opoid pharmacology

Question 1

what are the simple chemical modifications?

Answer 1

Diamorphine Oxycodone Dihydrocodeine

Question 1

what are natural occurring opioids from the opium poppy?

Answer 1

morphine
codeine

Question 2

what are the routes of administration?

Answer 2

Pharmacokinetics
Oral
Bioavailability
first pass metabolism by the liver

Question 3

describe first pass metabolism

Answer 3

First pass metabolism by the liver – 50% of oral morphine is metabolized by the first pass metabolism. Halve the dose if given IM/ IV etc.

Question 4

how long does a single dose of morphine last for?

Answer 4

3-4 hours

Question 5

A. Sub-cutaneous
B. IM
C. IV
Which will be the fastest?

Answer 5

IV then IM

Question 6

what does opium contain?

Answer 6

morphine and codeine

Question 7

what is the current legislation for controlled drug use ( CDs) ?

Answer 7

Misuse of drugs act 1971

Question 8

what class are opioid drugs?

Answer 8

class A

Question 9

what are the practical issues with CDs?

Answer 9

Secure storage
CD books - two signatures needed

Question 10

how do opioids work?

Answer 10

they use the existing pain pathway
natural endorphins ( endogenous and morphine) and enkephalins
Descending inhibition of pain
Part of the fight or flight response
Never designed for sustained activation

Question 11

what acts via second messengers in the path pathway?

Answer 11

G protein coupled receptors- amplifies the effect

Question 12

what do opioids do?

Answer 12

Inhibit the release of pain transmitters at spinal cord and midbrain - and modulate pain perception in higher centres - euphoria - changes the emotional perception of pain

Question 13

what does sustained activation lead to with opioids?

Answer 13

tolerance and addiction

Question 14

what do kappa agonists do?

Answer 14

cause depression instead of euphoria

Question 15

what agonists are currently used?

Answer 15

μ agonists

Question 16

define potency

Answer 16

whether a drug is ‘strong’ or ‘weak’ relates to how well the drug binds to the receptor, the binding affinity.

Question 17

define efficacy

Answer 17

the concept of full or partial agonists
- does it work

Question 18

define tolerance

Answer 18

down regulation of the receptors with prolonged use. Need higher doses to achieve the same effect

Question 19

define dependence

Answer 19

psychological – craving, euphoria

Question 20

define opioid withdrawal

Answer 20

starts within 24 hours, lasts about 72 hours

Question 21

side effects of opioid use

Answer 21

Respiratory depression
Sedation
Nausea and vomiting
Constipation
Itching
Immune suppression
Endocrine effects

Question 22

how are opioids delivered?

Answer 22

sometimes are delivered epidurals but mostly given systemically

Question 23

where are opioid receptors located?

Answer 23

do exist outside of the pain system
e.g. digestive tract, respiratory control centre

Question 24

where are drug receptors/ opioid receptors?

Answer 24

spinal cord
brain stem

Question 25

how does codeine work?

Answer 25

Codeine is a prodrug - it needs to be metabolised by cytochrome CYP2D6 to morphine to work

Question 26

what is morphine metabolised into?

Answer 26

to morphine 6 glucuronide which is more potent than morphine and is renally excreted. With normal renal function this is cleared quickly

Question 27

what happens to morphine metabolism in renal failure?

Answer 27

In renal failure it will build up and may cause respiratory depression

Question 28

what is tramadol?

Answer 28

Tramadol is a weak opioid agonist, slightly stronger than codeine

Question 29

how does tramadol work?

Answer 29

It is also a prodrug - needs to be metabolised by CYP2D6 to o-desmethyl tramadol to be active

Question 30

what is the secondary effect of tramadol?

Answer 30

in analgesia as a serotonin and nor-epinephrine reuptake inhibitor