9. Drugs for Pain

Question 1

What is the difference between A and C pain fibres?

Answer 1

A is fast, sharp pain

C is slow, dull ache

Question 2

What are the endogenous opioids?

Answer 2

Endorphins
Enkephalins
Dynorphins

Question 3

What receptors do endorphins bind to?

Answer 3

Mu

Question 4

What receptors do enkephalins bind to?

Answer 4

Delta and mu

Question 5

What are the types of enkephalins?

Answer 5

Met-

Leu-

Question 6

What receptors do dynorphins bind to?

Answer 6

Kappa

Question 7

What are the types of dynorphins?

Answer 7

A and B

Question 8

What kind of receptors are opioid receptors?

Answer 8

GPCRs

Question 9

What is the MOA of opiates?

Answer 9

Bind to GPCR and inhibit adenylate cyclase to reduce cAMP> close Ca++ channels or open K+ channels> reduced NT release

Question 10

What are the inhibitory neurotransmitters?

Answer 10

GABA (brain)

Glycine (peripheral)

Question 11

What type of drug is morphine?

Answer 11

Strong opioid agonist

Question 12

What are the effects of morphine?

Answer 12

Increase pain threshold without loss of consciousness

Euphoria at M or dysphoria at k

Question 13

What are the adverse effects of opiates?

Answer 13

Respiratory depression, sedation
Pinpoint pupils in overdose
Nausea, vomiting, constipation
Tolerance, dependence

Question 14

What is methadone used for?

Answer 14

Treatment of opiate addiction

Question 15

What increases the efficacy of fentanyl compared to morphine?

Answer 15

Has a higher lipophilicity so it can cross the BBB much more rapidly

Question 16

What non-analgesic effect does codeine have?

Answer 16

Antitussal

Question 17

Name an analogue of codeine

Answer 17

Tramadol

Question 18

What is the active metabolite of tramadol?

What is its other effects?

Answer 18

Dematralodol

Inhibits reuptake of NA and serotonin

Question 19

What adverse effects are associated with tramadol?

Answer 19

Increased risk of seizures, serotonin syndrome and dependence

Question 20

Name 2 opioid antagonists

Answer 20

Naloxone

Naltrexone

Question 21

What are the functions of opioid antagonists?

Answer 21

Naloxone in overdoses

Naltrexone in withdrawal

Question 22

What kind of drug is buprenorphine?

Answer 22

Mixed agonist; also has antagonist properties

Question 23

Why is buprenorphine used?

Answer 23

In withdrawal it reduces high that other opiates would give

Less euphoria, sedation, milder withdrawal

Question 24

Which opiate properties is tolerance developed to?

Answer 24

Analgesia
Euphoria
Respiratory depression
Emesis

Question 25

What opiate properties is tolerance not developed to?

Answer 25

Pupillary constriction | Constipation

Question 26

What is neuropathic pain?

Answer 26

Due to nerve damage caused by toxins, infections, autoimmunity or tumours Numbness along path of nerve, burning or heavy sensation Anticonvulsants and antidepressants used to treat

Question 27

What is the MOA of anticonvulsants?

Answer 27

Inactivate Na+ channel to reduce neuronal excitability | Gapabentin acts on Ca++ channels

Question 28

Name 3 anticonvulsants that act on Na+ channels

Answer 28

Carbamazepine Lamotrigine Phenytoin

Question 29

What is the MOA of antidepressants?

Answer 29

Monoamine reuptake inhibitors

Question 30

Name 2 topical anaesthetics

Answer 30

Lidocaine | Benzocaine

Question 31

How do topical anaesthetics work?

Answer 31

Block Na+ preventing APs

Question 32

How is systemic toxicity from an injected anaesthetic avoided?

Answer 32

Co-administer a vasoconstrictor to avoid seeping into vessels eg. adrenaline

Question 33

Name 2 general anaesthetics that target GABA channels

Answer 33

Barbituates and benzodiazepines

Question 34

What channel does ketamine block?

Answer 34

NMDA (glutamate)

Question 35

What is the limitation of halothane as an inhaled anaesthetic?

Answer 35

Must be given with oxygen

Question 36

What is the limitation of desflurane?

Answer 36

Rapidly excreted

Question 37

What channel does nitrous oxide block?

Answer 37

NMDA

Question 38

What used to be used to describe the efficacy of inhaled anaesthetics?

Answer 38

Blood: gas partition coefficient Blood: brain partition coefficient

Question 39

What is now used to calculate the potency of inhaled anaesthetics?

Answer 39

Minimum alveolar concentration

Question 40

What is the minimum alveolar concentration?

Answer 40

Volume of anaesthetic in inspired air that provides analgesia to 50% of population