Week 15 - Opiate analgesics

Question 1

In addition to the relief of acute severe pain and chronic pain, when else can morphine be used?

Answer 1

Morphine can be used to reduce breathlessness
by reducing the sensitivity of the medulla to hypoxia/hypercapnia and reducing sympathetic innervation.

Question 2

Explain WHO’s three-step ladder.

Answer 2

Level 1 with a non-opioid (NSAID) +/- an adjuvant.

Level 2 adds in a mild opioid such as the opiate codeine +/- an adjunctive.

level 3 adds in a potent opioid such as the opiate morphine +/- adjunctive.

Adjunctives include antidepressants (e.g. amitriptyline), anticonvulsants (e.g. gabapentin), corticosteroids (e.g. dexamethasone), and anxiolytics (e.g. diazepam).

Question 3

What are the three opioid receptors?

Answer 3

mu, delta, and kappa

Question 4

What is the difference between an opioid and an opiate?

Answer 4

Question 5

What should a breakthrough dose of of analgesia be ?

Answer 5

About 1/6 of the total daily regular dose.

Question 6

What receptors does morphine bind do?

What is its mechanism of action?

Answer 6

Morphine is selective for the u-opioid receptor

A presynaptic effect inhibits the opening of calcium channels to reduce neurotransmitter release.

Morphine also has an inhibitory post-synaptic effect opening potassium channels to hyperpolarise the post-synaptic membrane, inhibiting action potential conduction.

Question 7

What is a Intrathecal Opioid Infusion?

Answer 7

Infusing medication directly into this area helps it reach the spinal cord and nerves, where it can control pain or the abnormal muscle contractions that lead to spasticity.

Question 7

What are the unwanted side of effects of morphine ?

Answer 7

• Activating U receptors in other parts of the body.

Causing:

• Constriction of the pupils
• Respiratory depression
• Nausea and vomiting
• Constipation

Question 7

What is codeine used for?

What is the common side effect of this medication?

What type of drug is it ?

What enzyme is involved in its metabolism?

What condition would codeine not work for?

Answer 7

• Used for analgesics and cough suppressant.
• Constipation
• Pro-drug
• CYP2D6
• Genetic polymorphism – poor metabolisers 1/10 won’t work

Question 8

What receptors does oxycodone bind to ?

Which liver enzyme is involved in this ?

Answer 8

• U-opioid receptors.
• Liver active metabolite CYP450 interactions

Question 9

When is Dihydrocodeine used ?

What is the dose given ?

Answer 9

• Defined as weak opioid in moderate to severe pain
• Up to 30mg every 4-6h,

Question 10

What receptor does pethidine bind to ?

When is it used and why ?

Answer 10

u-opioid receptor

Pethidine, however, still retains a use in the acute relief of pain, its onset of action being quicker than morphine, and is therefore used in childbirth.

Question 11

What receptors does loperamide bind to?

Why does it not have analgesic activity?

How does it work?

Answer 11

• U-opioid
• Does not cross BBB
• Decreases activity myenteric plexus (50x morphine) - decreasing G/I motility, slow transit time, enhancing water/ion absorption

Question 12

What is the opiod antagonist ?

Answer 12

Naloxone !!!

Question 13

What is diamorphine also known as ?

Answer 13

Heroin

Question 14

What medication can be given to people with opioid:

• Tolerance
• Physical Dependence
• Psychological Dependence
• Withdrawal Syndrome

Answer 14

buprenorphine

Question 15

What weak U- receptor opioid also inhibits the uptake of noradrenalin and serotonin?

Answer 15

Tramadol - Therefore, it works as an effective antidepressant also.

Question 16

What anticonvulsant is effective in treating trigeminal neuralgia?

What is the mechanism of this drug action ?

Answer 16

Carbamazepine

Sodium channel blocker - prevents firing of action potential.

Question 17

What medication can be used in treating diabetic neuropathy?

Answer 17

Gabapentin