Drug Metabolism Flashcards Preview

Principles of Disease > Drug Metabolism > Flashcards

Flashcards in Drug Metabolism Deck (22):
1

What is the effect of metabolism

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

2

What happens to lipid soluble substances instead of getting excreted?

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

3

Purpose of metabolism?

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

4

What are prodrugs?

Drugs activated following metabolism

5

What are phase 1 reactions of metabolism?

OXIDATION
REDUCTION
HYDROLYSIS

6

What is the purpose of phase 1 metabolism?

Increases polarity of the compound

Provides active site for phase 2 metabolism

7

What is the most important super family of metabolising enzymes?

P-450 enzymes

8

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

Important in oxidative drug metabolism

9

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

CYP3A4 - Liver + Gut

10

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

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

11

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

Enzyme responsible for the metabolism of theophylline is induced by smoking

12

What does phase 2 metabolism involve?

Conjugation

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

Usually results in inactivation

13

What factors affect metabolism?

Other drugs/herbals/natural substances
Genetics
Hepatic blood flow
Liver disease
Age
Sex
Ethnicity
Pregnancy

14

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

Increased synthesis of the enzyme - increased activity - Decreased drug effect

15

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

Reversible or irreversible binding to the enzyme

Metabolism decreased

16

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)

Increased drug toxicity

17

What are the four phenotype subpopulations of metabolizers?

Poor metabolizers (PM)
Intermediate metabolizers (IM)
Extensive metabolizers (EM)
Ultrarapid metabolizers (UM)

18

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

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

19

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

At puberty

20

What areas in drug response does disparity occur between genders?

Absorption
Distribution
Metabolism
Eliminiation

21

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

The trimester she is in

Hormonal changes

22

What factors brought about in old age alter drug metabolism?

Plasma protein
Lean body mass
Liver weight

DECREASE

Other drugs taken to treat chronic illness