Prescribing and administering intravenous paracetamol safely

Safety concerns

Accidental overdose with intravenous (IV) paracetamol remains a safety risk in children and adults.

Deaths have occurred in adults with low body weight due to incorrect IV paracetamol dosing.

IV paracetamol doses 10 times higher than recommended in children have been reported to the UK National Poisons Information Service (NPIS). Some cases required the use of the antidote acetylcysteine.

Choose IV paracetamol

• When medicines cannot be taken by mouth, such as during surgery or when people are nil by mouth.
• If the person is vomiting or has unreliable oral absorption.
• When swallowing is unsafe, for example in people with neurological conditions or without feeding tube access.
• When rapid pain or fever treatment is needed as it works faster than other routes.

Prescribing

IV paracetamol is commonly used as standard analgesia.

Overdosing is often linked to errors such as:

• incorrect dosing in people weighing less than 10kg
• incorrect dosing in people with liver disease
• confusion between mg and mL
• repeating different formulation doses without interval

Adult dosing

The BNF guides on IV paracetamol dosing in adults including those weighing up to 51kg and over 51kg. Maximum daily doses vary by body weight.

Children’s dosing

The BNFc guides on IV paracetamol dosing in children including neonates from a corrected gestational age of 32 weeks.

Maximum daily doses of IV paracetamol vary by age and body weight.

IV paracetamol is not licensed in pre-term neonates and the BNFc dose for children and neonates weighing less than 10kg is unlicensed.

Check your local children’s dosing guidelines where available. The following are examples.

Neonate at 32 weeks and weighing 2kg

A neonate at 32 weeks corrected gestational age and weighing 2kg, can be prescribed 7.5mg/kg/dose of IV paracetamol given as 15mg every 8 hours.

The maximum daily dose is 22.5mg/kg/day in this age group, given as 3 doses over 24 hours.

Full term neonate and weighing 3kg

A neonate born at full term and weighing 3kg, can be prescribed 10mg/kg/dose of IV paracetamol given as 30mg.

The maximum daily dose is 30mg/kg/day in this age group, given as 3 doses over 24 hours. The minimum interval between doses is 4 to 6 hours.

Extreme body weights

Use appropriate dosing principles for people with extreme body weights and ensure the total 24‑hour paracetamol dose is not exceeded. Always consider age, weight and comorbidities such as liver disease.

Underweight

Use actual body weight when calculating IV paracetamol doses in very low weight children and adults.

Overweight and obese

Use ideal body weight or adjusted ideal body weight when calculating IV paracetamol in overweight and obese children.

Milligrams and millilitres

Confusion between a dose in milliGRAMS (mg) and the amount to give in milliLITERS (mL) has caused accidental overdose and death. This has been seen in infants and neonates where doses 10 times higher than recommended doses have been given.

To reduce this risk, electronic prescribing systems should pre-calculate the dose and display the dose in milligrams and millilitres.

Where electronic prescribing is not fully integrated, provide visual weight-based dose-rounding charts for staff to avoid manual calculation.

Example

A child weighing 15kg requires an IV paracetamol dose of 15mg/kg. The calculated dose is 225milligrams.

Using a 10mg in 1mL strength product, 225milligrams will be a volume of 22.5mL IV paracetamol.

Dosing in liver disease

Reduce the total daily paracetamol dose in people with liver dysfunction, chronic alcoholism, chronic malnutrition or dehydration.

Adults

Prescribe a maximum of 3g per day of paracetamol from all routes to adults over 51kg with risk factors for liver disease.

Children

The maximum dose of IV paracetamol in children with risk factors for liver disease varies by age and body weight.

For example, children weighing between 10kg and 50kg should not receive more than 60mg/kg per day by any combination of routes.

Dosing in kidney dysfunction

Increase the dosing interval to at least 6 hours if the creatinine clearance (CrCl) is 30mL/minute or less.

Some manufacturers advise an 8 hour interval if CrCl is less than 10mL/min. Check the product information.

Pregnancy

No dose adjustment is needed unless there are risk factors for liver toxicity. Use the licensed dose of IV paracetamol.

Paracetamol is the analgesia of choice for mild to moderate pain in pregnancy. See Pain: treatment during pregnancy (SPS page) for further advice.

Breastfeeding

Paracetamol is the analgesia of choice in breastfeeding as only small amounts pass into breast milk. See the SPS article Using paracetamol during breastfeeding (SPS page) for further advice.

Administration

Infuse IV paracetamol over at least 15 minutes with a minimum interval of 4 hours between doses. Increase the interval in kidney dysfunction.

Do not give more than 4 doses of paracetamol in 24 hours, accounting for all formulations and routes.

IV product selection

Look‑alike packaging and different volume sizes increase the risk of selecting the wrong product.

Some products are licensed for specific age groups or weights based on volume to reduce overdose risk.

Consider keeping smaller volume sizes for smaller doses.

Doses 150mg or less

Use a 100mg in 10ml IV paracetamol product or a 500mg in 50mL product.

Use a syringe pump.

Doses 150mg to less than 500mg

Use a 500mg in 50mL IV paracetamol product.

Use a syringe pump.

Doses 500mg to 1g

Use a 1g in 100mL IV paracetamol product.

Giving intermittent intravenous infusions by gravity in adults (SPS page) discusses the circumstances where gravity infusions may be suitable.

Incompatibility with other IV medicines

Switching IV to oral

Oral and IV paracetamol doses are not interchangeable. Review the dose whenever the route changes.

Switch as soon as possible.

Stop the IV paracetamol and give the first oral dose at least 4 hours after the last IV dose. Consider using a longer dosing interval if the person has kidney dysfunction.

Calculate the most suitable oral paracetamol dose using your local guidelines, where available, the BNF dosing guide for adults, or the BNFc dosing guide for children.

Do not exceed 4g of oral paracetamol per day in adults.

The oral paracetamol dosing in children is based on actual body weight and should not exceed more than 3 or 4 doses in a day depending on age.

Switching IV to rectal

Rectal and IV paracetamol doses are not interchangeable. Review the dose whenever the route changes.

There is no IV to rectal paracetamol dose conversion.

Dose rectal paracetamol according to BNF and BNFc guidance based on age, weight and individual factors such as liver function.

Rectal paracetamol licensing

The age range for rectal paracetamol suppositories varies from product to product. Always check the Summary of Product Characteristics (SmPC) for licensed age range and indication.

Product registration varies from General Sales List (GSL), Pharmacy (P) medicines, to Prescription Only Medicine (POM).

Loading dose

Not required when switching from IV paracetamol to rectal paracetamol.

Onset of action

IV paracetamol provides pain relief within 5 to 10 minutes of administration and a peak analgesic effect at 1 hour which lasts about 4 to 6 hours.

Rectal paracetamol reaches peak plasma concentrations after about 2 to 3 hours of administration and has a half-life of about 2 hours in healthy people.

Cutting suppositories

Do not cut suppositories. Adjust the dose of rectal paracetamol according to the strength available.

Monitoring advice

• Check baseline liver function tests before starting IV paracetamol, especially in those at risk of liver disease.
• Repeat liver function tests every 24 hours in people on long term IV paracetamol or at risk of hepatotoxicity.
• Monitor kidney function in people with kidney dysfunction in case dose adjustments are needed.
• Review the total daily paracetamol dose to include all routes and combination products to prevent overdosing.
• Assess pain and temperature frequently to confirm effectiveness and consider a switch to oral therapy.
• Check infusion pump settings and volumes before and during administration to ensure correct dose delivery, especially in children.

Toxicity

Paracetamol toxicity is dose related.

Discuss all suspected IV paracetamol toxicity cases with UK NPIS on 0344 892 0111. Managing IV paracetamol toxicity is different to oral paracetamol.

Risk mitigation

Electronic prescribing

Organisations should review digital prescribing functionality to reduce dosing errors while avoiding alert fatigue. Consider reducing alert fatigue by implementing NHS England’s guide for clinical decision support systems.

Electronic prescribing systems can reduce the risk of common IV paracetamol prescribing errors by:

• setting dose limits to avoid over prescribing or under prescribing
• restricting product prescribing by strength and volume to specific age groups, body weight or clinical areas
• flagging duplicate prescriptions with other formulations
• alerting for high-risk people like children or those with liver disease
• tracking errors and trends to collect data to support Learning from medication safety events (SPS page)
• removing risks from illegible handwriting and missed details such as body weight
• auto calculating doses to prescribe and administer in milligrams and millilitres based on weight

Administration

Organisations should review digital functionality to provide cumulative dose warnings when the maximum safe daily dose is exceeded.

Review and utilise the functionality of Dose Error Reduction Software (DERS) on infusion pumps to prevent inadvertent overdose.

IV product selection

Organisations should review medicines related processes and use guidance in Managing medicines safely in pharmacy (SPS page) and Preventing errors on the medicine journey (SPS page). These aim to minimise the risk of incorrect product selection.

To reduce this risk as an organisation, consider:

• standardising IV paracetamol brands and strengths stocked to reduce confusion
• keeping appropriate volume sizes based on dosing size
• using barcode scanning to confirm the correct product before giving it
• promoting awareness for staff to recognise packaging differences and common errors

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