2.2 Pharmacodynamics Flashcards

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1
Q

How do most drugs work?

A

By interacting with endogenous proteins

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2
Q

Name some places where drugs work

A

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

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3
Q

What shapes are michaelis menten curve?

A

Rectangular hyperbola

Drug response proportional to drug concentration

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4
Q

Describe drug selectivity

A

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

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5
Q

Describe drug specificity

A

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

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6
Q

What does affinity define?

A

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

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7
Q

Define efficacy

A

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

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8
Q

What does efficacy describe?

A

The maximum effect of a drug

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9
Q

Describe potency

A

Dose required to produce the desired biological response

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

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10
Q

What is the equation for therapeutic index?

A

Therapeutic index = EC50 adverse effect / EC50 desired effect

Therapeutic index = toxic dose / effective dose

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11
Q

What is the therapeutic window?

A

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

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12
Q

What is the therapeutic window between?

A

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

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13
Q

Give some examples of drugs with a narrow therapeutic window

A

Warfarin, aminophylline, gigoxin and aminoglycoside antibiotics

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14
Q

What do fatty meals do to gastric transit time?

A

Slow it down

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15
Q

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

A

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

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16
Q

What is the problem with taking iron and tetracycline?

A

Bind together to form a chelate

Drug isn’t absorbed

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17
Q

How can absorption be altered?

A

Altered p-glycoprotein activity

18
Q

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

A

Women have more water

Men have more water so concentration of alcohol lower in men

19
Q

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

A

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

20
Q

What can effect metabolism in gut wall/portal system?

A

Changes in blood flow

21
Q

What is the timescale for inhibition if CYP450?

A

Quick onset

Several hours to days

22
Q

What is CYP450 inhibition related to?

A

Half life and clearance of affected drug

Plasma concentration at time of interaction

23
Q

In which phase does enzyme induction occur?

A

Phase 1

24
Q

How long does enzyme induction take to happen?

A

Days to weeks

25
Q

Name two drugs that can act together to cause enzyme induction

A

Carbamazepine and warfarin

26
Q

Name some drugs that are CYP450 inducers

A

Phenytoin
Carbamazepine
Barbiturates
Rifampicin

27
Q

Name some drugs that are CYP450 inhibitors

A
Omperazole 
Disulfiram
Erythromycin 
Valproate 
Isoniazid
28
Q

What may drugs prolonging QT interval cause?

A

Torsade des pointes

29
Q

When is drug disease interaction more common?

A

Extremes of age

Chronic medical conditions

30
Q

Name some renally excreted Drugs

A

Digoxin, aminoglycoside antibiotics

31
Q

What effect will hepatic Disease have on drug half life?

A

Will be longer

32
Q

What impact can falling cardiac output have on drugs?

A

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

33
Q

What effect can grapefruit juice have on CYP450?

A

Inhibits many isoenzymes

Decreasing clearance of drugs like simvastatin, amiodarone, terfenadine

34
Q

What effect can cranberry juice have on drug food interaction?

A

Inhibits some CYP

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

35
Q

What is an adverse drug reaction?

A

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

36
Q

What is a major ADR?

A

Permanent or life threatening

37
Q

What is a moderate ADR?

A

Requiring additional treatment

38
Q

What can increase the risk of ADR?

A

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

39
Q

What biological causes can cause variable drug response?

A
Body weight and size
Age and sex
Genetics
Condition of health 
Placebo effect
40
Q

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

A

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