8. Opiates Flashcards Preview

ESA 4- Clinical Pharmacology > 8. Opiates > Flashcards

Flashcards in 8. Opiates Deck (10)
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1
Q

Describe the ‘pain pathway’.

A

i. Peripheral nociceptors sense trauma…
ii. AP transmission along peripheral n. C fibres (slow unmyelinated) and A fibres (fast myelinated) which pass through dorsal root of spinal nerve…
iii. synapse in dorsal horn with neurone which ascends in spinothalamic tract…
iv. synapses in thalamus with neurones which extend to primary sensory cortex.

2
Q

Name the 4 main classes of analgesics and their main indications.

A
  1. PARACETAMOL
    - 1st line agent for mild-moderate pain (e.g. headache)
  2. NSAIDs (e.g. ibuprofen)
    - mild-moderate pain, esp. MSK related as also anti-inflammatory
  3. OPIOIDS (e.g. codeine/morphine)
    - moderate-severe pain, e.g. cancer, chronic, post-op, burn pains
  4. NEUROPATHIC AGENTS
    - nerve pain, e.g. diabetic neuropathy, trapped nerves, chronic pain
3
Q

What are the opioid Rs and what is their function?

A

GPCRs (Gi) located at synapses (e.g. in spinal cord dorsal horn) that act to reduce pain sensation when activated by ligand: inhibit AC… decreases cAMP…

  1. on pre-synaptic terminal - reduce Ca2+ influx in response to AP… decreases release of excitatory NT (e.g. glutamate, substance P)
    2. post-synaptic terminal - increase K+ efflux… post-synaptic hyperpolarisation… inhibits neuronal activity
4
Q

name the 3 main opioid Rs and their effects

A

µ - mu: analgesia (+ euphoria)
δ - delta: analgesia (+ dysphoria)
K - kappa: analgesia (sedation)

5
Q

name the 3 main endogenous opioids

A
  • endorphins
  • enkephalins
  • dynorphins
6
Q

name acute, chronic and non-analgaesic indications for opioids.

A

Acute:

  • trauma and burns
  • perioperative
  • MI

Chronic:

  • refractory pain
  • malignancy

Non-analgesic:

  • cough suppression
  • manage diarrhoea
  • breathlessness
7
Q

Name 6 ADRs of opiates.

A
  1. constipation
  2. confusion and reduced conscious level
  3. respiratory depression
  4. nausea and vomiting
  5. constricted pupils
8
Q

Name 2 consequences of long-term opioid use.

A
  1. tolerance: P needs increasing dose of opiate to have same analgesic effect
  2. dependence/addition: P gets withdrawal symptoms on stopping opiate
9
Q

Suggest examples of opiate types.

A
  • oral codeine - metabolised to morphine (10x weaker)
  • morphine - oral tablet/liquid, IV, SC
  • fentanyl - patch
  • oxycodone (often used in cancer pain/renal failure)
10
Q

Name an opiate antagonist and its indication.

A

NALOXONE - opiate overdose/toxicity