Paracetamol toxicity

Objectives

To be able to do a risk assessment of a paracetamol poisoning
- Consider variables which may affect the risk assessment
Understand the limitations of the nomogram
Understand treatment of paracetamol poisoning

Problem 1

What is enzyme inhibition & how fast does it occur?
What is enzyme induction & how fast does it occur?

Problem 2

A 37-year-old male is brought in following an overdose of paracetamol and temazepam.
He was found by his sister at 9:00 am with empty packets of paracetamol and temazepam. He has taken up to 60 x 500 mg of paracetamol and 25 x 10 mg temazepam sometime the previous day. He is a known chronic alcoholic with a long history of depression. His current medications are citalopram (Cipramil) 20 mg mane and ranitidine (Zantac) 300 mg nocte.
The patient is a slightly wasted 70 kg male who is drowsy with some non-localised abdominal pain. On admission at 10:00 am, his liver function tests are normal but his INR is 1.5. His paracetamol concentration is 420 mmol/L. Four hours later his paracetamol concentration is 275 mmol/L.

What factors can help determine the potential risk of toxicity in this overdose on admission?
What information does the second paracetamol level give and how is this calculated?
What are some of the limitations that may exist in interpreting the levels?
What is the appropriate treatment for this patient initially and over the first 24 hours?

Problem 3

A 45 kg 17-year-old girl ingests 10 x 500 mg of paracetamol 8 hours before and then a further 10 x 500 mg 3 hours before presentation, which she washed down with 5 wineglasses of cask moselle.
She appears well and is cooperative. A physical examination reveals the smell of cheap wine but is otherwise normal.
The paracetamol level at presentation is 505 mmol/L

How would you interpret the paracetamol level?
How would you treat her?
What do you estimate her blood alcohol to be?
Does her alcohol ingestion increase her risk of toxicity?

Problem 4

A 15-year-old girl presents 15 hours after 15 grams of paracetamol. Her body weight is 90 kg. On examination she has hepatic tenderness but no hepatomegaly.

How would you treat this patient on arrival?
These are the Investigations on admission
- Paracetamol level on admission 496 mmol/L
- GGTP 145 U/L, SGPT 892 U/L, SGOT 573
- Prothrombin time normal
What would your treatment be and why?
What is her prognosis and what information is useful to determine the prognosis?