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Pharmacology > opioid pharmacology > Flashcards

opioid pharmacology Flashcards

1
Q

what are the naturally occurring opioids?

A

morphine

codeine (weak)

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2
Q

What are the drugs that were made from simple chemical modifications of the naturally occurring opioids?

A

diamorphine
oxycodone
dihydrocodeine

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3
Q

what are the synthetics opioids?

A

pethidine
fentanyl
alfentanil
remifentanil

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4
Q

What is a synthetic partial agonist of the opioids?

A

buprenorhine

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5
Q

Which drug is an antagonist of the opioids?

A

naloxone

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6
Q

What are the routes of administration of the opioids?

A 
subcut
IM
IV
IV (PCA - pt controlled analgesia)
epidural/CSF
transdermal patches for fentanyl
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7
Q

What percentage of oral (enteral) morphine is metabolised in first pass metabolism and what does this mean if giving the drug IV/subcut/IM ie via parenteral routes?

A

50% - half the dose if parenteral route used

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8
Q

How long dose a single dose of morphine last for?

A

3-4 hours

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9
Q

What are MST CONTINUS tablets and how often are they given?

A

slow release preparations of morphine given 12 hourly

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10
Q

What is diamorphine?

A

morphine that has been chemically transformed into diacetylmorphine

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11
Q

How does diamorphine compare to morphine?

A

more potent and faster acting, as crosses the BBB faster (called heroin) - so more addictive

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12
Q

What class are opioids?

A

class A

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13
Q

What drug is given to drug addicts?

A

bupromorphine - partial opioid agonist

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14
Q

Why is it important to titrate the amount of naloxone?

A

Because if all the morphine is blocked suddenly, the pt may wake up in pain, so give small increases in dose at a time

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15
Q

How fast does IV morphine take to work?

A

1 minute

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16
Q

How long does it take for subcut morphine to peak?

A

1 hour

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17
Q

What is the difference between potency and efficacy?

A

potency - how much do you need to give to get the effect

efficacy - how much of it that you give actually does the effect that you want

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18
Q

How do opioids work?

A

descending inhibition of pain - inhibit the release of pain transmitters at the spinal cord and midbrain and modulate perception of pain in higher centre giving euphoria and so changing the emotional perception of pain

19
Q

Which is stronger dihydrocodeine or codeine?

A

dihydrocodeine is more potent

20
Q

Which is stronger oxycodone or morphine?

A

oxycodone

21
Q

Name some opioid receptors

A

MOP, kappa (KOP), delta (DOP) and nocioceptin opioid like receptor (NOP) - the drugs we use at the moment are all MOP

22
Q

What is the current aim for making new opioid drugs?

A

analgesia without the side effects of resp depression and addiction

23
Q

What dictates the potency of a drug?

A

how well the drug binds to the receptor ie affinity

24
Q

What dictates efficacy?

A

whether the drug is a full or partial agonist

25
Q

From most potent to least potent list morphine, pethidine and diamorphine

A

diamorphine
morphine
pethidine

26
Q

For a 70kg male what dose would you give of:
diamorphine
morphine
pethidine

A

diamorphine 5mg
morphine 10mg
pethidine 100mg

27
Q

Which direction does giving naloxone shift the morphine dose response curve?

A

to the right - as you have to give more morphine to get the same effect with naloxone

28
Q

Will you get a maximal response from buprenorphine?

A

no - as it is a partial agonist of the opioid receptor

29
Q

What is tolerance?

A

down regulation of the receptors with prolonged use, so need higher doses to achieve the same effect

30
Q

What is dependence?

A

psychological - craving and euphoria, physical

31
Q

how long does opioid withdrawal last?

A

72 hours

32
Q

what are the side effects of opioids?

A 
resp depression
sedation
nausea and vomiting 
constipation
itching 
immune suppression
endocrine effects
33
Q

Why do we get side effects with opioids?

A

as opioid receptors exist outside the pain system - in the digestive tract, resp control centre

34
Q

why do we need to titrate the dose with opioids?

A

as different people have a different sensitivity to opioids

35
Q

What should you do if a pt has opioid induced resp depression?

A

call for help
ABC
naloxone - IV, titrate to effect
self inflating oxygen bag

36
Q

What is co-codamol?

A

mixture of paracetamol and codeine can still get resp depression and addiction

37
Q

How can we avoid resp depression with opioids?

A

titrate to effect - 1ml diluted in 10ml saline

38
Q

What type of pain should opioids mainly be used for?

A

chronic cancer pain, as there are dangers of addiction and death from using opioids in non-chronic cancer pain

39
Q

What is the significance of pharmacogenetics in codeine?

A

codeine is a prodrug - needs to be metabolised by CYP2D6, the activity of this cytochrome is decreased in 10-15% of the Caucasian population and is absent in 10%, so codeine will have a reduced or absent effect in these people
and in 5% CYP2D6 is overactive, so mire at risk of resp depression

40
Q

How is morphine metabolised?

A

it is metabolised to morphine 6 glucoronide which is more potent than morphine and is renally excreted

41
Q

What can happen if a pt with renal failure is given morphine?

A

morphine will build up and may cause resp depression

42
Q

What should be done in pts with renal failure?

A

reduce the dose and increase timing intervals, can be dangerous to use morphine so can use oxycodone instead

43
Q

What is tramadol?

A

it is a weak opioid agonist that is stronger than codeine

also a prodrug and requires CYP2D6 to become active

44
Q

What can tramadol interact with and why?

A

SSRIs
tricyclic antidepressants
MAOIs
as it is a serotonin and noradrenaline re-uptake inhibitor, so take care when prescribing it to pts on antidepressants

Pharmacology (10 decks)

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