Opioids Flashcards
What is the mechanism of action of tramadol?
Weak mu receptor partial agonist
Inhibitor of noradrenaline and serotonin reuptake to have anti-nociceptive effects
How long until the onset of analgesia in IV fentanyl?
Minutes
What is the mechanism of action of fentanyl?
Same as morphine
What are the non-analgesic effects of morphine?
Sedation
Anxiolysis
Cough suppression
Reduced gut motility
What is the normal IV dose of morphine?
2.5-5mg
How is tramadol administered and dosed?
Oral - immediate acting - 50 to 100mg
- Slow release - 12hour - 50, 100, 200, 300
- Slow release - 24hours - 100, 200, 300
IV 100mg / 2mg ampule
What are the routes of administration of morphine? Compare their time to peak analgesic effect
Oral - 60 minutes
IM - 30-60 minutes
SC - 50-90 minutes
IV - 20 minutes
Epidural and intrathecal
What are some adverse effects of tramadol?
Seizures
Serotonin syndrome
Others as with morphine but much less severe
What are some indications for codeine?
Mild to moderate pain
Antitussive
Antidiarrhoeal
What are some indications for morphine use?
Moderate to severe pain
Anxiolysis - APO
Adjunct analgesia in general anaesthetic and intubation
Palliative care
What is serotonin syndrome?
A constellation of symptoms associated with excess serotonin due to iatrogenic causes
- Seizures
- Arrhythmias
- Rhabdomyolysis
- DIC
- Acute renal failure
- Respiratory failure
What are some contraindications for tramadol?
Lower the threshold for seizures therefore - epilepsy, those at risk of epilepsy
Other serotonergic drugs - eg SSRIs
Compare fentanyl with morphine
Fentanyl is 100x more potent, 100ug is equivalent to 10mg
More stable affects in the CVS
Faster acting cf to morphine
What is the mechanism of action of morphine?
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
What is are the indications for tramadol?
Moderate pain (less effective for severe pain)
Avoiding the adverse effects of morphine and fentanyl
Where and how is morphine metabolised?
Liver
Conjugation with glucuronic acid
What are some contradictions to morphine use?
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)
How is fentanyl administered and dosed?
IV - 100ug/2ml or 500ug/10ml ampoules
Transdermal - 12, 25, 50, 75, 100 ug/hour
Intranasal
Lozenges 200-1200ug
IM
SC
What are the drawbacks of codeine?
Genetic variation in the ability to metabolise (CYP 2D6) it into the active form therefore efficacy
- Slow and ultrafast metabolisers
Addictive
GI side effects
What are some adverse affects of morphine?
N/V
Constipation
Reduced conscious state
Respiratory depression
Urinary retention
Addiction
Tolerance
Hypotension and bradycardia
Allergy
What is the mechanism of action of oxycodone?
Is a semi-synthetic pure opioid agonist
What are some indications for oxycodone?
Moderate to severe acute and chronic pain
How is oxycodone administered? What are the names of some of the variants?
Oral - Rapid (Endone and oxynorm)
- Slow release (Oxycontine)
- In combination with naxolone (Targin)
Suppository - Proladone
IV - rarely used in Aus
