Prescribing Notes for Acute Pain

For the management of pain in palliative care, see Prescribing Notes for palliative care. For management of persistent pain, see guidelines on AthenA.

For the management of patients ≥65 years of age having sustained a fragility fracture see guidance here.

N.B. If the patient's pain remains unresolved despite using the treatment guidance below, or local guidelines, then refer to the acute pain team for further advice.

Step 1: Mild pain

Paracetamol

• Is an effective analgesic for mild to moderate pain.
• Improves the effect of other analgesics in the treatment of moderate to severe pain.

N.B. Do not use different routes of administration of paracetamol at the one time.

Paracetamol oral: 1g four times daily (max dose).

Consider dose reduction in patients with low body weight (<50kg), renal / hepatic impairment or glutathione deficiency (chronic malnourishment, chronic alcoholism) to 15mg/kg/dose up to four times daily (max 60mg/kg/day). An example is: paracetamol oral 500mg four times daily. In patients with hepatocellular insufficiency, a dose reduction of the oral preparation should be determined on a case by case basis with senior medical input. N.B. Patients with chronic liver failure may require a further dose adjustment (7.5mg/kg/dose, max 30mg/kg/day).

General Cautions:

• Haematology / ICU patients where pyrexia of sepsis may be masked (‘as required’ prescription may be more appropriate than regular dosing in these patients).
• Hepatic failure (see below under each preparation).
• Renal impairment (see under IV preparation below).
• Low weight (see under IV preparation below).

Paracetamol can be given rectally, however speed of onset is slower than oral administration and absorption is variable. Rectal paracetamol remains useful when other administration routes are not available.

Paracetamol IV

Indication: Short-term treatment of moderate pain following surgery, and for the short-term treatment of fever, when administration by IV route is clinically justified and other routes are not available. If used, review daily and change to oral route as soon as possible. 

Dose: Varies - dependent on weight, renal function and other co-morbidities. See general cautions above, notes and dosing table below to determine dose.

Administration: Infuse ready-made solution over 15 minutes. For doses <1g, remove and discard excess drug / volume then administer required amount from vial.

Important notes for IV paracetamol:

• Low weight (<50kg) or renal impairment (CrCl <30ml/minute) reduce dose using the table below.
• Maximum daily dose of paracetamol IV must not exceed 3g per day in patients with:
  • Hepatocellular insufficiency
  • Chronic alcoholism
  • Chronic malnutrition (low reserves of hepatic glutathione)
  • Dehydration
• In overdose, paracetamol IV may possibly be more toxic than the oral route. See www.toxbase.org (password required) for management.

Table 1 - IV Paracetamol dosing table

Step 2: Moderate pain

Weak opioid analgesics for moderate pain

Co-codamol* oral 30/500mg 1 - 2 tablets four times daily (max 8 tablets in 24 hours) or

Codeine oral 30 - 60mg four times daily (max 240mg/day) or

Dihydrocodeine oral 30mg four times daily (max 120mg/day) (may be effective in patients who do not metabolise codeine. N.B. Dihydrocodeine 60mg will provide little additional analgesia but more pronounced side effects) or

Tramadol oral 50 - 100mg four times daily.

General Cautions

• *Co-codamol contains paracetamol. Certain patient groups e.g. older adults may require a dose reduction, see above.
• Tramadol should not be used routinely. In particular it should not be used as breakthrough analgesia when patients are already prescribed Step 2 opioids. Tramadol may cause less constipation than codeine so is preferable for patients where this may be problematic (e.g. following intra-abdominal surgery) and may be useful in patients with neuropathic pain (off-label use). Avoid in patients with epilepsy and those on other medicines which can lower the seizure threshold (e.g. ciprofloxacin). Be aware of the potential for serious interaction when co-prescribing tramadol and antidepressants.
• Where possible co-prescribe a stimulant laxative.
• Do not prescribe two weak opioids in combination.

Step 3: Severe pain

Use strong opioids e.g. morphine. Continue step 2 analgesia where possible plus morphine as required either orally or SC, or give morphine via PCA. Continue regular paracetamol (but not if already on other preparations containing paracetamol).

If pain is likely to persist or worsen consider stopping regular step 2 analgesia, stepping up to regular step 3 analgesia and referring to pain team if appropriate.

Table 2: Morphine oral - seek senior medical review if >6 doses are used in 24 hours or ≥3 doses used in a 4 hour period with little or no clinical benefit.

See local protocols for IV, SC and PCA administration of morphine.

General notes on morphine

Oral Morphine:

• Reduce morphine dose in the frail, elderly, those with low body weight and those with renal or hepatic impairment.
• Morphine has active metabolites so use alternative opioids in patients with poor renal or hepatic function. Seek advice from clinical pharmacist, senior medical staff or acute pain team. 
• Adding paracetamol and/or an NSAID can reduce opioid dose requirements and enhance analgesic effect of morphine.
• Oral route if available is the route of choice. Titrate dose of morphine to response, monitor closely for over sedation and life-threatening respiratory depression. For further information refer to Reversal of Opioid-induced Respiratory Depression.
• Co-prescribe laxatives (see Management of Constipation).
• Observe for evidence of opioid toxicity. See below for guidance notes.
• Patients with a history of post-operative nausea and vomiting (PONV) or who are at high risk may particularly benefit from prophylactic antiemetics (see Management of PONV).
• Other opioids - contact local acute pain team or pharmacy for further information on other opioids.

Parenteral morphine:

• Use IV only to initiate analgesia in an acute situation, or as PCA (refer to local protocols). It should not be used as breakthrough analgesia and patients must be closely monitored during and after administration for over sedation and respiratory depression.
• Consider oral morphine when parenteral morphine is discontinued.
• For subcutaneous morphine (acute, pre- or post-operative pain) refer to local protocols.

IV to oral morphine equivalence

• Flowchart Opioid Conversion Chart

• See flowchart above for information on opioid equivalence for acute pain patients including IV to oral morphine. Note: SC/IV dose is the same.
• If in doubt / unsure regarding opioid equivalence please refer to local pain team for advice.

Opioid toxicity (seek advice)

• Signs include:
  • Increased drowsiness / sedation
  • Vivid dreams / hallucinations / delirium
  • Muscle twitching / myoclonus jerking
  • Abnormal skin sensitivity to touch
  • Respiratory depression
• Treatment - reduce opioid by 1/3, ensure patient is well hydrated; review and re-titrate the analgesia. Consider adjuvant therapies and/or alternative Opioids. For naloxone guidance in other circumstances, see Reversal of Opioid-induced Respiratory Depression.
• Caution - in renal and hepatic impairment seek dosing advice from your clinical pharmacist or senior member of medical staff.

Adjuvant (in acute pain): NSAIDs (Non-Steroidal Anti-Inflammatory Drugs)

• Ibuprofen oral 400mg - 600mg three times daily (Rarely will 800mg three times daily be required as there is very little additional benefit but an increase in gastrointestinal and cardiovascular side effects) or
• Naproxen oral 250 - 500mg twice daily

The patient's individual risk factors, including any history of cardiovascular disease should be taken into account. Adding NSAIDs can be beneficial and may reduce opioid requirements. They can be used at any step of the analgesic ladder.

Cautions with NSAIDs:

• Age ≥65 years.
• If patients are at risk of gastrointestinal mucosal damage (elderly, previous ulcer history, dyspepsia, serious co-morbidities also on concomitant medicines known to increase GI adverse effects including aspirin, anticoagulants, SSRIs and corticosteroids) but still need NSAIDs, prescribe gastric protection with a proton pump inhibitor:
  • omeprazole oral 20mg daily or
  • lansoprazole oral 15mg - 30mg daily.
• Consider the patient's overall condition and concomitant medication e.g. hypovolaemia, hypotension, heart failure, other nephrotoxic medication.
• Mild renal impairment or hepatic impairment.
• Lifestyle factors – alcohol consumption and cigarette smoking, possibly contribute to risk.
• NSAIDs may be associated with a small increased risk of thrombotic events, particularly when used in high doses and for long-term treatment. Use the lowest effective dose for the shortest period possible.

Avoid NSAIDs:

• In patients with bleeding or past history of upper GI ulceration, aspirin-sensitive asthma, moderate to severe renal impairment.
• In severe heart failure.
• In severe hepatic impairment.