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aa bds m6 - therapeutics > 6. Analgesia - Codeine > Flashcards

6. Analgesia - Codeine Flashcards

1
Q

When and where were opiates first isolated from?

A

1803 from the white poppy (papaver somniferum)

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2
Q

What is considered the most potent opiate?

A

morphine

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3
Q

What are opiates referred to as acting on?

A

central acting analgesia

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4
Q

What do opiates act on?

A

µ, δ and κ opioid receptors

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5
Q

What kind of metabolism do opiates undergo?

A

1st pass metabolism, conjugated in the liver

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6
Q

What is the approx. half life of opiates?

A

3 hours

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7
Q

What kind of pain is morphine used for?

A

acute severe pain - continuous dull (rather than sharp intermittent)

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8
Q

What CNS effects does morphine have?

A

drowsiness, sedation and euphoria

(does not effect touch, pressure, vision, hearing)

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9
Q

What are some of the unwanted effects of morphine?

A
  • nausea and vomiting (intitial)
  • urticaria/pruritis
  • respiratory depression
  • constipation (GI motility)
  • eye signs (mitosis - pinpoint pupils)
  • confusion in the elderly
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10
Q

Why does morphine commonly cause nausea and vomiting?

A

due to direct stimulation of the chemoreceptors in the medulla and as such often need an antiemetic

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11
Q

What is the oral dosage for morphine?

A

10-30mg every 4 hours as required

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12
Q

What is the IV dosage for morphine?

A

2.5-15mg/70kg / 4 hours

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13
Q

What is the IM dosage of morphine?

A

10mg, works in 30 mins and lasts for 4-5 hours

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14
Q

What is the SC dosage of morphine?

A

5-20mg/70kg every 4 hours

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15
Q

What tends to be the max dose of morphine given per 24 hours?

A

100mg in 24 hours

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16
Q

What are the contraindications and special considerations for morphine?

A
  • dependence
  • ulcerative colitis + AAC
  • suspected head injury
  • acute alcoholism
  • reduced respiratory reserve
  • upper airway obstruction
  • acute asthma
  • poisoning or toxins (constipation will stop clearing of this)
  • hepatic and renal insufficiency
  • hypersensitivity to opiates
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17
Q

What are the signs of an opioid overdose?

A
  • asleep and difficult to wake
  • low resp. rate
  • low BP
  • pupil constriction which tends not to respond to light
  • cold and clammy skin
  • flaccid skeletal muscle including tongue with resultant airway compromise
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18
Q

How would you treat an opioid overdose?

A

establish airway and administer naloxone 04mg IV ever 2-3mins

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19
Q

What are codeine/dihydrocodeine?

A

naturally occurring opioids

20
Q

How are codeine and dihydrocodeine taken?

A

oral opioid

21
Q

What are codeine and dihydrocodeine antagonists at?

A

µ opioid receptors

22
Q

What kind of pain are codeine and dihydrocodeine used for?

A

mild to moderate acute and chronic pain

23
Q

What is codeine/dihydrocodeine often used in combination with?

A

paracetamol - cocodamol/cohydramol

24
Q

What causes codeine to be analgesic?

A

codeine alone doesn’t have much analgesic effect, but it is metabolised in the liver to give about norcodeine and 10% morphine which is primarily responsible for the analgesic activity

25
Q

Dose to dose, what is the potency of codeine compared to morphine?

A

8-10% the potency of morphine

26
Q

Where is codeine metabolised?

A

the liver

27
Q

What is the half life of codeine?

A

3 hours

28
Q

How long does the analgesic effect of codeine lasts?

A

2-4 hours

29
Q

Why do some patients get little analgesic efficacy from codeine?

A

about 7% of the population lack the CYP450 2D6 receptors responsible for the drug biotransformation in the liver

30
Q

What are ‘ultrametabolisers’ of codeine?

A

group of people with high efficiency of turning codeine into morphine and some of these patients start to feel very unwell with nausea and vomiting due to higher levels of morphine

31
Q

What are the contraindications and side effects of codeine?

A

mimic those of morphine but at a lower level:
- nausea
- hypotension
- urticaria/pruritis
- respiratory (low chance)
- constipation (when used longer term)
- dependence/tolerance (not a high chance)

32
Q

What is the standard adult dose of codeine?

A

30-60mg 4-6 hourly
(maximum 240mg in 24 hours)

33
Q

What are the indications and uses of codeine?

A
  • mild-moderate pain
  • postoperative pain
  • step 2 on WHO ladder as an opiate adjunct
  • NSAIDs contraindicated
  • antitussive
  • antidiarrhoeal
34
Q

Is codeine useful for dental pain?

A

not so much on its own but yes in combination with paracetamol (cocodamol)

35
Q

What are the principle interactions of codeine?

A
  • alcohol
  • antihistamines
  • anxiolytics and hypnotics
  • antipsychotics
36
Q

What can the interaction of codeine with alcohol cause?

A

enhanced hypotension

37
Q

What can the interaction of codeine with antihistamines cause?

A

increased sedative effect

38
Q

What can the interaction of codeine with anxiolytics and hypnotics?

A

enhanced sedative effect

39
Q

What can the interaction of codeine with antipsychotics cause?

A

increased sedative effect and enhanced hypotension

40
Q

Why must you beware of giving codeine to a patient with diarrhoea of an unknown origin?

A

patient may have ingested a toxin etc or have the likes of a c diff infection that they’re body is trying to clear, and the antidiarrhoeal effects of codeine would be undesirable

41
Q

What special considerations should be made when giving codeine to certain patients?

A
  • Beware in Diarrhoea
  • Constipation (GI issues)
  • 7% Caucasian Population uneffective
  • ‘ultrametabolisers’
  • Dependency (long term use)
42
Q

What are some of the combined preparations of codeine available?

A
  • Cocodamol=paracetamol/codeine (most common)
  • Codyramol=paracetamol/dihyrocodeine
  • Co-proxamol=paracetamol/ dextropropoxyphene
  • Cocodaprin=aspirin/codeine
  • Solpadeine, solpadol, paracodol, tylex (on public sale)
43
Q

What drugs may need to be taken alongside opioids?

A

anti-emetics and laxatives

44
Q

What is ‘NNT’?

A

the number of patient who need to receive the active drug for one to achieve at least 50% relief o pain compared with placebo over a 4-6 hour treatment period

45
Q

What do more effect drugs have an NNT of, and what does this mean?

A
  • more effect drugs have a lower NNT - of just over 2
  • in essence this means that for ever two patient who receive the drug one patient will get at least 50% relief because of the treatment

aa bds m6 - therapeutics (6 decks)

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