Opioids

Question 1

What is the mechanism of action of tramadol?

Answer 1

Weak mu receptor partial agonist

Inhibitor of noradrenaline and serotonin reuptake to have anti-nociceptive effects

Question 2

How long until the onset of analgesia in IV fentanyl?

Answer 2

Minutes

Question 3

What is the mechanism of action of fentanyl?

Answer 3

Same as morphine

Question 4

What are the non-analgesic effects of morphine?

Answer 4

Sedation

Anxiolysis

Cough suppression

Reduced gut motility

Question 5

What is the normal IV dose of morphine?

Answer 5

2.5-5mg

Question 6

How is tramadol administered and dosed?

Answer 6

Oral - immediate acting - 50 to 100mg

• Slow release - 12hour - 50, 100, 200, 300
• Slow release - 24hours - 100, 200, 300

IV 100mg / 2mg ampule

Question 7

What are the routes of administration of morphine? Compare their time to peak analgesic effect

Answer 7

Oral - 60 minutes

IM - 30-60 minutes

SC - 50-90 minutes

IV - 20 minutes

Epidural and intrathecal

Question 8

What are some adverse effects of tramadol?

Answer 8

Seizures

Serotonin syndrome

Others as with morphine but much less severe

Question 9

What are some indications for codeine?

Answer 9

Mild to moderate pain

Antitussive

Antidiarrhoeal

Question 10

What are some indications for morphine use?

Answer 10

Moderate to severe pain

Anxiolysis - APO

Adjunct analgesia in general anaesthetic and intubation

Palliative care

Question 11

What is serotonin syndrome?

Answer 11

A constellation of symptoms associated with excess serotonin due to iatrogenic causes

• Seizures
• Arrhythmias
• Rhabdomyolysis
• DIC
• Acute renal failure
• Respiratory failure

Question 12

What are some contraindications for tramadol?

Answer 12

Lower the threshold for seizures therefore - epilepsy, those at risk of epilepsy

Other serotonergic drugs - eg SSRIs

Question 13

Compare fentanyl with morphine

Answer 13

Fentanyl is 100x more potent, 100ug is equivalent to 10mg

More stable affects in the CVS

Faster acting cf to morphine

Question 14

What is the mechanism of action of morphine?

Answer 14

Mimics endogenous opioids in acting on opioid receptors (predominantly mu, but also have action on kappa and delta) in the CNS, and PNS to block all forms of pain

Specifically by:

Presynaptic inhibition of neurotransmitter release for C-fibre terminals

Postsynaptic inhibition of evoked nociceptive pathway

Disinhibition of spinal regulation of nociception transmission

Increase decreasing inhibition of spinal nociception

Question 15

What is are the indications for tramadol?

Answer 15

Moderate pain (less effective for severe pain)

Avoiding the adverse effects of morphine and fentanyl

Question 16

Where and how is morphine metabolised?

Answer 16

Liver

Conjugation with glucuronic acid

Question 17

What are some contradictions to morphine use?

Answer 17

At high risk with respiratory depression - COPD, OSA

CNS - Low conscious state

CVS - relatively hypotensive

Renal impairment - morphine and metabolites will accumulate

Hepatic impairment

Elderly (relative)

Question 18

How is fentanyl administered and dosed?

Answer 18

IV - 100ug/2ml or 500ug/10ml ampoules

Transdermal - 12, 25, 50, 75, 100 ug/hour

Intranasal

Lozenges 200-1200ug

IM

SC

Question 19

What are the drawbacks of codeine?

Answer 19

Genetic variation in the ability to metabolise (CYP 2D6) it into the active form therefore efficacy

• Slow and ultrafast metabolisers

Addictive

GI side effects

Question 20

What are some adverse affects of morphine?

Answer 20

N/V

Constipation

Reduced conscious state

Respiratory depression

Urinary retention

Addiction

Tolerance

Hypotension and bradycardia

Allergy

Question 21

What is the mechanism of action of oxycodone?

Answer 21

Is a semi-synthetic pure opioid agonist

Question 22

What are some indications for oxycodone?

Answer 22

Moderate to severe acute and chronic pain

Question 23

How is oxycodone administered? What are the names of some of the variants?

Answer 23

Oral - Rapid (Endone and oxynorm)

• Slow release (Oxycontine)
• In combination with naxolone (Targin)

Suppository - Proladone

IV - rarely used in Aus