7.2 Opiods

Question 1

How do opiods work?

Answer 1

They prevent the release of substance P in Periphery

and are psychoactive on the CNS

Question 2

Examples of opiods?

Answer 2

Morphine, Oramorph
Codeine
Methadone

Question 3

What are some endogenous opiods?

Their precursors?

Answer 3

Enkephalins - Proenkephalin
Endorphins - POMC
Dynorphins - Prodynorphins

Question 4

What receptors do opiods act on?

Answer 4

Mew
Delta
Kappa

Question 5

What is the main opiod receptor?

Answer 5

Mew

Question 6

What does the Mew Opioid Receptor do?

Location?

Answer 6

Mostly in Periaqueductal Grey (supraspinal) and cortex
Analgesic
It activates K+ channels to hyperpolarise synapses, prevent pain signals from being transmitted/raises threshold
MAIN EFFECTOR OF OPIODS, Morphine

Question 7

What does the Delta Opioid Receptor do?

Location?

Answer 7

Widely distributed

Decreases cAMP, so fewer NT released

Question 8

What does the Kappa Opioid Receptor do?

Location?

Answer 8

In Spinal cord

Inhibits Ca2+ channels

Question 9

What are the ADRs of M and D Opioid receptors?

Answer 9

Dependence

Respiratory Depression

Question 10

What is the Main ADR of Kappa Receptors?

Answer 10

Confusion (Dysphoria)

Question 11

What are some ADRs of Mew Receptors?

Answer 11

Resp Depression
Hypotension (vasodilation)
Dependence
Tolerence
Nausea and Vomiting (acts on vomiting centre of brain)
Miosis
Drowsiness
Constipation (inhibits gut nerve transmission)

Question 12

What are some Opioid Agonists?

Answer 12

Morphine
Codeine
Methadone

Question 13

What are some Opioid Antagonists?

Answer 13

Naloxone

Question 14

How is Morphine metabolised?

Answer 14

Straight to Phase 2 glucoronidation
Creates active metabolite (M6G) and M3G
Has long half life due to active metabolite

Question 15

What are the properties of morphine?
Half life?
Bioavailability?

Answer 15

Poor lipid solubility –> poor oral bioavailability

Long half life due to active metabolite

Question 16

What is Diamorphine?

Answer 16

Heroin!
More lipid soluble (has acetyl group) so crosses BBB
Short half life but converted into morphine
Good way to quickly get analgesia to CNS

Question 17

What is Codeine?
Given?
Bioavailability?

Answer 17

Mild analgesic
50% oral bioavailability
Prodrug to morphine, converted by P450 enzyme (some lack!!!)

Question 18

When do we use Opioid Agonists?

Answer 18

Anasthesia - fentanyls
Dependence - methadone
Analgesia- good for visceral, moderate pain, pallative care
Diarrhoea - morphine+clay

Question 19

What might you use in pregnancy?

Why is it a bit sketchy?

Answer 19

Labour Pain - Pethidine

But it is potent, can cause convulsions, no repeat doses, seems silly….

Question 20

When do we use opioid antagonists?

Examples?

Answer 20

To treat an overdose or dependence
Prevents respiratory depression
Naloxone (IV) Naltrexone

Question 21

Opioids are controlled drugs, what does this mean?

Answer 21

Must put your name and address on it, sign, date. Must write in figures and letters the form and dose given

Question 22

When might you use an opioid antagonist/agonist?

Answer 22

Analgesia without euphoria (antagonises Mew)

Nalbuphine

Question 23

What is NOP?

Answer 23

New endogenous receptor

Has nociceptin which binds to trasmit pain

Question 24

What is NOP?

Answer 24

New endogenous receptor

Has nociceptin which binds to transmit pain