Simple analgesia: aspirin and paracetamol Flashcards
What is the onset of action time for IV paracetamol?
5 minutes
How long after administration is peak effect of IV paracetamol, and how long can the effects last for?
40-60 minutes is peak, and can last up to 6 hours.
Where in the gut is oral paracetamol absorbed?
Well absorbed from the small intestine
What is the bioavailability of oral paracetamol?
63-89% - it is subject to first pass metabolism. Undergoes hepatic metabolism and renal excretion.
What is the volume of distribution of oral paracetamol?
0.9 L/kg
Following a severe paracetamol overdose (true or false):
Paracetamol metabolites are scavenged by glutamine
False. The metabolites are usually scavenged by glutathione (not glutamine), but in a severe overdose this scavenging mechanism is rapidly overwhelmed.
Following a severe paracetamol overdose (true or false):
The initial clinical features provide a reliable guide to the severity of the poisoning
False. The initial clinical features of the overdose do not provide a reliable guide to the severity of poisoning, with more serious complications developing after 36 hours.
Following a severe paracetamol overdose (true or false):
Hypothermia can occur
Severe complications of paracetamol overdose include:
-Acute haemolytic anaemia
-Hypothermia
-Hypoglycaemia
-Metabolic acidosis
-Delerium
-Acute hepatic failure (AHF).
Following a severe paracetamol overdose (true or false):
Acute haemolytic anaemia is a recognised complication
True
Severe complications of paracetamol overdose include:
-Acute haemolytic anaemia
-Hypothermia
-Hypoglycaemia
-Metabolic acidosis
-Delerium
-Acute hepatic failure (AHF).
Which of the following can aspirin be used for?
A. Mild to moderate pain
B. Anti-inflammatory in rheumatoid arthritis
C. Anti-inflammatory in osteo-arthritis
D. Secondary prevention in myocardial ischaemia
E. Prevention of all strokes
F. Deep vein thrombosis prophylaxis
G. Pre-eclampsia
All apart from E. Only prevents TIA/ischaemic stroke.
Aspirin is licensed for patients over 16 years of age. It should not be prescribed to patients below the age of 16 years due to the risk of Reye’s syndrome.
What is the oral bioavailability of aspirin?
70%. It is rapidly hydrolysed by hepatic and intestinal esterases to form salicylate.
Which of the following may be caused by normal doses of aspirin?
A. Myocardial infarction
B. Hyperventilation
C. Reduced clotting time
D. Gastric ulceration and bleeding
E. Reduced blood sugar
D & E. Aspirin causes reduced blood sugar at low doses, but some confusion at high doses. E-lfh says increases blood sugar at high doses, but also says that hypoglycaemia is a potential complication of salicylate toxicity.
In context of aspirin overdose, what salicylate levels are considered mild, moderate and severe toxicity?
Mild: <500 mg/L (3.6 mmol/L)
Moderate: 500-750 mg/L
Severe: >750 mg/L
True or false: aspirin overdose causes thrombocytopenia
False. Associated with hypothrombinaemia and inhibition of platelet aggregation.
True or false: aspirin overdose causes coma
True
True or false: aspirin overdose causes metabolic acidosis
True. Aspirin uncouples oxidative phosphorylation
True or false: aspirin overdose causes jaundice
False
True or false: aspirin overdose causes pulmonary oedema
True. Rare but non-cardiac pulmonary oedema can occur due to increased capillary permeability.
Which of the following aids in the excretion of paracetamol:
A. Raising urinary pH
B. Activated charcoal
C. NAC
D. Repeated IV fluid boluses
None of them.
A. Useful in salicylate excretion, not for paracetamol.
B. Activated charcoal binds to paracetamol to reduce absorption, not excretion. It is most effective if taken within 1 hour of paracetamol ingestion.
C. NAC increases glutathione synthesis, binds to NAPQI, reduces NAPQI back to paracetamol and provides inorganic sulphates for paracetamol conjugation. But does not increase excretion.
E. Supportive treatment, does not affect excretion.
An 80-year-old female is brought into the ED after her carers found her drowsy in her armchair with empty packets of paracetamol next to her which she takes for chronic osteoarthritic pain.
Which of the following factors does not increase her risk of hepatotoxicity?
A. Cigarette smoke
B. Malnutrition
C. Old age
D. Chronic alcoholism
E. Hypertension
A. Incorrect. Smoking is a risk factor for hepatotoxicity in paracetamol overdose.
B. Incorrect. Reduced glutathione stores due to malnutrition lead to build up of NAPQI.
C. Incorrect. Reduced liver function could result in result in quicker saturation of paracetamol metabolism pathways and increased NAPQI concentrations.
D. Incorrect. CYP450 system is induced and could increase the production of NAPQI.
E. Correct. Does not cause increase the risk of hepatotoxity in paracetamol overdose and is the correct response.
One of the mechanisms of actions of paracetamol is:
A. Inhibiting descending serotonergic pathways
B. Activating dopaminergic pathways
C. Inhibiting prostaglandin synthesis
D. Inhibiting MOP and KOP receptors
E. Inhibiting cannabinoid receptors
C. Correct. Irreversible COX enzyme inhibitor.
A. Incorrect. Paracetamol activates descending serotonergic pathways.
B. Incorrect. Not known to target it.
D. Incorrect. These are opioid receptors.
E. Incorrect. Paracetamol activates cannabinoid receptors.
