Opioids

Question 1

What is nociception?

Answer 1

Non conscious neural traffic due to trauma or potential trauma to tissue

Question 2

What is pain?

Answer 2

Complex, unpleasant awareness of sensation modified by experience

Question 3

How is pain signalled?

Answer 3

Nocicpetors stimulated 
Release of substance P + glutamate
Afferent nerve stimulated
Fibres decussate
Action potential ascends
Synapse I thalamus
Project to post-central gyrus

Question 4

What modulates pain peripherally?

Answer 4

Substantia gelatinosa

Question 5

What modulates pain centrally?

Answer 5

Peri aqueductal grey

Question 6

How is pain felt peripherally?

Answer 6

Stimulate AP - lamina 1+5 -> thalamus

Inhibits substantia gelatinosa

Question 7

How is pain modulated peripherally?

Answer 7

‘Rub it’

Aδ stimulate substantia gelatinosa
Inhibits lamina

Question 8

How is pain felt centrally?

Answer 8

Thalamus stimulates cortex

Cortex inhibits peri aqueductal grey

Question 9

How is pain modulated centrally?

Answer 9

Peri aqueductal grey overrides inhibition

Modulated by

• 5HT
• endogenous opioids

Question 10

What are the endogenous opioids?

Answer 10

Enkephalins
Dynorphins
B-endorphins

Question 11

What are the receptors for opioids?

Answer 11

GPCRS

• μ (MOP)
• δ (DOP)
• K (KOP)

Question 12

Where are μ receptors found?

Answer 12

Supraspinal

GI tract

Question 13

What is the effect μ receptor stimulation?

Answer 13

Decreased cAMP
Outward flux of potassium
Hyperpolarisation
Substance P release

Question 14

What endogenous opioids act on μ receptors?

Answer 14

Enkephalins

B-endorphins

Question 15

What happens when μ receptors are stimulated?

Answer 15

Analgesia
Depression 
Euphoria 
Dependence
Respiratory sedation

Question 16

Where are δ receptors found?

Answer 16

Wide distribution

Question 17

What is the effect of δ receptor stimulation?

Answer 17

Decreased cAMP
Influx of calcium
Hyperpolarisation
Substance P release

Question 18

What endogenous opioids act δ receptors?

Answer 18

Enkephalins

Question 19

What happens when δ receptors are stimulated?

Answer 19

Analgesia
Inhibit dopamine
Modulate μ receptors

Question 20

Where are K receptors found?

Answer 20

Spinal cord
Brain
Periphery

Question 21

What is the effect of K receptor stimulation?

Answer 21

Decreased cAMP 
Efflux of potassium 
Influx of calcium 
Hyperpolarisation 
Substance P release

Question 22

What endogenous opioids act on K receptors?

Answer 22

Dynorphins

Question 23

What happens when K receptors are stimulated?

Answer 23

Analgesia
Diuresis
Dysphoria

Question 24

What is the WHO analgesic ladder?

Answer 24

Simple analgesia
Weak opioid
Strong opioid

Question 25

What is a weak opioid?

Answer 25

Codeine

Question 26

What is a strong opioid?

Answer 26

Morphine | Fentanyl

Question 27

What is a partial opioid agonist?

Answer 27

Buprenorphine

Question 28

What is an opioid antagonist?

Answer 28

Naloxone

Question 29

What routes can be used to administer morphine?

Answer 29

``` PO IV IM SC PR ```

Question 30

What is the mechanism for morphine as an analgesia?

Answer 30

Strong affinity for μ receptors Release of enkephalins + B-endorphins

Question 31

What is the mechanism for morphine as an anti-diarrhoeal?

Answer 31

Decreases tone of longitudinal and circular smooth muscle Reduces peristalsis Decreases colonic mass movement

Question 32

What are the side effects of morphine?

Answer 32

Respiratory depression Emesis Histamine release Constipation

Question 33

What are the indications for fentanyl?

Answer 33

Analgesia | Anaesthesia

Question 34

What are the routes of administration for fentanyl?

Answer 34

``` IV Epidural Transdermal Buccal Intrathecal ```

Question 35

What is the mechanism of fentanyl?

Answer 35

High affinity for μ receptor

Question 36

What are the side effects of fentanyl?

Answer 36

Respiratory depression Constipation Vomiting

Question 37

What are the indications for codeine?

Answer 37

Analgesia Anti-diarrhoeal Cough depressant

Question 38

What are the routes of administration for codeine?

Answer 38

PO | IM

Question 39

What is the mechanism of codeine?

Answer 39

Activation of μ receptors 1/10th potency of morphine

Question 40

What are the side effects of codeine?

Answer 40

Constipation | Respiratory depression

Question 41

What are the indications for buprenorphine?

Answer 41

Analgesia | Opioid addiction adjunct

Question 42

What are the routes of administration for buprenorphine?

Answer 42

Transdermal IM Sublingual

Question 43

What is the mechanism of buprenorphine?

Answer 43

High affinity for μ receptor - low kd - partial agonist Antagonist at K receptor

Question 44

What are side effects of buprenorphine?

Answer 44

Respiratory depression Hypotension Nausea Dizziness

Question 45

What is the indication for naloxone?

Answer 45

Competitive antagonism of opioid

Question 46

What are the routes of administration for naloxone?

Answer 46

IV | IM

Question 47

What is the mechanism of naloxone?

Answer 47

Competitively blocks μ recptors Greater affinity than morphine

Question 48

What are the side effects of naloxone?

Answer 48

``` Arrhythmias Dizziness Headache Hypertension Nausea ```

Question 49

How does opioid tolerance occur?

Answer 49

Body upregulates receptors so higher dose needed to cause an effect

Question 50

What is given to reduce symptoms of opioid withdrawal?

Answer 50

Methadone

Question 51

What are the signs of an opioid overdose?

Answer 51

Vomiting Hypotension Respiratory depression

Question 52

How is an opioid overdose managed?

Answer 52

Naloxone