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Flashcards in pharmacokinetics -drug metabolism Deck (24)
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1

drug metabolism

biochemical modification of pharmaceutical substances by living organisms usually through specialized enzymatic activity.

2

what does metabolism do to lipid soluble and
non-polar drugs?

converts them into water soluble and polar substances which are able to be excreted

3

what are prodrugs?

drugs that are activated by metabolism

4

what is the purpose of metabolism?

-increase water solubility and so aid excretion.
-deactivates compounds

5

examples of prodrugs

codeine, enalapril, simvastatin, sacubitril

6

effects of metabolism in a drug

-Loss of pharmacological activity.
-Increase in activity, more active metabolites (prodrugs)
-Production of toxic metabolites

7

what are the effects of toxic metabolites of a drug

-direct toxicity
-carcinogenesis
-teratogenesis (production of congenital abnormalities in an embryo or fetus)

8

phase 1 of drug metabolism

drug is either activated or inactivated by oxidation, reduction or hydrolysis

9

what does phase 1 do to the polarity of an organism?

increases it

10

what is the most important enzyme family for phase 1 metabolism?

cytochrome P-450

11

CYP3A4

the major constitutive enzyme in the liver, also found in the gut so responsible for pre-systemic metabolism

12

CYP2C6

resposible for the metabolism of some antidepressants and codeine to morphine

13

CYP1A2

induced by smoking and is important in the metabolism of theophylline

14

phase 2 of metabolism

involves conjugation, this increases water solubility which enhances excretion of metabolised compound.

15

factors which affect metabolism

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

16

what is induction of drug metabolising enzymes?

increased synthesis and therefore increased activity of an enzyme

17

what effect does enzyme induction have on drug effect?

decreases it as there is increased metabolism

18

examples of enzyme inducers

-alcohol
-smoking
-other drugs
-herbal drugs

19

what are drug enzyme inhibitors?

reduce the activity of drug metabolising enzymes

20

examples of drug enzyme inhibitors

grapefruit juice
clarithromycin
cimetidine
ketoconazole
calcium channel blockers

21

how can genetic variation affect drug metabolism?

-individuals may express different forms of a drug metabolising enzyme
-may also have abnormal levels of an enzyme. too high- reduced effect
too low- drug toxicity

22

what will lack or decreased activity of an enzyme result in ?

increased toxicity

23

how does drug metabolism differ in children?

-often deficient of metabolising enzymes in fetus and premature infant renal function is reduced so drugs can build up.
-by two children can metabolise many drugs more rapidly than adults

24

how does drug metabolism differ in the elderly?

plasma protein, lean body mass and liver weight can be significantly decreased