Paracetamol

Summary of recommendations: paracetamol

Indications and effectiveness

Efficacy is clear in acute situations with an NNT of 3.8 for 50% pain relief with a single 1000mg dose. It is less clear in chronic pain depending on the condition.

• Clinicians should be aware that paracetamol does not significantly improve pain or function in osteoarthritis in short term (three to six months) or intermediate term (more than six months)⁴⁶
• Current guidance notes paracetamol should not be used as sole therapy for chronic backpain^17,18,45 sciatica (lumbar radiculopathy)^18,45 or osteoarthritis⁴⁶ but may be considered in conjunction with NSAIDs
• Evidence showed showed that it has no additional benefit in improving osteoarthritis pain, quality of life or physical function compared with placebo⁴⁷. However, it is recognised that some people cannot use NSAIDS. Therefore it was noted there were some circumstances where it may be used as a sole agent
• There are unlikely to be new large-scale trials with paracetamol. It is widely available over the counter (OTC) and as such individuals can be dismissive of its benefits before trialling. Pragmatically, for longer term pain conditions it may be worth trialling and assessing impact on pain relief and/or function. There are no strong recommendations for regular or ‘as required’ dosing and this should be assessed at individual level of benefit. Similarly, whilst there is no specific evidence to support, it may help minimise opioid load and could be prescribed alongside opioids either in combination or as individual products
• Good Practice Points:
  • In persistent pain a two-to-four-week trial of regular paracetamol dosing three to four times daily can be used to assess efficacy
  • Individuals can determine whether regular use or when required use suits their pain management most
  • Regular use may support reduced use of opioids

Risks and harms

• Paracetamol is generally safe in appropriate doses although adverse reactions such as gastrointestinal (GI) bleeds and decreased renal function have been identified, linked to possible prostacyclin mode of action.⁴⁸ More research is needed
• Standard dosing of a healthy average weight adult in the UK is 500-1000mg every four to six hours (4 grams per 24 hours)
  • Dosing should be reduced in people with low body weight (>33kg to <50kg) and in those over 50 kg with risk factors for hepatotoxicity
  • Risk factors include:
    • excess alcohol consumption
    • concomitant medicines that induce liver enzymes (e.g. carbamazepine, St John’s Wort)
    • those likely to have reduced glutathione levels (eating disorders/cystic fibrosis)
    • the frail and/or elderly - some clinicians prefer to limit dose per administration in the frail elderly over 75 years to 500mg as a single dose and a maximum of 2g daily. Check your local guidance

Individuals should be aware that other medicinal products may contain paracetamol and lead to inadvertent excess dosing e.g. cough and cold preparations. The total daily dose of paracetamol across all products should not exceed 4g.