Analgesic Drugs 1: Opiates and Opioids

Question 1

What sort of pain do opioids/opiates deal with?

Answer 1

Nociceptive and inflammatory pain

Question 2

Possible ways of administering opioids

Answer 2

Orally
Parenteraly: intramuscular, intravenous
transmucosal
transdermal

Question 3

Opiates vs opioids

Answer 3

Opiates are the narcotic analgesic derived from the opium plant naturally

Opioids are narcotic analgesics made synthetically, not found in nature

Question 4

Commonly used opioids

Answer 4

Morphine; fentanyl; pethidine; codeine; methadone

Question 5

Opioid receptors

Answer 5

Are presynaptic receptors that belong to the G protein coupled family of receptors.

Some post synaptic receptors

Question 6

Mechanism of action of opioids

Answer 6

1) Activates G proteins causing inhibition of adenylate cyclase. This causes a decrease in Ca2+ channel permeability, so transmitters are not released
2) On post synaptic receptors, increase K+ conductance, causing hyperpolarisation, so a decreased response

Question 7

What are the three kinds of opioid receptors?

Answer 7

Mu, kappa and delta found in the CNS

Mu-2 evokes a lot of responses (euphoria, analegesia)

Question 8

Opioid receptor synthesis

Answer 8

Tissue damage occurs, causing the dorsal root ganglion to synthesise the receptors and place themselves along the axons

Question 9

Opioid receptor agonists and antagonists, partial agonists

Answer 9

Agonists: morphine, pethidine, fentanyl but to different receptors at different affinities

Antagonists: Naloxone

partial agonists: bup re morphine

Question 10

Adverse effects of opioids

Answer 10

Resp depression; drowsiness; constipation; nausea/vomiting; bradycardia, hypotension (morphine)

Question 11

Natural opiates

Answer 11

Morphine and codeine

Question 12

Semi-synthetic opioids

Answer 12

Bup-re-norphine
Heroin
Oxycodone

Question 13

Synthetic opioids

Answer 13

Fentanyl
Pethidine
Methadone
tramadol

Question 14

Endogenous opioids

Answer 14

endorphins (mu); endomorphins (mu); enkephalins; dynorphins

Question 15

What are used to manage opioid withdrawal and some adjunctives

Answer 15

Metahodone and bup-re norphine
with
Clonidine (reduce autonomic response)
promethazine for vomiting
diazepam for muscle spasms
anti diarrheal

OR rapid opiate detoxification, us of high doses of naltrexone under GA

Question 16

Details about MORPHINE
dynamics and kinetics
eye?
note bioavailability 25%

Answer 16

Powerful analgesia
cough suppression
pin point pupil miosis
euphoria
Large volume of distribution (1/3 boud to plasma proteins)
3 hour half life
low lipid solubility (slow onset long duration)

Question 17

Morphine metabolism

Answer 17

M3G

M6G which is potent analgesic, long half life

Question 18

Pethidine details: side effects etc

bioavailability 50%

Answer 18

Synthetic
Tachycardia; dry mouth, miosis less marked
high lipid solubility so fats onset

Question 19

Metabolism of pethidine note

Answer 19

Metabolism product norpethidine has a long half life and can cause renal failure, cause hallucinations and seizures

Question 20

Fentanyl

Answer 20

High lipid sol. - fast onset
mu receptor agonist strong
80-100 times more potent.
Normally IV or transdermal patches

Question 21

Methadone

Answer 21

Well absorbed from all routes oral is common
rapid onset of analgesia
no cognitive impairment or euphoria

Can be used for chronic pain and neuropathic pain due o NMDA receptor antagonism

Question 22

Tramadol

Answer 22

Oral administration good
Inhibits uptake of noradrenaline and serotonin
Can cause serotonin syndrome in conjunction with other drugs suchs as SSRI’s

Question 23

Nitrous oxide: preparation; onset; effects

Answer 23

Prep: entonox (half N2O and O2)in birth,wund dressing change
Powerful analgesic, rapid onset and offset
Euphoric; not addictive