Very painful to study

Question 1

Morphine
Moa ?
Other effects?
Onset
Half life

Answer 1

Mu opioid receptor agonist, activating descending inhibitory pathways of the CNS as well as inhibition of the nociceptive afferent neurons of the PNS.
Other = resp depression, vasodilation, slow AV node conduction
Onset = 5mins IV, 10mins IM
Duration = 1-2hrs
Half life = 2 hours

Question 2

Fentanyl;
Moa
Onset 
Half life
Elimination

Answer 2

Mu opioid rector agonist as well as delta and kappa receptors, inhibiting descending pathways
Onset = 3mins
Half life = 2-3hrs
Elimination = hepatic metabolism and renal excretion

Question 3

Does fentanyl have high or low volume of distribution?
Why?
What does this mean for infusions?

Answer 3

High volume of distribution.
Because of High lipid solubility.
When used in infusions if can accumulate in adipose tissue causing a prolonged effect

Question 4

Tramadol;
Moa
Onset 
Half life
Elimination

Answer 4

Mu opioid receptor agonist in addition to serotonin and noradrenaline reuptake inhibitor
Half life = 5-6hrs
Elimination = metabolised by liver excreted by kidney

Question 5

Paracetamol:
Mode of action?
Onset? PO vs IV

Answer 5

It acts as a prostaglandin inhibitor
Oral = 37mins
IV = 8mins

Question 6

How do opioids cause respiratory depression?

Answer 6

By reducing chemoreceptor sensitivity to carbon dioxide

Question 7

What is the mechanism of action of opioids generally?

Answer 7

Cause cell membrane hyperpolarisation by activating inhibitory G-proteins causing potassium efflux, reduced cAMP which inhibits neurotransmitter release

Question 8

What is the mechanism of opioid-induced chest wall rigidity?

Answer 8

Activation of Dopaminergic and GABA pathways in substantia nigra and striatum