Analgesic drugs 1 (part two)

Question 1

What are the effects of fentanyl, a synthetic opiod?

Answer 1

• Highly lipid soluble (fast onset)
• Strong mu receptor agonist
• 80-100x more potent then morphine
• Analgesic commonly used (also in anaesthesia)

Question 2

What are the main Routes of administration for fentanyl?

Answer 2

IV

IM

Transdermal patches** (can deliver at a set __mcg/hour)

Transmucosal lozenges

Nasal/sublingual spray (good for kids)

Sublingual tablets

**disadvantages of transdermal patches: slow onset and inability torapidly change doses

Question 3

What is iontophoresis?

Answer 3

A method of transdermal PCA administration of ionizable drugs in which electrically charged components are propelled throught the skin via an external electric field.

Question 4

What is methadone?

Answer 4

• *Fully synthetic, and well absorbed from all routes of administration**
• -Oral bioavailability 70%
• Rectal
• Subcutaneous
• IV
• sublingual*

Rapid onset of analgesia effect (30-60mins)

No significant cognitive impairment

No euphoria

Safe in renal and liver failure

Question 5

What is methadone used for?

Answer 5

• Chronic pain patients (as its an NMDA antagonist)
• For neuropathic pain
• For opiod withdrawal
• For detox

Question 6

What is tramadol

Answer 6

Synthetic codiene analog, reasonably weak

• oral bioavailability >70%
• weak mu-opioid receptor agonist
• Inhibits uptake of noradrenaline and serotonin (stimulate inhibitory inter-neurons)

Side Effects:
Serotonin Syndrome: agitation, ataxia, incr sweating, diarrhoea, fever (get if you have SSRI antidepressants with tramadol)

Caution in patients with epilepsy history

Question 7

What is codiene?

Answer 7

Can be a single-ingredient or combination drug (eg w paracetamol its co-codamol)​

Treats:

• mild-moderate pain (mu opiod receptors)
• Supresses cough
• antidiarrhoel (can lead to constipation + drowsiness)

​Prolonged use → chance of physical dependance

Question 8

What is codiene metabolised to and how does this vary?

Answer 8

Metabolised by cytochrome P450 2D6 to morphine!

Some patients are ultra-rapid metabolisers → toxic opioid effect

Some patients are slow metabolisers → may not have proper analgesic effect

Question 9

What two types of opioid antagonists are there?

Answer 9

• Naloxone
• Naltrexone (longer duration)

these are devoid of activity at all receptor classes.

Question 10

What is Nitrous Oxide (laughing gas)

Answer 10

• Powerful analgesic, euphoric effec, non addictive
• Rapid onset/offset

Prepped as Entonox (50% N₂O in oxygen)
-maternity, in the field, wound dressing changes.

**may have bone marrow depression if taken excessively for a long time

Question 11

What are CO ANALGESICS

Answer 11

NOT analgesics, used in combo with analgesics to have a better effect.

Primary purpose other then pain relief.

• Tricyclic antidepressants (prolong NA and Serotonin, for chronic pain)
• Anticonvulsants (for neuorogenic pain, facilitate GABA + stop glutamaite)
• Anxiolytics
• Corticosteroids
• Others: ketamine and clonidine