Drug Metabolism By The Liver

Question 1

First pass metabolism

Answer 1

Drug metabolised usually liver, before reaching systemic circulation.
resulting in a lower concentration of the active substance when it reaches its site of action or systemic circulation
= reduces bioavailability

Question 2

Role of phase 1

Answer 2

Make drug more water soluble
Can easily be excreted via kidneys

Question 3

Catabolism

Answer 3

What happens when you e digest food and the molecules break down in the body for use as energy

Question 4

Cytochrome p450 cycle allows for?

Answer 4

Recyuing of cytochrome p450 and the generation of an oxidised derivative of the drug

Question 5

Most common isoform the cytochrome p450 family

Answer 5

CYP3A4/5

Question 6

Omeprazale is what type of inhibitor?

Answer 6

Proton pump inhibitor used for treating gastric ulcers, ALS inhibitor of CYP2C19

Question 7

Furanocoumarins

Answer 7

In grapefruit nice = mediators grapefruit juice-drug interaction

Question 8

Phase 2 reaction involve?

Answer 8

Conjugation of a reactive group

Question 9

What happens in glucuronidation?

Answer 9

Phase 2 reaction
UDP glucuronide, attaches to N, O or S atoms
Increases water solubility which facilitates excretion

Question 10

Liver receives oxygenated blood-via?

Answer 10

The hepatic artery from the systemic circulation

Question 11

75% of the blood supply to liver is from?
25% is from?

Answer 11

75% = portal vein
25% = hepatic artery

Question 12

Majority of drugs administered orally are absorbed in?

Answer 12

Small intestine which is entirely drained by the portal vein (so contains nutrients and absorbed drugs)

Question 13

Bioavailability

Answer 13

Fraction of a drug dose that reaches the systemic circulation

Question 14

Concentration- time graph: for bioavailability
Area under the curve represents?

Answer 14

How much of the drug has been absorbed in systemic circulation

Question 15

How to calculate f fromconcentration-time graph?

Answer 15

F= AUC oral/ AUC intravenous

Question 16

Significant first pass metabolism increases or reduces bioavailability?

Answer 16

Reduces
Bigger doses need to be given orally than IV

Question 17

First pass metabolism can be avoided by what route of drug administration?

Answer 17

Buccal, sublingual and rectal (to some extent)

Question 18

Enterohepatic circulation

Answer 18

recirculation of bile salts, drugs and their metabolites via biliary excretion and reabsorption in the intestine that can maintain drug plasma concentration

Question 19

Bill is released in small intestine to?

Answer 19

Aid lipid digestion, and can also be used as a means to eliminate waste products

Question 20

Enterohepatic recycling

Answer 20

Process by which biliary excreted drug is reabsorbed in the intestine instead of being removed from the body
May delay elimination

Question 21

Features of enterohepatic recycling

Answer 21

May increase half-life
The therapeutic or toxic effects may be prolonged

Question 22

Kinetics is

Answer 22

The rate of the reaction

Question 23

Enzyme kinetics for first order

Answer 23

Doubling concentration of the drug doubles the reaction rate

Question 24

Enzyme kinetics for zero order

Answer 24

Reaction rate is always the same irrespective of drag concentration
Plateau line

Question 25

Enzyme kinetics for non-linear

Answer 25

Reaction rate increases with drug concentration until enzymessaturated and rate reaches constant

Question 26

For zero order on enzyme kinetics drug elimination half life (graph) is

Answer 26

Constant, so drug is eliminated per unit time

Question 27

For first order on enzyme kinetics drug elimination half life (graph) is

Answer 27

Constant proportion of drug iseliminated per unit time Graph curves down

Question 28

Enzyme induction has what effects on enzyme activity and substrate drugs?

Answer 28

Increased enzyme activity and metabolism of substrate drugs = lower plasma concentrations and less efficacy/toxicity

Question 29

Enzyme inhibition has what effects on enzyme activity and substrate drugs?

Answer 29

Decreased enzyme activity and metabolism of substrate drugs = higher plasma concentrations and more efficacy/toxicity

Question 30

What is warfarin?

Answer 30

Anticoagulant

Question 31

Higher prothrombin time means?

Answer 31

Longer it takes for blood to clot

Question 32

Enzyme inhibition on prothrombin time

Answer 32

Prothrombin time stays higher for longer, patient is more likely to bled

Question 33

Some factor affecting drug metabolising enzymes

Answer 33

Age, smoking, alcohol, food, drugs, liver and kidney disease, genetics, pregnancy

Question 34

Define Therapeutic range

Answer 34

Dosage range or plasma concentration usually expected to achieve the desired tuerapectie effect

Question 35

What is TD 50?

Answer 35

Dose at which you see 50% toxicity

Question 36

What is ED 50?

Answer 36

Dose at which you see 50% effectiveness

Question 37

Theophylline is used for?

Answer 37

Severe forms of COPD

Question 38

Digoxin used in?

Answer 38

Cardiac arrhythmias

Question 39

Lithium is used in?

Answer 39

Bipolar disorder and good disorders

Question 40

Aminoglycosides are?

Answer 40

Antibiotics

Question 41

Cyclosporin prevents?

Answer 41

The body from rejecting transplanted organs