes > 50% of drugs

A

3A4

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18
Q

What is the ONLY phase II enzyme that is inducible?

A

Glucuronyl transferase

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19
Q

What induces CYP1A2?

A

Smoking, chargrilled food

20
Q

What induces CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C18, CYP3A4?

A

Barbiturates/phenobarbital, St John Wort

21
Q

What induces CYP2E1?

22
Q

What is an inhibitor of CYP2D6?

A

Fluoxetine (Prozac)

23
Q

What is an inhibitor of CYP3A4?

A

Grapefruit juice

24
Q

Some drug oxidation reactions are catalyzed by other enzymes rather than via CYP450s. For example, ______ is metabolized by a soluble cytoplasmic enzyme, alcohol dehydrogenase, in addition to CYP2El.

25
Q

Non-oxidative reactions such as reductive reactions add a hydrogen atom. What is an example of a drug that works in this way?

A

Warfarin. It is inactivated by conversion by CYP2A6.

26
Q

Non-oxidative reactions such as hydrolytic reactions occur in plasma in many tissues. What is an example of a drug that works in this way?

A

Esterases and amidases (Succinylcholine, local anesthetics)

27
Q

Although rare, there are some drugs that undergo
phase II reactions BEFORE phase I reactions. For
example, _____ is acetylated to acetylhydrazine (phase II)
prior to undergoing hydrolysis (phase I). Acetylation of
drugs often leads to _____.

A

Isoniazid (INH)

hepatotoxicity

28
Q

If a drug molecule has a suitable _____, either in the parent molecule or phase I metabolite, it is susceptible to conjugation

A

functional group

29
Q

The majority of Phase II conjugation reactions occur in the ___ and are mediated by ______.

A

Liver

glucuronidation and UGTs

30
Q

What are the end products of Phase II reactions?

A

Decreased lipid solubility
Polar & inactive
Have a larger molecular weight
Readily eliminated

31
Q

Glucuronidation involves the formation of what phosphate

compound?

A

uridine diphosphate glucuronic acid (UDPGA)

32
Q

What enzyme catalyzes the transfer of glucuronic acid to the substrate forming a bond

A

UDP glucuronyl transferase (UGT)

33
Q

What is a genetic polymorphism?

A

Mutation that can lead to enzyme deficiency and altered response to drugs

34
Q

What does phase I polymorphism of CYP2D6 cause?

A

Leads to poor metabolism of codeine to morphine

35
Q

What does phase I polymorphism of aldehyde dehydrogenase deficiency cause?

A

Alcohol flush reaction

36
Q

In the GI tract, digestive or bacterial enzymes may ___
the conjugated drug which can then be reabsorbed into
the bloodstream

37
Q

Excretion is enhanced by agents that:

A

1) bind drugs in the intestine (charcoal) increasing peristalsis 2) antibiotics that eliminate the GI bacteria (birth control)

38
Q

What is an example of a drug that is excreted very quickly?

A

Penicillin

39
Q

What is an example of a drug that is excreted very slowly?

40
Q

Which of the following enzymes is NOT inducible?

  1. glucuronyl transferase
  2. CYP2E1
  3. N-acetyltransferase
  4. CYP3A4
  5. CYP1A2
A

N-acetyltransferase

41
Q

Enterohepatic circulation:

  1. Increases half-life of a drug
  2. Decreases half-life of a drug
  3. Increases the clearance of a drug
  4. Is not influenced by GI motility
  5. happens only when toxic doses are administered
A

Increases half-life of a drug

42
Q

Which of the major elimination functions will decrease first with advancing age?

  1. G.I elimination
  2. renal elimination
  3. phase I metabolism
  4. conjugations
A

renal elimination

43
Q

First-order elimination is dependent on :

  1. Plasma concentration
  2. Biological system
A

Plasma concentration

44
Q 
Lidocaine – CL = 38.4 L/hr
 F = 0.35; TC = 3mg/L
t1/2 = 2 hrs
t = 2 hrs. 
What is the proper maintenance dose if administered IV?
1. 30mg 
2. 100mg
3. 180mg 
4. 230mg 
5. 300mg
45
Q

What does phase II polymorphism of fast and slow metabolizers cause?

A

Isoniazid (INH) has bi-modal distribution

“slow metabolizers” and “fast metabolizers”

45
Q

Fast and slow acetylators for Isoniazid are examples of what?

A

Phase II polymorphisms

Pharmacology (25 decks)

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