Many analgesics are available both over-the-counter and on prescription. Choice of analgesic should be based on type, location and severity of pain. The World Health Organisation (WHO) pain ladder suggests that mild analgesics should be considered first-line and additional medications may be incorporated into the patient’s treatment regimen if pain still remains appropriately severe. The WHO pain ladder can be found here.

The various classes of analgesics work in different ways and some agents may be more beneficial than others in certain scenarios. For example, patients with neuropathic pain may get more effective pain relief from drugs which are not traditionally considered analgesics (e.g., anticonvulsants)

  1. Paracetamol
    • The mechanism of action of paracetamol is poorly understood
    • It is thought that paracetamol inhibits cyclooxygenase, with high selectivity for COX-2
    • Paracetamol has both analgesic and antipyretic activity
    • It is generally well-tolerated and has few side effects
    • Overdose can cause liver damage and, in rare cases, kidney damage
  2. Non-steroidal anti-inflammatory drugs (NSAIDs)
    • Include aspirin, diclofenac, ibuprofen, indometacin, ketoprofen, mefenamic acid, meloxicam, nabumetone, naproxen, piroxicam and tranexamic acid
    • NSAIDs inhibit cyclooxygenase, thereby decreasing prostaglandin production
    • They have both analgesic and anti-inflammatory activity
    • The most common side effects of NSAIDs are gastro-intestinal irritation, dyspepsia, and gastric ulcers. If Ulcers become ruptured the patient may experience significant gastrointestinal bleeding and anaemia
  3. COX-2 selective inhibitors
    • Includes etoricoxib and celecoxib
    • Selectively inhibit cyclooxygenase-2, thereby decreasing prostaglandin production
    • They are as effective as traditional NSAIDs but are associated with less upper-gastrointestinal side effects
    • However, use of COX-2 selective inhibitors can significantly increase risk of adverse cardiovascular events
  4. Opioids
    • Include buprenorphine, codeine, diamorphine, fentanyl, methadone, morphine, oxycodone, pethidine, tramadol etc.
    • Opioids act on opioid receptors
    • They are very effective analgesics but have some troublesome side effects including nausea and vomiting, itching, constipation and drowsiness
    • Excessive opioid dosing can cause opioid toxicity which is associated with respiratory depression, confusion, and seizures
    • There is significant risk of addiction
    • Tolerance may develop after prolonged use, at which point dosage may need to be increased to maintain adequate analgesia
    • Opioid-naive patients should be started on low dose opioids and dose should only be increased if analgesia is insufficient.
    • Analgesic requirements can vary dramatically between individuals and, since opioid tolerance can remain a problem at progressively elevated doses, daily doses should be considered on an individual basis taking into account opioid tolerance, current dose, and analgesia requirements. In essence, there is no ceiling dose for opioids
  5. Other agents
    • Anticonvulsants (like gabapentin, carbamazepine, and pregabalin) and tricyclic antidepressants (like amitriptyline) are often effective in the treatment of neuropathic pain
    • Nefopam is a centrally-acting non-opioid analgesic which may be of benefit if other non-opioids provide insufficient pain relief.
    • Many different topical analgesics are available. Topical NSAIDs can be highly effective at treating localised pain and inflammation whilst minimising gastro-intestinal side effects. Anaesthetics preparations can also be used for local pain relief, such as in the treatment of toothache, mouth ulcers etc.