Paracetamol Quiz

What is the correct regime for standard strength NAC?

• 200mg/kg NAC over 4 hours followed by 100mg/kg over 16 hours

• 150mg/kg over 15 minutes, then 50mg/kg over 4 hours, then 100mg/kg over 16 hours

• 200mg/kg NAC over 4 hours followed by 200mg/kg over 16 hours

• 100mg/kg NAC over 4 hours followed by 200mg/kg over 16 hours

• 24M, 80kg​

• Agent/dose: paracetamol IR 500mg x 40​

• Time: 1.5hrs​

• Clinical features: asymptomatic, normal vital signs and examination

• Check LFTs and APAP at 4 hours—NAC as per nomogram 

• Start NAC, check LFTs and APAP at 4 hours

• Offer activated charcoal, check APAP + LFTs at 4hrs—NAC as per nomogram 

• Offer activated charcoal, Check APAP at 4 hours—NAC as per nomogram 

Answer explanation

When to offer activated charcoal?

IR >10g but <2 hours

IR >30g or 500mg/kg (ie massive OD) that is <4 hours

SR <4 hours

SR can be up to 24 hours depending on dose/bloods

• 24M, 80kg​

• Agent/dose: paracetamol IR 500mg x 40​

• Time: 3.5hrs​

• Clinical features: asymptomatic, normal vital signs and examination

• Medically clear and refer to psych

• Start NAC, check LFTs and APAP at 4 hours 

• Offer activated charcoal, check APAP + LFTs at 4hrs—NAC as per nomogram

• Check APAP + LFTs at 4 hours—NAC as per nomogram

Answer explanation

• 24M, 80kg​

• Agent/dose: paracetamol IR 500mg x 40​

• Time: 10hrs​

• Clinical features: asymptomatic, normal vital signs and examination

• Start NAC, check FBE, EUC, LFTs, coags, VBG, paracetamol level

• Start NAC, check LFTs and paracetamol level

• Offer activated charcoal, check paracetamol level + LFT—NAC as per nomogram

• Check paracetamol level + LFT—NAC as per nomogram

Answer explanation

Unless ALT/AST are >1000, you do not need to check coags/VBG/FBC.

Paracetamol is a weak anticoagulant in overdose and you often see a mildly raised INR early on--This is not clinically helpful.

• 24M, 80kg​

• Agent/dose: paracetamol IR 500mg x 40​

• Time: 28hrs​

• Clinical features: epigastric pain and nausea, normal vital signs and examination

• Start NAC, Check FBE, EUC, LFTs, coags, VBG, paracetamol level 

• Start NAC, check LFTs and paracetamol level

• Offer activated charcoal, check paracetamol level + LFTs—NAC as per nomogram

• Check paracetamol level + LFTs; It is too late for NAC or activated charcoal.

Answer explanation

If patient in remote setting (ie bloods have to be transported)--You would do the full screen

Easy to add on INR/VBG/UEC if LFTs derranged.

• 24M, 80kg​

• Agent/dose: paracetamol IR 500mg x 40​

• Time: 28hrs​

• Clinical features: epigastric pain and nausea, normal vital signs and examination
  
  Bloods show APAP 30mg/L and ALT 78

• Medically clear patient

• Continue NAC infusion and send to EMU, repeat LFTs and APAP level 2 hours before end of infusion

• Commence double-strength NAC and refer to medics, repeat LFTs and APAP level 2 hours before end of infusion

• Continue NAC infusion and refer to medics, repeat LFTs and APAP level 2 hours before end of infusion

Answer explanation

Continue NAC if APAP >10mg/L and/or ALT is >50 U/L

Patient expected to develop liver injury which will progress over next 3 days

• 24M, 80kg​

• Agent/dose: paracetamol IR 500mg x 40​

• Time: between 6 and 12hrs ago​

• Clinical features: asymptomatic, normal vital signs and examination

• Check paracetamol level + LFT, NAC as per 6hr level on nomogram

• Check paracetamol level + LFT, NAC as per 12hr level on nomogram

• Start NAC, check paracetamol level + LFT, stop NAC if under 9hr level and ALT <50

• Start NAC, check paracetamol level + LFT, stop NAC if under 12hr level and ALT <50

Answer explanation

Time Anchoring: Always assume paracetamol was taken at the earliest possible time (ie worst case scenario).

For all other overdoses, assume patient took at the latest possible time (and therefore they are going to get worse before they get better)

• 24M, 80kg​

• Agent/dose: paracetamol IR 500mg x 40, alcohol​

• Time: unknown​

• Clinical features: intoxicated, normal vital signs and examination

• Check FBE, EUC, LFTs, coags, VBG, paracetamol level—Start NAC if ALT >50 or paracetamol >20mg/L

• Start NAC, check LFTs and paracetamol level, stop only if ALT <50 and  paracetamol <10mg/L

• Offer activated charcoal, start NAC and complete full course; Check LFT and paracetamol level at the end

• Check paracetamol level on arrival and in four hours; Start NAC if either level >50mg/L

Answer explanation

Acute ETOH ingestion is actually protective for acute APAP OD! (Chronic ETOH is bad)

Cytochrome P450 2E1 is involved in ETOH metabolism as well as production of NAPQI (ie competitive inhibition)

• 24M, 80kg​

• Agent/dose: paracetamol IR 500mg x 200​

• Time: 3 hours​

• Clinical features: GCS 8/15, normal vital signs

• Start NAC, check FBE, EUC, LFTs, coags, VBG, paracetamol level

• Start NAC, check LFTs and paracetamol level 

• Intubate, give activated charcoal through NGT, start NAC, check FBE, EUC, LFTs, coags, VBG, check paracetamol level at 4hrs to guide strength of NAC

• Intubate, give activated charcoal through NGT, check FBE, EUC, LFTs, coags, VBG, check paracetamol level at 4hrs and give NAC as per nomogram

Answer explanation

• 24M, 80kg​

• Agent/dose: paracetamol IR 2g q2h for 48hrs for dental pain​

• Clinical features: nausea, dental and epigastric pain, normal vital signs and examination

• Check FBE, EUC, LFTs, coags, VBG, paracetamol level and plot on nomogram 

• Check paracetamol level + LFTs and plot on nomogram (48 hours)

• Check FBE, EUC, LFTs, paracetamol level, start NAC and stop only if ALT <50 and paracetamol <20mg/L (<132micromol/L)

• Check LFTs, paracetamol level, start NAC only if ALT >50U/L or paracetamol >20mg/L (>132micromol/L)

Answer explanation

For RTSI (repeated supratherapeutic ingestion), NAC is indicated if:

• initial serum paracetamol concentration is >20 mg/L (132 micromol/L)
  

• initial serum ALT concentration is >50 U/L
  

• patient is symptomatic and investigation results will be delayed by more than 2 hours after presentation.