Analgesic Drugs

Question 1

Describe the WHO Pain ladder

Answer 1

4. Strong opioid
5. Weak opioid
6. NSAIDs
7. Paracetamol

Question 2

What is the difference between an opiate and opioid?

Answer 2

Opiate - substances extracted from opium

Opioid - any agent that acts on opioid receptors (including endogenous peptides)

Question 3

What descending pathway acts to modify pain?

Answer 3

Supraspinal antinociception

Question 4

Describe the supraspinal antinociception pathway

Answer 4

Peri-aqueductual grey matter sends signals to the locus ceruleus and nucleus raphe magnus which project to dorsal horn of spinal cord and inhibit nociceptive transmission

Question 5

What stimulates the peri-aqueductal grey matter?

Answer 5

Opioids and electrical stimulation

Question 6

Where is the PAG?

Answer 6

Midbrain

Question 7

Where is the locus ceruleus?

Answer 7

Pons

Question 8

Where is the nucleus raphe magnus?

Answer 8

Medulla

Question 9

What does the PAG excite?

Answer 9

Nucleus raphe magnus

Locus coruleus

Question 10

What is the effect of PAG excitation of NRM and LC?

Answer 10

They excite 5HT and NA neurones which project to the dorsal horn and inhibit nociceptive transmission

Question 11

Describe the cellular action of opioids

Answer 11

Inhibit opening of voltage activated calcium channels to prevent release of neurotransmitter
Opens potassium channels to suppress excitation
Inhibits adenylate cyclase

Question 12

Name the three opioid receptors

Answer 12

MU
Delta
Kappa

Question 13

What is the effect of opioids on the respiratory system?

Answer 13

Apnoea - blinding of medullary resp centre to carbon dioxide

Question 14

What is the effect of opioids on the cardiovascular system?

Answer 14

Orthostatic hypertension - reduced sympathetic tone and bradycardia - histamine evoked vasodilation

Question 15

What is the effect of opioids on the GI system?

Answer 15

Nausea, vomiting, constipation, intrabilary pressure

Question 16

What is the effect of opioids on the CNS?

Answer 16

Confusion, euphoria, dysphoria, hallucinations, dizziness, hyperalgesia

Question 17

What can morphine cause in asthmatics?

Answer 17

Degranulation and bronchospasm

Question 18

How do most analgesic drugs work?

Answer 18

Prolonged activation of opioid receptors

Question 19

Name opioid agonists

Answer 19

Morphine 
Diamorphine 
Coedine 
Fentanyl 
Pethidine 
Buprenophine 
Tramadol 
Methadone

Question 20

Name an opioid antagonist

Answer 20

Naloxone

Question 21

When is morphine used?

Answer 21

Severe acute pain

Chronic pain

Question 22

Where is morphine broken down?

Answer 22

Liver

• M3G (inactive)
• M6G (analgesic activity)

Question 23

Name the methods of administration of morphine

Answer 23

IV
IM, SC, oral
Epidural or intrathecal

Question 24

What is another name for diamorphine?

Answer 24

Heroin

Question 25

How is diamorphine different to morphine?

Answer 25

More lipophilic and has a rapid onset of action when administered IV as can enter CNS

Question 26

When is codeine used?

Answer 26

Mild/moderate pain - hepatic metabolism to morphine

Question 27

What are the higher potency derivatives of codeine?

Answer 27

Oxycodone and hydrocodone

Question 28

In addition to pain relief what are the other effects of codeine?

Answer 28

Anti-diarrhoeal | Anti-tussive

Question 29

Describe fentanyl

Answer 29

75-100 times more potent than morphine Given IV to provide analgesia in anaesthetic Transdermal, IV or sublingual delivery

Question 30

When is pethidine used?

Answer 30

Acute pain in labour | Rapid onset

Question 31

What drug can pethidine not be used with?

Answer 31

Monoamine oxidase inhibitors

Question 32

When is buprenorphine used?

Answer 32

Chronic pain with patient controlled injection systems

Question 33

What is the mechanism of action of tramadol?

Answer 33

Weak mu receptor agonist potentiates the descending pathways

Question 34

What disease should tramadol be avoided in?

Answer 34

Epilepsy

Question 35

Where does methadone work?

Answer 35

Weak mu receptor agonist Acts on potassium channels NMDA glutamate receptors 5HT receptors

Question 36

What can methadone be used for?

Answer 36

Terminal cancer | Withdrawal

Question 37

What does naloxone do?

Answer 37

Competitive antagonist of mu receptors and used to reverse opioid toxicity

Question 38

Where do non-selective NSAIDs work?

Answer 38

COX 1 inhibitor

Question 39

Where do selective NSAIDs work?

Answer 39

COX2 induced locally at sites of inflammation

Question 40

Name non-selective NSAIDs

Answer 40

Aspirin Ibuprofen Diclofenac Naproxen

Question 41

Name selective NSAIDs

Answer 41

Etoricoxib Celecoxib Inmiracoxib

Question 42

Name drugs that can be used in neuropathic pain

Answer 42

Gabapentin Pregablin Amitriptyline Carbamazepine

Question 43

How do gabapentin and pregablin work?

Answer 43

Reduce cell surface expression of a subunit of voltage gated calcium channels which are unregulated in damaged neurones

Question 44

What can gabapentin and pregablin be used for?

Answer 44

Pregablin - diabetic neuropathy | Gabapentin - migraine

Question 45

How does amitriptyline work?

Answer 45

Decrease reuptake of noradrenaline

Question 46

Name a sodium channel blocker

Answer 46

Carbamazepine

Question 47

What type of pain can carbamazepine be used for?

Answer 47

Trigeminal neuralgia