UK Clinical Pharmacy Association


Issues for surgery

Loss of pain control if omitted.

Inadvertent paracetamol overdose if continued due to risk of multiple paracetamol-containing medicines being administered.

Risk of fatality if weight, renal impairment, and risk of hepatotoxicity are not considered when prescribing intravenous (IV), and potentially oral, paracetamol (see Further Information).

Difficulties with post-operative weaning / deprescribing of opioids if combination analgesic preparations containing paracetamol and an opioid are used.

Advice in the perioperative period

Elective and emergency surgery

Continue if taken regularly and needed prior to surgery (including combination products).

Combination products:

  • Co-codamol – contains paracetamol + codeine
  • Co-dydramol – contains paracetamol + dihydrocodeine
  • Tramacet® – contains paracetamol + tramadol
  • Paracetamol + isometheptene
  • Migraleve® – contains paracetamol + codeine + / - buclizine

Consider checking liver function tests (LFTs) if patient has risk factors for hepatotoxicity (see Further Information).

Consideration should be given to prescribing the components of combination products as separate medicines perioperatively, to facilitate review of their appropriateness and encourage deprescribing.

If dose(s) taken on day of surgery, ensure theatre staff are aware of timing of last dose to avoid inadvertent overdosing.

Interoperative considerations

Before administering IV paracetamol:

  • check if a dose has already been taken in last 6 hours
  • check weight and adjust dose if less than 50kg (see Further Information).

Post-operative advice

If taken regularly, restart post-operatively as soon as next dose is due, otherwise restart when needed.

Check anaesthetic records prior to administering in case of intraoperative administration.

If IV paracetamol is required post-operatively (e.g. due to unreliable oral absorption or swallowing difficulties) it is essential to check the dose, frequency, and cumulative dose in 24 hours is appropriate for patient’s weight, renal function and risk of hepatotoxicity (see Further Information). This should also be reviewed if clinical condition changes.

Combination analgesics such as tablets containing paracetamol with an opioid (e.g. co-codamol) should be avoided post-operatively as the fixed doses do not allow for titration to patient need, or the flexibility required for weaning.

Interactions with common anaesthetic agents

None. However, care should be taken to avoid inadvertent overdose of paracetamol if patient has already received a dose of paracetamol-containing medication in the previous six hours.

Interactions with other common medicines used in the perioperative period


Concomitant use of paracetamol with clavulanic acid (found in co-amoxiclav), doxycycline, flucloxacillin or tigecycline can increase the risk of hepatotoxicity. Whilst single surgical prophylactic doses should not pose a problem, bear this interaction in mind if a patient develops signs of hepatotoxicity with continued post-operative treatment.


The prokinetic action of metoclopramide and domperidone may increase the rate of paracetamol absorption, particularly in those with delayed gastric emptying. However, the total amount absorbed is unchanged and therefore unlikely to be clinically significant. Concurrent use need not be avoided.


When prescribing analgesia care should be taken to avoid duplication of paracetamol-containing medicines, which could lead to unintentional overdose. This risk can be reduced by prescribing individual components, rather than combination products.

Further information

Safe prescribing and administration of IV paracetamol

There is a risk of overdose, hepatotoxicity, and fatality if IV paracetamol is dosed incorrectly. Dose adjustment is required in the following circumstances:

  • patients weighing less than 50kg require both a reduced dose and reduced cumulative dose in 24 hours
  • patients with renal impairment (e.g. creatinine clearance <30ml/min) require an extended minimum dosing interval
  • patients with risk factors for hepatotoxicity (e.g. hepatocellular insufficiency, chronic alcoholism, chronic malnutrition, dehydration) require a reduced cumulative dose in 24 hours

Consult product literature and/or British National Formulary for dosing advice.

Reducing oral paracetamol doses in adults (for IV route see above)

Unlike IV paracetamol, the evidence for oral paracetamol dose reduction is limited. Low body weight appears not to be directly correlated with an increased risk of oral paracetamol toxicity. However, it is an indicator that the patient may have other conditions (e.g. chronic malnutrition, anorexia or high alcohol consumption), which require a reduction in oral paracetamol cumulative dose.

There are case reports of malnourished patients, frail elderly patients, and patients with a history of liver disease developing acute liver failure following administration of oral paracetamol at dose of 4g daily. A reduction of the cumulative dose of oral paracetamol to 3g in 24 hours should be considered for malnourished patients or patients with Child Pugh C cirrhosis, irrespective of weight.

In addition, a reduction in clearance of paracetamol has been associated with increased age and frailty. If a patient has a low body weight, increased age and/or frailty the risks and benefits of oral paracetamol, including the risks of hepatotoxicity and the potential risks of alternative treatments (e.g. Non-Steroidal Anti-inflammatory Drugs [NSAIDs], opioids), should be considered.

If a reduced oral paracetamol dose is prescribed, pain control should be monitored, and alternative management strategies offered if needed. Patients should also be advised of the rationale for the lower dose as this will differ from the dosing advice on over-the counter paracetamol-containing products.


Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press [Accessed on 13th March 2022]

Summary of Product Characteristics – Paracetamol tablets 500mg. Accord Healthcare Limited. Accessed via 13/03/2022 [date of revision of the text December 2020]

Baxter K, Preston CL (eds), Stockley’s Drug Interactions (online) London: Pharmaceutical Press. [Accessed on 16th September 2021]

Summary of Product Characteristics – Paracetamol 10mg/ml Solution for Infusion. Accord-UK Ltd. Accessed via 29/09/2021 [date of revision of the text December 2020]

NHS Leeds Teaching Hospitals NHS Foundation Trust (2020) Reducing oral paracetamol doses in adults. Leeds Teaching Hospitals NHS Foundation Trust. [Accessed on 13th March 2022]