Metabolism

Question 1

What is main organ of metabolism?

Answer 1

Liver

Question 2

What factors effect metabolism? (8)

Answer 2

1. Genetics cytochrome P450
2. Age
3. Gender
4. Liver size and function
5. Circadian rhythms
6. Body temperature
7. Nutritional state
8. Environmental Factors

Question 3

What is phase 1 pathway of drug metabolism in liver?

Answer 3

Metabolic reactions catalysed by cytochrome p450 enzymes
- many different ones each specific to different drugs
- most common is oxidation
- causes toxic metabolites

Question 4

What is phase 11 metabolism

Answer 4

Conjugation of drug or it’s phase 1 metabolite with an endogenous substance to produce more soluble molecules easy to excrete by kidneys

Question 5

What is phase 111 metabolism in liver

Answer 5

Active drug transport across cell membrane rather than enzyme catalysed reactions

Question 6

What is an inhibitor?

Answer 6

Prolongs action of drug
Eg cimetidine, grapefruit juice

Question 7

What is an inducer?

Answer 7

Shortens action of drug

Question 8

Which type of drugs have most hepatic clearance

Answer 8

Lipid sol drug ( unionised)
Cross cell membranes which are lipid in nature

Question 9

Which type of drug has most renal clearance

Answer 9

Water sol (ionised)

Question 10

What bond does a Reversible inhibitor form?

Answer 10

Non covalent

Eg inhibition of cholinesterase enzyme by physostigmine

Question 11

What bond does a irreversible inhibitor form?

Answer 11

Covelent

Needs new enzymes to be formed for activity to be restored

Eg inhibition of cholinesterase enzyme by organophosphate