L6 Narcotic (Opoid) Analgesics

Question 1

What was opioid peptides previously known as?

Answer 1

Endorphins, collectively

Question 2

Which opioid receptor subtype is probably the major one?

Answer 2

mu

Question 3

Which opioid receptor subtype results in dysphoria (unease/discomfort)?

Answer 3

kappa

Question 4

Examples of opioid agonists used for analgesia

Answer 4

codeine, morphine, pethidine

Question 5

Examples of opioid agonists used for anaesthetic adjuvant

Answer 5

fentanyl

Question 6

Examples of opioid agonists used for cough suppressant/antitussive

Answer 6

codeine

Question 7

Examples of opioid agonists used for anti-diarrhoeal

Answer 7

diphenoxylate

Question 8

Strong opioid agonists

Answer 8

morphine, methadone, fentanyl, pethidine (meperidine)

Question 9

Moderate opioid agonists

Answer 9

codeine/dihydrocodeine, tramadol

Question 10

Main difference between morphine and methadone/fentanyl?

Answer 10

Morphine has weak delta and kappa agonist properties, but methadone and fentanyl has no significant delta and kappa affinity

Question 11

What is the main difference between methadone and fentanyl?

Answer 11

Methadone is long-acting with a plasma half-life > 24hrs, while fentanyl is short-acting and used as an anaesthetic adjuvant

Question 12

What is a useful application of pethidine (meperidine)?

Answer 12

As an epidural in labour, less likely to remain in neonate due to its shorter duration of action than morphine, especially in neonates

Question 13

What are some side effects of pethidine?

Answer 13

• Hallucinogenic and convulsant effects at high dose: N-demethylated in the liver to norpethidine
• Restlessness rather than sedation
• Antimuscarinic ie. parasympatholytic: dry mouth, blurring of vision but no miosis and less spasm of smooth muscle

Question 14

Contraindication (age group) of opioids

Answer 14

Infants

Question 15

What is an ADR of opioids that gets better with repeated or chronic use?

Answer 15

n/v

Question 16

What is an ADR of opioids that develops with repeated or chronic use?

Answer 16

constipation, due to reduced GI motility

Question 17

What is a diagnostic feature of opioid overdose?

Answer 17

Pinpoint pupils, due to actions in the oculomotor nucleus

Question 18

CI for morphine (or just used in caution)

Answer 18

asthmatics

- can trigger histamine release from mast cells, causing bronchoconstriction

Question 19

ADR of opioids

Answer 19

n/v, constipation, drowsiness
miosis, mydriasis (following hypocia)
urinary retention, postural hypotension and bradycardia, immunosuppressant with LT used
(morphine-specific) urticaria and itching, bronchoconstriction, hypotension

Question 20

Examples of opioid antagonists

Answer 20

naloxone, naltrexone, nalmefene

Question 21

CI of opioid antagonists (or use with extreme caution)

Answer 21

pt with opiate dependency, they can precipitate potentially fatal withdrawal smx

Question 22

Opioid analgesia MOA

Answer 22

plays on endogenous mechanism

• inhibit propagation of pain signals
• alter emotional perception of pain
• elevate the pain threshold?

Question 23

Sites of opioid receptors regulating pain (3)

Answer 23

• peripheral nociceptive terminals
• spine
• brain