2.2 Pharmacodynamics

Question 1

How do most drugs work?

Answer 1

By interacting with endogenous proteins

Question 2

Name some places where drugs work

Answer 2

Cell surface receptors, nuclear receptors, enzyme inhibitors, ion channel blockers, Transport inhibitors

Question 3

What shapes are michaelis menten curve?

Answer 3

Rectangular hyperbola

Drug response proportional to drug concentration

Question 4

Describe drug selectivity

Answer 4

The more the selective a drug is for its
target, the less chance that it will interact
with different targets and have less
undesirable side effects

Question 5

Describe drug specificity

Answer 5

Targeting drugs against specific receptor
subtypes often allows drugs to be targeted
against specific organ

Question 6

What does affinity define?

Answer 6

The tendency of a drug to bind to a specific receptor type

Question 7

Define efficacy

Answer 7

Ability of a drug to produce a response as a result of the receptors being occupied

Question 8

What does efficacy describe?

Answer 8

The maximum effect of a drug

Question 9

Describe potency

Answer 9

Dose required to produce the desired biological response

Describes the difference doses of two drugs required to exact the same effect

Question 10

What is the equation for therapeutic index?

Answer 10

Therapeutic index = EC50 adverse effect / EC50 desired effect

Therapeutic index = toxic dose / effective dose

Question 11

What is the therapeutic window?

Answer 11

The range of doses that can effectively treat a condition while still remaining safe

Question 12

What is the therapeutic window between?

Answer 12

The lowest dose that has a positive effect and the highest dose before the negative effects outweighs the positive effects

Question 13

Give some examples of drugs with a narrow therapeutic window

Answer 13

Warfarin, aminophylline, gigoxin and aminoglycoside antibiotics

Question 14

What do fatty meals do to gastric transit time?

Answer 14

Slow it down

Question 15

What is the principle behind drinking alcohol following a fatty meal?

Answer 15

Gpfatty meals slow down gastric transmpit time
Alcohol takes longer to get through stomach
Most alcohol absorbed in duodenum so prolong time to get there giving a constant drip effect

Question 16

What is the problem with taking iron and tetracycline?

Answer 16

Bind together to form a chelate

Drug isn’t absorbed

Question 17

How can absorption be altered?

Answer 17

Altered p-glycoprotein activity

Question 18

Why may women and men have different alcohol concentrations when drinking the same amount?

Answer 18

Women have more water

Men have more water so concentration of alcohol lower in men

Question 19

In which situations is it important to thinkabout protein binding interactions?

Answer 19

Drugs given IV
short half life (rapidly cleared)
Narrow therapeutic index
Eg phenytoin

Question 20

What can effect metabolism in gut wall/portal system?

Answer 20

Changes in blood flow

Question 21

What is the timescale for inhibition if CYP450?

Answer 21

Quick onset

Several hours to days

Question 22

What is CYP450 inhibition related to?

Answer 22

Half life and clearance of affected drug

Plasma concentration at time of interaction

Question 23

In which phase does enzyme induction occur?

Answer 23

Phase 1

Question 24

How long does enzyme induction take to happen?

Answer 24

Days to weeks

Question 25

Name two drugs that can act together to cause enzyme induction

Answer 25

Carbamazepine and warfarin

Question 26

Name some drugs that are CYP450 inducers

Answer 26

Phenytoin
Carbamazepine
Barbiturates
Rifampicin

Question 27

Name some drugs that are CYP450 inhibitors

Answer 27

Omperazole 
Disulfiram
Erythromycin 
Valproate 
Isoniazid

Question 28

What may drugs prolonging QT interval cause?

Answer 28

Torsade des pointes

Question 29

When is drug disease interaction more common?

Answer 29

Extremes of age

Chronic medical conditions

Question 30

Name some renally excreted Drugs

Answer 30

Digoxin, aminoglycoside antibiotics

Question 31

What effect will hepatic Disease have on drug half life?

Answer 31

Will be longer

Question 32

What impact can falling cardiac output have on drugs?

Answer 32

Excessive response to hypotension agents
Reduced organ perfusion
So reduced hepatic and renal blood flow and clearance

Question 33

What effect can grapefruit juice have on CYP450?

Answer 33

Inhibits many isoenzymes

Decreasing clearance of drugs like simvastatin, amiodarone, terfenadine

Question 34

What effect can cranberry juice have on drug food interaction?

Answer 34

Inhibits some CYP

Decreased clearance of warfarin, enhanced anticoagulant effect and increased risk of haemorrhage

Question 35

What is an adverse drug reaction?

Answer 35

An unwanted or harmful reaction which occurs after administration of a drug or drugs and is suspected or known to be due to the drug

Question 36

What is a major ADR?

Answer 36

Permanent or life threatening

Question 37

What is a moderate ADR?

Answer 37

Requiring additional treatment

Question 38

What can increase the risk of ADR?

Answer 38

Inappropriate prescribing
Polypharmacy
Extremes of age- altered PK and co morbidity
Narrow therapeutic index
Drugs used near minimum effective concentration

Question 39

What biological causes can cause variable drug response?

Answer 39

Body weight and size
Age and sex
Genetics
Condition of health 
Placebo effect

Question 40

What are some causes of variability in drug response related to conditions of administration?

Answer 40

Dose, formulation ROA
Repeated administration may lead to resistance, tolerance, allergy
Drug interaction