Metabolism

Question 1

Explain liver metabolism

Answer 1

2 distinct phases:
In phase 1 enzymes acton drug, producing a metabolite by one of the following reactions:
- oxidation, an oxygen atom is added to the compound
- Reduction, a hydrogen atom is added
- Hydroylsis, water is added to the compound
Phase 2 in conjugation
- the metabolite is bound to another molecule, making it more water soluble
Some drugs go through one phase and others go through both stages

Question 2

What factors affect metabolism?

Answer 2

Drug interactions
Repeated drug exposure
Liver function
Down regulation of receptors

Question 3

How do drug interactions affect metabolism?

Answer 3

Id drugs metabolised by the same enzymes are administered together extra enzymes are not able to be produced therefore the enzymes that are available will not be able to metabolise both the drugs at the same rate as normally expected. This will delay the metabolism of either on of the drugs or both leading to toxic effects

Question 4

What does repeated drug exsposure cause?

Answer 4

Can lead to the level producing increased enzyme levels meaning that a drug that the animal has been taking over a period of time will be metabolised more rapidly
This is called induced biotransformation

Question 5

What is the importantce of liver function?

Answer 5

Impared or immature function are less able to metabolise drugs so the dose needs to be lowered or different drugs used.

Question 6

Explain half-life

Answer 6

Time taken for the concentration of the drug in the bloodstream to decrease by half by metabolism and elimination and determines when repeat dosing will be required to maintain therapeutic levels.

Question 7

Explain therapeutic index

Answer 7

This is an indicator of drug safety, drugs with a high TI are safest. CAlculated by
TI = dose required to kill 50% of patients

Question 8

What is the affinity of a drug?

Answer 8

Measure of how well a drug binds to a receptor

Question 9

What is the efficacy of a drug?

Answer 9

The term realtes to the ability of the drug to initate a response once bound to a receptor.
Drugs with a high efficacy are more efficeicnet at causing an effect

Question 10

What is a potency drug?

Answer 10

A drug with both high affinity and efficacy

Question 11

What stage of liver metabolism are cats unable to carry out?

Answer 11

Phase 2