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Pharmacology > Metabolism Of Drugs > Flashcards

Metabolism Of Drugs Flashcards

1
Q

What are the 3 types of metabolism of drugs?

A

1) drug metabolism as a mechanism of termination of drug action
2) drug metabolism as a mechanism of drug activation
3) drug elimination without metabolism

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2
Q

How does drug metabolism as a mechanism of termination of drug action work?

A

Action of drug is terminated before excreted b/c they are metabolized to biologically inactive derivatives, resulting in more polar, less lipid-soluble drugs, making for less renal reabsorption and more drug excreted

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3
Q

How does drug metabolism as a mechanism of drug activation work?

A
  • Some drugs are inactive as they are administered (prodrugs), having to be metabolized in the body to become active
  • Many drugs are active as administered and have active metabolites as well
  • other drugs have toxic metabolites
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4
Q

How does drug elimination without metabolism work?

A

Some drugs such as lithium are not modified by the body, and continue to act until they are excreted

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5
Q

How is phase 1 of metabolism accomplished?

A

By enzymes (cytochrome P450) found in smooth endoplasmic reticulum; these enzymes make slight modification to the drug to make it more water-soluble, making it easier to get rid of

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6
Q

What type of reactions do phase 2 types of metabolism involve?

A

Conjugation reactions, where an endogenous substrate is conjugated to the drug via the actions of a transferase enzyme (attach another substance with similar high molecular weight = transferase enzyme)

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7
Q

In phase 2 types of metabolism, what is the relative size of the drug-conjugate in order to facilitate elimination?

A

The drug-conjugate has increased size

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8
Q

Who is the phase 2 metabolism system lacking in?

A

Neonates (little kids and babies)

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9
Q

The phase 2 type of metabolism is lacking in neonates, which makes them susceptible to what?

A

To drugs metabolized in this manner

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10
Q

What is the most important organ for drug metabolism?

A

Liver

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11
Q

Metabolism occurs via enzymes located in or on what?

A
  • Smooth endoplasmic reticulum = SER (Phase 1 reactions)
  • Cytoplasm (Phase 2 reactions)
  • mitochondria, cell membrane
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12
Q

What phase reaction occurs in the smooth ER?

A

Phase 1 reactions

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13
Q

What phase reaction occurs in the cytoplasm?

A

Phase 2 reactions

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14
Q

Starting with the endoplasmic reticulum, explain how you see heme

A

ER –> oxidoreductase-CYP complex (enzymes) –> CYP-oxidoreducatase complex (heme complex) –> iron-protoporphryrin IX (Heme)

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15
Q

What enzymes are named with the root CYP?

A

Cytochrome p450 enzymes

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16
Q

Cytochrome p450 enzymes are named with a root ____ followed by a number designating the family, letter denoting the subfamily, and another number designating the form.

A

CYP (“sip”)

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17
Q

What is the family, subfamily, and gene number for CYP3A4?

A

Family = 3
Subfamily = A
Gene number = 4

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18
Q

How many CYPs are there that metabolize drugs in humans?

A

12

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19
Q

What are the most active CYPs for drug metabolism?

A

CYP2C
CYP2D
CYP3A (which CYP3A4/5 metabolizes about 50% of all drugs)

20
Q

Which phase of metabolism reactions involves oxidation, reduction, and hydrolysis?

A

Phase 1 reactions

21
Q

Phase 1 reactions utilize what type of oxidation?

A

Cytochrome P450-dependent oxidation

22
Q

Drugs which increase the expression of p450 enzymes (induce liver to make more enzymes)

A

CYP Inducers

23
Q

Drugs which will reduce the plasma level and therefore the effectiveness of the substrate drug (assuming metabolism inactivates the substrate)

A

CYP inducers

24
Q

What does reducing the effectiveness of the substrate drug do for the drug?

A

It reduces the drug, metabolizing more of them

25
Q

Examples of CYP Inducers:

A

-Benzopyrenes (induce liver to make more enzymes) in cigarette smoke
-Chronic ethanol
-Barbiturates
-Carbamazepine (seizure drug)
-Rifampin (antibiotic used for Tuberculosis)
“Smoking and drinking in Barb’s Car Rif’s her Fin”

26
Q

Example:
In a patient taking oral contraceptives who is later prescribe rifampin for a bacterial infection, predict what happens next:

A
  • induce more liver enzymes –> decreases BC drug’s effectiveness –> PREGGO!!!
  • instead, use different antibiotic or use other contraceptives
27
Q

Drugs which decrease the expression of p450 enzymes

A

CYP Inhibitors

28
Q

Drugs which will increase the plasma level, and therefore increase the toxicity risk of the substrate drug (assuming metabolism inactivates the substrate)

A

CYP Inhibitors

29
Q

When does watching taking CYP inhibitors matter most?

A

When the other drug you’re taking has a really low therapeutic index

30
Q

Examples of CYP inhibitors:

A
  • Cimetidine
  • Erythromycin (popular antibiotic)
  • Grapefruit juice (NOT GRAPE JUICE!!!!)
31
Q

Example:
In a patient taking warfarin as an anticoagulant who is later prescribed cimetidine for peptic ulcers, predict what happens next:

A

Pt is more susceptible for bleeding out (blood in urine and bruising easily)

32
Q

For CYP inhibitors and CYP inducers, can one exposure change the enzymes too much?

A

Not really; you have to have regular exposure to change the enzymes

33
Q

What are the 3 main phase 2 reactions of metabolism?

A

1) glucoronidation
2) sulfation
3) acetylation

34
Q

What enzyme is associated with the phase 2 reaction of glucuronidation?

A

Glucuronosyl transferase

35
Q

Why do neonates have problems with phase 2 reactions?

A

They have reduced glucuronosyl transferase activity, not allowing them to add glucuronosyl transferase to the drug

36
Q

What enzyme is associated with the phase 2 reaction of sulfation?

A

Sulfotransferase

37
Q

What’s an example of an addition of a sulfate group to the drug in a sulfation phase 2 reaction?

A

Minoxidil

38
Q

What enzyme is associated with the phase 2 reaction of acetylation?

A

Acetyltransferase

39
Q

Acetylation has genotype count variation. What does this mean?

A

Slow or fast acetylators
(Slow = don’t have a lot of enzymes = long 1/2 life = slow metabolism
–> can cause drug-induced lupus)

40
Q

What can cause drug-induced lupus?

A

Too much administration of the slow acetylator in the phase 2 reaction, acetylation

41
Q

What do all of the examples of acetyl drugs for phase 2 reactions cause?

A

SLE

42
Q

When you administer UDP-glucuronosyl transferase to salicylic acid, which is UDP-glucuronic acid +, what happens to the size of the drug?

A

It pretty much doubles in size because you’re adding more +UDP, allowing you to more readily get rid of the drug

43
Q

The first step in aspirin metabolism is in what phase?

A

Phase 1

44
Q

The second step in aspirin metabolism is in what phase?

A

Phase 2

45
Q

What phases are being used when aspirin goes through hydrolysis and then oxidation?

A 
Phase 1 (hydrolysis)
Phase 1 (oxidation)
46
Q

What phases are being used when aspirin goes through hydrolysis and then glucuronide (salicyl acyl)?

A 
Phase 1 (hydrolysis)
Phase 2 (glucuronide = salicyl acyl)
47
Q

What phases are being used when aspirin goes through hydrolysis and then glycine (salicyluric acid)?

A 
Phase 1 (hydrolysis)
Phase 2 (glycine = salicyluric acid)

Pharmacology (8 decks)

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