Opioid Pharmacology Flashcards Preview

Year 2 > Opioid Pharmacology > Flashcards

Flashcards in Opioid Pharmacology Deck (57)
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1
Q

How is 50% of oral morphine metabolised

A

First pass metabolism in the liver

2
Q

What does 50% metabolism of morphine mean for prescription

A

We have to double the dose (10mg morphine = 5mg really)

3
Q

How long does a single dose of morphine last

A

3-4 hours

4
Q

How often is morphine given for ‘slow release’ palliative care

A

Twice a day

5
Q

Benefits of diamorphine vs morphone

A

Diamorphine is more potent and passes across blood-brain barrier more quickly

6
Q

What class are opioids categorised as

A

Class A drugs

7
Q

Why are opioids difficult to get a hold of

A
  1. Secure storage

2. CD (controlled drug) books need two signatures

8
Q

Dihydrocodeine vs codeine

A

1.5 x more powerful

9
Q

How do opioids work physiologically

A
  1. Inhibits release of pain transmitters at spinal cord and midbrain by binding to G-coupled receptors
  2. Modulate pain perception at higher centres and emotional response
10
Q

What two hormones do opioids inhibit to bring bout decreased pain perception

A

Natural endorphins

Enkephalins

11
Q

How do Opioids work

A

Descending inhibition of pain

12
Q

Do opioids bring about sustained activation

A

No

13
Q

What is the problem of sustained activation due to opioids

A

Leads to tolerance and addiction

14
Q

Name of the four receptors

A

MOP
KOP
DOP
NOP

15
Q

What do Kappa morphine receptors do which is different to the other three

A

Causes depression instead of euphoria

16
Q

What receptor do all drugs currently act on

A

M(u) receptors

17
Q

Define Potency

A

How well the drug binds to the receptor

18
Q

Define efficacy

A

How well receptor is activated

19
Q

Which is more potent, Morphine or Diamorphine

A

Morphine (10mg) vs Diamorphine (5mg for same effect)

20
Q

Why does Tolerance occur

A

Down-regulation of receptors with prolonged use

Need higher doses to reach same effect

21
Q

Define dependance

A

Psychological response to tolerance - craving

22
Q

When does opioid withdrawal take place

A

24 hours and lasts 72 hours

23
Q

Where else can opioid receptors be found other than the pain system

A
  1. Digestive tract

2. Respiratory control centre

24
Q

Side effects of opioids

A
  1. Sedation
  2. Nausea
  3. Constipation
  4. Itching
  5. Immune Suppression
  6. Endocrine Effects
25
Q

Why do we start with a small dose of opioids and titrate up

A

Because different patients have a range of sensitivity to opioids

26
Q

How do we treat Opioid induced respiratory depression

A

ABC

Naxolone IV via titration (remember patient sensitivity)

27
Q

What do we have to be aware of when giving Naxolone to drug addicts in A&E

A

Short half-life of naxolone

28
Q

Ho do we titrate Naxolone

A

Dilute 1ml in 10 ml of saline

29
Q

What is the issue with opioid use in Chronic non-cancer pain

A

They are losing effectiveness quickly

More deaths than US traffic accidents and firearms

30
Q

What is the results of opioid addiction on patient

A

Easy to start and difficult to get them off it

31
Q

What kind of drug is codeine

A

Prodrug

32
Q

What enzyme metabolises Codeine

A

CYP2D6

33
Q

How doe genetics effect Codeine metabolism

A

CYP2D6 activity is decreased in 10-25% of white population and absent in a further 10% so codeine has a reduced effect in this population

CYP2D6 is overactive in 5% of whites so increased risk of respiratory depression

34
Q

What is Morphine metabolised to

A

morphine-6-glucuronide

35
Q

How is Morphine-6-Glucuronide excreted

A

Kidneys

36
Q

Potency of morphine-6-glucuronide vs morphine

A

Morphine is less potent

37
Q

How do we give morphine to patients with 30%< renal function

A

Reduce dose and timing interval

OR use oxycodone instead as it is safer

38
Q

What is Tramadol

A

Weak opioid agonist

39
Q

Potency of TRamadol vs Codeine

A

Stronger in Tramadol

40
Q

What type of drug is Codeine and what metabolises it

A

Prodrug

Metabolised by CYP2D6

41
Q

End-product of Tramadol metabolism

A

O-desmethyl tramadol

42
Q

Secondary effect of Tramadol

A

In analgesia (serotonin and nor-adrenaline reuptake inhibitor)

43
Q

What and why do we take care with Tramadol prescription to people with antidepressants

A

Interacts with SSRIs, antidepressants and MAOs fatally

44
Q

How much of the population can’t metabolise morphine

A

10%

45
Q

What is diamorphine also known as

A

Heroin

46
Q

Three synthetic opioids

A

Pethidine
Fentanyl (potent)
Alfentanil (potent)

47
Q

What happens if we overdose on Buprenorphine

A

No respiratory depression

48
Q

Fastest mode of administration of opioids

A

IV takes 1 minute to travel round the whole body

49
Q

How long does it take for morphine to reach the brain

A

5 minutes

50
Q

How is does self-administered by patients with analgesia

A

Every 5 minutes with lockout

51
Q

Why is salt-administration for analgesia safe

A

Patient will sleep before onset of respiratory depression

52
Q

How long do opioids have an effect for

A

30 minutes

53
Q

Potency of Pethidine vs Morphine

A

10 times weaker

54
Q

Why does Buprenorphine only reach 50% response rates

A

Only a partial agonist (safer)

55
Q

How does mixing Morphine with Naloxone effect efficacy of morphine

A

Reduces it

56
Q

Why do we mix morphine and Naloxone

A

To correct an overdose

57
Q

How does continued morphine use effect Mu receptors

A

Desensitises them

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