Toxicology Flashcards
When a patient has paracetamol poisoning and presents within an hour, what treatment may benefit them?
Activated charcoal
What is the difference between single paracetamol overdose and staggered paracetamol overdose?
Single acute overdose is defined as an ingestion of >4 g (or >75 mg/kg) in a period of <1 hour, usually in the context of self-harm. Toxbase.
A staggered overdose is the ingestion of multiple doses of paracetamol over a period of >1 hour, usually with the intention of self-harm
What types of paracetamol overdose are there?
Acute (excessive amounts ingested over a period of less than 1 hr - usually self harm)
staggered (excessive amounts ingested over 1 hr - usually self harm)
Therapeutic excess (excessive amount taken with the intent to treat pain or fever and without self-harm intent)
What are the early symptoms of paracetamol overdose (<12hrs)?
Asymptomatic
Nausea
Vomiting
Mild/moderate abdominal pain
What are the late symptoms of paracetamol overdise (12-36hrs)?
Severe abdominal pain
Metabolic acidosis
Jaundice
AKI
Hepatic encephalopathy
Coma
Coagulopathy
What risk factors can increase risk of paracetamol overdose?
History of self harm, history of frequent or repeated use of medication for pain relief, low body weight, cytochrome P450 inducers (like rifampicin, phenobarbital, phenytoin or primidone) and glutathione deficiency –> pts with low levels of glutathione (due to malnourishment) have a higher risk of liver injury following paracetamol overdose
What does therapeutic excess of paracetamol mean?
Therapeutic excess involves paracetamol being ingested above the licensed daily dose and more than or equal to 75mg/kg in 24 hours. It can involve excessive doses of the same paracetamol product or the inadvertent use of multiple paracetamol-containing products simultaneously.
What IMPORTANT questions do you need to ask if taking a history from a patient who presents with paracetamol overdose?
1.The preparation of the paracetamol ingested: combination, strenght
2. The lenght of time the paracetamol products were ingested over
3. Time of ingestion
What investigations could you do if a pt presents with paracetamol overdose?
Paracetamol concentration*
Liver function tests
INR
Urea and electrolytes
Plasma bicarbonate
Plasma glucose
Full blood count
- Some laboratory analysers may underestimate paracetamol concentration by as much as 40% if the blood test is taken during treatment with acetylcysteine. Always check and follow local laboratory guidelines.
What marker in the liver is usually elevated in liver injury caused by paracetamol overdose?
ALT
What does paracetamol overdose treatment depend on?
The type of overdose (like staggered or acute), time of ingestion and the patient characteristics
How should acetylcysteine be given in staggered paracetamol overdose?
Start acetylcysteine IMMEDIATELY and take blood samples 4 hours after the last ingestion
What can happen if IV acetylcysteine is infused rapidly?
There are a number of adverse effects but a common one is an anaphylactoid reaction (non- IgE mediated mast cell release). If this happens, the infusion is usually stopped and restarted at a slower rate.
Acetylcysteine is now infused over 1 hour (rather than 15 mins) because of this risk.
What is the time range of the effectiveness of acetylcysteine in paracetamol overdose?
Should be given within 8 hrs to be effective
When you are stopping acetylcysteine treatment, what must be done?
Repeat bloods (paracetamol conc,, INR and LFTs) before the end of the treatment. Use advice from TOXBASE
