CPTP 3.20 Neuropharmacology 5 Opioids Flashcards Preview

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Flashcards in CPTP 3.20 Neuropharmacology 5 Opioids Deck (26)
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1

What are the immediate concerns associated with excessive opiate use?

Too much opiate can suppress the pons and medulla, causing suppression of autonomic function (i.e. breathing)

Miosis and unconsciousness can also occur

2

How do opioid receptors effect neuronal activity?

What can this often lead to?

• Increases potassium conductance, hyperpolarising neurones
• Inhibits calcium entry, preventing neurotransmitter release

Inhibition of GABA-ergic interneurones, thus disinhibition of downstream neurones can occur (resulting in the increase in dopamine, etc which creates the euphoric feeling)

3

What are the desirable effects of opioids

• Analgesia
• Euphoria
• Sedation
• Cough suppression

4

What are the adverse effects of opioids?

• Constipation
• Respiratory depression
• Histamine release & Immunosuppression
• Nausea and vomiting
• Tolerance and dependence

5

Where are opioid receptors with antinociceptive effects found?

• Limbic areas
• Medulla
• Periaqueductal gray
• Dorsal horns

6

Which opioid receptors are there?

Mu (μ) receptors
• Analgesic effects in brain
• Respiratory depression
• Physical dependence

Kappa (κ) receptors
• Analgesic effects in spinal cord
• Respiratory depression
• Physical dependence

Delta (δ) receptors
• CNS and enkephalin effects
• No dependence or respiratory depression
• Aversion

7

Describe the endogenous opioids which act on each opioid receptor subtype, and what they are formed from.

Mu (μ) receptors
• Beta-endorphin
• Formed from proopiomelanocortin

Kappa (κ) receptors
• Dynorphin A and B
• Formed from prodynorphin

Delta (δ) receptors
• Met-enkephalin and leu-enkephalin
• Formed from proenkephalin

8

Name the opioid agonists in the student formulary.

• Codeine
• Morphine
• Diamorphine
• Tramadol

9

What can be administered to individuals only after a long amount of time after quitting opioids after an addiction, to help reverse the effects?

Why is this wait necessary and what does the drug do?

What other use does this drug have?

Naloxone
• Opioid competitive antagonist

Must wait a long time otherwise a potentially fatal 'cold turkey' event could occur

Treating morphine overdose

10

Which opioid receptor subtypes are targetted by:
1) Morphine
2) Diamorphine

1) mu and delta
2) mu and delta

11

Describe the metabolisation of morphine

• Metabolised by glucuronidation into the active metabolite morphine-6-gucuronide
• Extensive first pass metabolism
• Active duration of 6 hours (half life 3h)

12

What are the risk groups for morphine administration?

• Elderly (reduced metabolism)
• COPD
• Liver and renal disease

13

What is morphine used for?

Moderate to severe pain

Acute heart failure

14

Why is morphine used for acute heart failure?

• Relieves pain
• Reduces anxiety
• Dilates blood vessels

15

How can morphine be administered?

• Oral
• Parenteral (IV, IM, SC)
• Epidural

16

What is heroin's medical name?

Diamorpine

17

What is the chemical name of diamorphine?

Describe the pharmacodynamics of diamorphine

Diacetylmorphine

It is deacetylated into morphine, and then follows the same pharmacokinetics and pharmacodynamics as morphine:
• Metabolised by glucuronidation into the active metabolite morphine-6-gucuronide
• Extensive first pass metabolism
• Active duration of 6 hours (half life 3h)

18

How can diamorphine be administered?

Parenteral (IV, SC, IM)

19

What is methodone?

An opioid agonist with the same pharmacology as morphine but a much higher half life of 24 hours which is used in substitution therapy in heroin addicts.

Used to prevent the onset of withdrawal states

20

How is methodone administered?

Orally

21

What is codeine used for?

Weak oral opiate for:
• Mild pain
• Diarrhoea
• Anti-tussive (suppresses coughing)

22

Which opioid is used for chronic pain?

Recall its pharmacodynamics

Tramadol
• μ-opioid agonist
• Serotonin and noradrenaline reuptake inhibitor

23

What is the benefit of tramadol's inhibition of serotonin and noradrenaline reultake?

Opioid agonists work by decreasing activity of inhibitory neurones, thus disinhibiting downstream serotonergic and noradrenergic neurones (decreased activity of which causes pain and poor feeling of wellbeing i.e. not euphoria)

This effect is synergised by tramadol's reuptake inhibition as the downstream serotonergic and noradrenergic activity is heightened

This decreases the dose of opioid agonists needed for good efficacy

24

Describe the two main addiction mechanisms

• Chasing the dragon - due to tolerance users increase the dose needed to attain the same high
• Avoidance of withdrawal

25

Disinhibition in what brain region leads to increased dopamine release where?

What does this cause?

Disinhibition in ventral tegmental area leads to increased dopamine release in the nucleus ambiguus

Euphoria, and eventually dependence

26

Why can be effective in reducing cold turkey symptoms? Why

α-2 adrenoreceptor agonists

Locus coeruleus activity is heightened during cold turkey symptoms