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Paracetamol Overdose

4 Oct 2023

Tags: Medical Emergencies | Toxicology

Introduction

Paracetamol is one of the most commonly used over-the-counter pain relievers and fever reducers worldwide. While it is generally considered safe when taken as directed, an overdose of paracetamol can have serious and potentially life-threatening consequences.

Prehospital care providers play a crucial role in recognising and managing cases of paracetamol overdose, as early intervention can significantly improve patient outcomes.

Prevalence / Prognosis

Each year, approximately 100,000 individuals seek care at emergency departments in the UK due to paracetamol overdose, with approximately half of them requiring admission for treatment with the antidote acetylcysteine.

In 2021, there were 227 reported fatalities in England and Wales attributed to paracetamol poisoning.

Complications that can lead to excessive paracetamol use is abdominal pain and vomiting with more significant complications including renal impairment and acute liver failure.

Paracetamol Overdose Indication

Paracetamol overdose can be unintentional (medication error) or intentional (self-harm). National Poisons Information Service (NPIS) define paracetamol overdose as one of the following:

  • Acute Overdose (Excessive amounts of paracetamol taken over less than one hour)
  • Staggered Overdose (Excessive amounts of paracetamol take over one hour)
  • Therapeutic excess (Excessive amounts of paracetamol not relating to self-harm)

The recommended dose of paracetamol is 4g (75 mg/kg) in a 24 hour period for an adult.

JRCALC defines a single acute overdose as an ingestion of > 4g (75 mg/kg) in a period of less than an hour.

TOXBASE or National Poisons Information Service along with local guidance should also be used when assessing toxicity.

Special toxic dosage calculations for the following groups should be considered:

Pregnant Patients – Use the pre-pregnancy weight

Patients > 110kg – Use 110kg to calculate toxic dose instead of the patient’s actual weight.

In rare cases, the normal use of paracetamol can result in toxicity

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Risk Factors

There are several risk factors which may increase the likelihood of a paracetamol overdose

Misunderstanding Dosage Instructions
Lack of understanding or misinterpretation of dosage instructions on medication labels can lead to accidental overdoses. This is especially true for individuals who do not read labels carefully or use multiple medications containing paracetamol simultaneously.
Multiple Medication Use
Taking multiple medications that contain paracetamol at the same time can lead to unintentional overdose. Paracetamol is a common ingredient in many over-the-counter and prescription medications, including cold and flu remedies, pain relievers, and prescription painkillers.
Chronic Pain Management
Individuals who use paracetamol for chronic pain management, such as arthritis or back pain, may be at a higher risk of overdose if they exceed the recommended dosage over time.
Intentional Overdose
Some individuals may intentionally overdose on paracetamol in an attempt to self-harm or as a suicide attempt. This is a significant risk factor for severe liver damage and other complications.
Alcohol Abuse
Chronic alcohol abuse or heavy drinking in combination with paracetamol can increase the risk of liver damage, as both alcohol and paracetamol are metabolized by the liver.
Liver Disease
People with pre-existing liver conditions or compromised liver function are more vulnerable to paracetamol overdose complications. They may not be able to metabolize the drug effectively.

Clinical Features / History

In most cases, prehospital professionals will be made aware that an overdose of paracetamol has been taken. If not, there are some clinical signs that may suspect a paracetamol overdose has been taken but present differently depending upon the ingestion method (acute, chronic, staggered) and time from overdose to presentation.

History to take is the ingestion method, combination with other medication and dosage taken. Also important to not length of time paracetamol was taken over and the time last taken.

Early Features (0-12 hours)

  • Generally Asymptomatic
  • Diaphoresis
  • Nasuea/Vomitting
  • Mild Abdominal Pain

Late Features (>12 hours)

  • Jaundice
  • Metabolic Acidosis
  • Coagulopathy – Abnormal bleeding or bruising
  • Altered mental state

Management

If a paracetamol overdose has been confirmed or suspected with one of the following:

above > 75 mg/kg over 1 hour or less

intentional paracetamol overdose

presence of overdose symptoms (jaundice)

transport to hospital is needed for blood test to determine paracetamol concertation. Local guidelines may also include other criteria for transport.

Carry out a DR<C>ABCDE assessment and obtain relevant history.

Activated Charcoal should be given if toxins have been ingested less than one hour or if TOXBASE or the National Poisons Information Service have advised the administration activated charcoal.

Once bloods have been taken in hospital, depending upon paracetamol levels, acetylcysteine may be given with greatest effective if given within eight hours of paracetamol ingestion.

 

Activated Charcoal

Check out more information on Activaed Charcoal

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Activated Charcoal

Key Points

  • The toxic effects of paracetamol are dose-dependent, meaning that the risk of harm increases with the amount ingested.

  • Early symptoms may include nausea, vomiting, pallor, and sweating but most patients tend to be asymptomatic.

  • Prehospital treatment for paracetamol overdose is activated charcoal along with transport to hospital.

  • The antidote for paracetamol overdose is N-acetylcysteine (NAC), which should ideally be administered within the first 8 hours after ingestion.

Bibliography

BMJ (2020). Paracetamol overdose in adults – Symptoms, diagnosis and treatment | BMJ Best Practice. [online] bestpractice.bmj.com. Available at: https://bestpractice.bmj.com/topics/en-gb/3000110

Joint Royal Colleges Ambulance Liaison Committee and Association of Ambulance Chief Executives (2022). JRCALC Clinical Guidelines 2022. Class Professional Publishing

Medicines and Healthcare Products Regulatory Agency (2014). Treating paracetamol overdose with intravenous acetylcysteine: new guidance. [online] GOV.UK. Available at: https://www.gov.uk/drug-safety-update/treating-paracetamol-overdose-with-intravenous-acetylcysteine-new-guidance

Introduction

Paracetamol is one of the most commonly used over-the-counter pain relievers and fever reducers worldwide. While it is generally considered safe when taken as directed, an overdose of paracetamol can have serious and potentially life-threatening consequences.

Prehospital care providers play a crucial role in recognising and managing cases of paracetamol overdose, as early intervention can significantly improve patient outcomes.

Prevalence / Prognosis

Each year, approximately 100,000 individuals seek care at emergency departments in the UK due to paracetamol overdose, with approximately half of them requiring admission for treatment with the antidote acetylcysteine.

In 2021, there were 227 reported fatalities in England and Wales attributed to paracetamol poisoning.

Complications that can lead to excessive paracetamol use is abdominal pain and vomiting with more significant complications including renal impairment and acute liver failure.

Paracetamol Overdose Indication

Paracetamol overdose can be unintentional (medication error) or intentional (self-harm). National Poisons Information Service (NPIS) define paracetamol overdose as one of the following:

  • Acute Overdose (Excessive amounts of paracetamol taken over less than one hour)
  • Staggered Overdose (Excessive amounts of paracetamol take over one hour)
  • Therapeutic excess (Excessive amounts of paracetamol not relating to self-harm)

The recommended dose of paracetamol is 4g (75 mg/kg) in a 24 hour period for an adult.

JRCALC defines a single acute overdose as an ingestion of > 4g (75 mg/kg) in a period of less than an hour.

TOXBASE or National Poisons Information Service along with local guidance should also be used when assessing toxicity.

Special toxic dosage calculations for the following groups should be considered:

Pregnant Patients – Use the pre-pregnancy weight

Patients > 110kg – Use 110kg to calculate toxic dose instead of the patient’s actual weight

In rare cases, the normal use of paracetamol can result in toxicity.

Overdose Indication

There are several risk factors which may increase the likelihood of a paracetamol overdose

Misunderstanding Dosage Instructions

Lack of understanding or misinterpretation of dosage instructions on medication labels can lead to accidental overdoses. This is especially true for individuals who do not read labels carefully or use multiple medications containing paracetamol simultaneously.

Multiple Medication Use
Taking multiple medications that contain paracetamol at the same time can lead to unintentional overdose. Paracetamol is a common ingredient in many over-the-counter and prescription medications, including cold and flu remedies, pain relievers, and prescription painkillers.
Chronic Pain Management

Individuals who use paracetamol for chronic pain management, such as arthritis or back pain, may be at a higher risk of overdose if they exceed the recommended dosage over time.

Intentional Overdose
Some individuals may intentionally overdose on paracetamol in an attempt to self-harm or as a suicide attempt. This is a significant risk factor for severe liver damage and other complications.
Alcohol Abuse
Chronic alcohol abuse or heavy drinking in combination with paracetamol can increase the risk of liver damage, as both alcohol and paracetamol are metabolized by the liver.
Liver Disease
People with pre-existing liver conditions or compromised liver function are more vulnerable to paracetamol overdose complications. They may not be able to metabolize the drug effectively.

Clinical Features / History

In most cases, prehospital professionals will be made aware that an overdose of paracetamol has been taken. If not, there are some clinical signs that may suspect a paracetamol overdose has been taken but present differently depending upon the ingestion method (acute, chronic, staggered) and time from overdose to presentation.

History to take is the ingestion method, combination with other medication and dosage taken. Also important to not length of time paracetamol was taken over and the time last taken.

Early Features (0-12 hours)

  • Generally Asymptomatic
  • Diaphoresis
  • Nasuea/Vomitting
  • Mild Abdominal Pain

Late Features (>12 hours)

  • Jaundice
  • Metabolic Acidosis
  • Coagulopathy – Abnormal bleeding or bruising
  • Altered mental state

Management

If a paracetamol overdose has been confirmed or suspected with one of the following:

above > 75 mg/kg over 1 hour or less

intentional paracetamol overdose

presence of overdose symptoms (jaundice)

transport to hospital is needed for blood test to determine paracetamol concertation. Local guidelines may also include other criteria for transport.

Carry out a DR<C>ABCDE assessment and obtain relevant history.

Activated Charcoal should be given if toxins have been ingested less than one hour or if TOXBASE or the National Poisons Information Service have advised the administration activated charcoal.

Once bloods have been taken in hospital, depending upon paracetamol levels, acetylcysteine may be given with greatest effective if given within eight hours of paracetamol ingestion.

 

Key Points

  • The toxic effects of paracetamol are dose-dependent, meaning that the risk of harm increases with the amount ingested.
  • Early symptoms may include nausea, vomiting, pallor, and sweating but most patients tend to be asymptomatic.
  • Prehospital treatment for paracetamol overdose is activated charcoal along with transport to hospital.
  • The antidote for paracetamol overdose is N-acetylcysteine (NAC), which should ideally be administered within the first 8 hours after ingestion.

Bibliography

BMJ (2020). Paracetamol overdose in adults – Symptoms, diagnosis and treatment | BMJ Best Practice. [online] bestpractice.bmj.com. Available at: https://bestpractice.bmj.com/topics/en-gb/3000110

Joint Royal Colleges Ambulance Liaison Committee and Association of Ambulance Chief Executives (2022). JRCALC Clinical Guidelines 2022. Class Professional Publishing

Medicines and Healthcare Products Regulatory Agency (2014). Treating paracetamol overdose with intravenous acetylcysteine: new guidance. [online] GOV.UK. Available at: https://www.gov.uk/drug-safety-update/treating-paracetamol-overdose-with-intravenous-acetylcysteine-new-guidance

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