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Flashcards in Pain management Deck (9)
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1
Q

What is the conversion ratio of oral to subcut morphine?

A

Approximatley 2:1

Example

  • Morphine 5mg sub cut x6 per day = morphine 30mg sub cut per day
  • Approx. morphine 60mg orally per day
2
Q

What is the conversion ratio of dihydrocodeine to morphine?

A

Approximately 10:1

Example

  • Dihydrocodeine 60mg 4x day = dihydrocodeine 240mg per day
  • Equivalent to 24mg morphine
3
Q

How is morphine metabolised?

A

Morphine is metabolised in the liver by glucuronidation to morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G). M3G is probably inactive. M6G has analgesic properties but is also responsible for the toxicity.

4
Q

Where are morphine metabolites excreted?

A

Kidney

5
Q

What are clinical features of opiate toxicity?

A
  • Altered consciousness
  • Confusion
  • Vivid dreams
  • Pseudohallucinations/hallucinations
  • Myoclonus
  • Hyperalgesia and whole body allodynia.
6
Q

What are pseudohallucinations?

A

Disorders of perception that resolve when attention is brought to bear e.g. thinking there is a person in the bedroom with you but then realising it is just the dressing-gown hanging on the door

7
Q

What is myoclonus?

A

Muscle twitching - a sign of neuromuscular hyperexcitability. Usually more evident when the patient is relaxing.

8
Q

What is hyperalgesia?

A

Severe pain experienced from a mildly painful stimulus

9
Q

What is allodynia?

A

Pain experienced with non painful stimulus. Even light touch of the skin can be intolerable. Nurses may report this as they struggle to provide the patient with personal care.