Drug Therapy : Drug Metabolism Flashcards

1
Q

What is the effect of metabolism

A

limits the life of a substance in the body, by rendering lipid soluble and non-polar compounds to water soluble and polar compounds so that they can be excreted

Production of toxic metabolites (direct toxicity, carcinogenesis)

Loss of pharmalogical activity Increase in prodrug

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What happens to lipid soluble substances instead of getting excreted?

A

Passively reabsorbed from renal or extra renal excretory sites back into the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Purpose of metabolism?

A

To increase water solubility and so aid excretion or to deactivate compounds (may involve a number of steps).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are prodrugs?

A

Drugs activated following metabolism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are phase 1 reactions of metabolism?

A

OXIDATION

REDUCTION

HYDROLYSIS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the purpose of phase 1 metabolism?

A

Increases polarity of the compound

Provides active site for phase 2 metabolism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the most important super family of metabolising enzymes?

A

P-450 enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the main role of the CYP1-3 families (contained within the P-450 family)

A

Important in oxidative drug metabolism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Where are enzymes found that are responsible for the breakdown of SOME drugs

A

CYP3A4 - Liver + Gut

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why may 5-10% of the population may be immune to the analgesic actions of codeine?

A

Reduced expression of the enzyme responsible for conversion of codeine to morphine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Why do smokers require a higher dose of theophylline than non-smokers?

A

Enzyme responsible for the metabolism of theophylline is induced by smoking

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does phase 2 metabolism involve?

A

Conjugation

Attachment of glucoronic acid, glutathione, sulphate or acetate to the metabolite generated by phase 1 metabolism

Usually results in inactivation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What factors affect metabolism?

A

Other drugs/herbals/natural substances

Genetics

Hepatic blood flow

Liver disease

Age

Sex

Ethnicity

Pregnancy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the effect of induction of drug metabolising enzyme on metabolism?

A
  • Increased synthesis of the enzyme
  • increased activity
  • Decreased drug effect
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the effect of inhibition of drug metabolising enzyme on metabolism?

A

Reversible or irreversible binding to the enzyme

Metabolism decreased

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the effect of decreased enzyme activity or lack of an enzyme responsible for drug metabolism?(can be as a result of genetic polymorphism)

A

Increased drug toxicity

17
Q

What are the four phenotype subpopulations of metabolizers?

A
  1. Poor metabolizers (PM)
  2. Intermediate metabolizers (IM)
  3. Extensive metabolizers (EM)
  4. Ultrarapid metabolizers (UM)
18
Q

Describe the prevalence of drug metabolising enzymes in the fetus or premature infant?

A

Deficient or reduced, renal function is also deficient so drug and metabolites rapidly build up to toxic levels.

19
Q

Who metabolises drugs faster - a teenager at puberty or an adult?

A

At puberty

20
Q

What areas in drug response does disparity occur between genders?

A

Absorption

Distribution

Metabolism

Eliminiation

21
Q

What can affect the metabolism of drugs in a pregnant woman?

A

The trimester she is in

Hormonal changes

22
Q

What factors brought about in old age alter drug metabolism?

A

Plasma protein

Lean body mass

Liver weight

DECREASE

Other drugs taken to treat chronic illness