Analgesia

 

Before prescribing any analgesia consult an up-to-date BNF to ensure appropriate and safe prescribing.

The most common post-operative analgesics used are:


Paracetamol 500mg-1g QDS PO Max dose 4g/24 hours

Ibuprofen 200-400mg TDS - QDS PO Max dose 2.4g/24 hours


These are available as over the counter medications and are particularly useful after minor surgical procedures including simple extractions and biopsies.

Paracetamol is regarded as a very safe analgesic but is hepatotoxic in doses exceeding 4g per day, for this reason it should be used with caution in patients with severe hepatic impairment. It is available in tablet, capsule and suspension formulae.

Ibuprofen is a non-steroidal anti-inflammatory drug (NSAID) but needs to be used with caution in asthmatics as it can trigger an asthma attack. Ibuprofen is acidic and is not recommended in patients with a history of gastric ulcers. It is available in tablet, capsule and suspension formulae.

The dose of ibuprofen can be increased to 600mg-800mg but this should be used with sparingly as it will cause gastric irritation and can lead to ulcer formation. If doses of this magnitude are required other analgesics should be considered.


Other NSAIDS include:

Diclofenac 50mg TDS PO or 75mg BD IM

This is a prescription only medication and is suitable for moderate pain relief.


Combining an NSAID with paracetamol has synergistic effects and can deliver very effective post-operative pain relief.

 

Opiods

The most commonly prescribed opiod based analgesic for mild to moderate pain, is codeine and is available in various preparations.

Codeine is available in 30mg tablets or as co-codamol, a combined formulation with paracetamol. Codeine tablets can be combined with standard paractemaol tablets to have the same analgesic effect as co-codamol.


Codeine phosphate 30-60mg QDS PO Max dose 240mg/24 hours


Co-codamol is available as:

an 8mg dose combined with 500mg paracetamol (8/500) 1-2tabs QDS PO over-the-counter (OTC)

a 30mg dose combined with 500mg paracetamol (30/500) 1-2tabs QDS PO prescription only (POM)

It is thought the 8mg dose has sub-therapeutic effects.


Codeine is very useful for short-term pain relief but is very constipating. Opiod analgesics should be used with caution in patients with impaired respiratory function as they can cause respiratory depression.

Other side effects include:

  • nausea
  • vomiting
  • drowsiness - caution with driving
  • hallucinations
  • euphoria
  • tolerance
  • dependence

 

For patients who have undergone a more complex minor surgical procedure, a combination of co-codamol and diclofenac can provide very effective pain relief without the need for morphine.


Morphine is the most valuable opiod for severe pain relief. It is used as the opiod of choice for pain relief in palliative care. It suffers the same side effects as codeine but frequently causes nausea and vomiting as well as inducing a state of euphoria and mental detatchment. It can be used very effectively with paracetamol and other NSAID's to reduce the dose of morphine required for the same amount of pain relief.


Morphine is a controlled drug; the take-home prescriptions need writing carefully with the amount prescribed written in figures and words, and the total amount prescribed also written in figures and words. It is often usefult to liase with pharmacy if you are unsure as to the protocol as it is more efficient than having the prescription returned unfilled due to prescribing errors. It is recommended to liase with a senior member of the team, the anaesthetists or pain management team prior to commencing, or adjusting, opiod pain relief.


Morphine can be prescribed as an immediate release oral solution (oramorph) and comes in 10mg/5ml and 100mg/5ml formulations.

Oramorph is often prescribed as pain relief for 'breakthrough' pain - that is pain not relieved by other analgesics, particularly in patients who have undergone major surgery or palliative care patients. 5-20mg is the dose commonly prescribed however doses up to 100mg-500mg or higher can be given in certain circumstances.

Oramorph can be used to determine a patient's pain relief requirements - they are allowed as much oramorph every 2-4hours to control their pain. The amount of morphine required is then calculated and used to prescribe the appropriate, equivalent morphine modified-released preparations such as MST or zomorph which release morphine over a 12hour period.


Tramadol 50-100mg QDS Dose > 400mg/24 hours not usually required.

Tramadol has fewer side-effects than morphine but is not as effective as other opioids for post operative analgesia in severe pain.


Dihydrocodeine has an efficacy similar to codeine but is not very effective in postoperative dental pain

Fentanyl is used by IV injection for intra-operative analgesia and can be prescribed as a transdermal patch which is changed every 72hours. Fentanyl is not suitable for the management of acute pain or in a patient whose analgesic requirements are rapidly changing.