COX Inhibitors (Paracetamol and NSAIDs)
Paracetamol (acetaminophen) is a safe and effective first-line analgesic, often used with other agents to enhance pain relief. It has minimal gastrointestinal or renal side effects when used appropriately but should be used cautiously in patients with liver disease or chronic alcohol use. NSAIDs (e.g., ibuprofen, naproxen, diclofenac, celecoxib) inhibit cyclooxygenase (COX) enzymes, reducing inflammation and peripheral sensitisation. They can significantly improve pain control but should be used with caution in patients with renal impairment, peptic ulcer disease, cardiovascular risk, or those on anticoagulants. COX-2–selective agents or short courses may be preferred perioperatively to minimise bleeding risk.
Antidepressants (Amitriptyline, Duloxetine)
Certain antidepressants are valuable in the management of neuropathic and chronic pain. Amitriptyline, a tricyclic antidepressant, is effective for nerve-related pain but may cause sedation, dry mouth, or orthostatic hypotension. Duloxetine, a serotonin–noradrenaline reuptake inhibitor (SNRI), is useful for neuropathic pain and fibromyalgia, with added benefits for comorbid anxiety or depression. Both agents should usually be continued perioperatively, with consideration of potential drug interactions and serotonergic effects when combined with opioids or antiemetics.
Anticonvulsants (Gabapentin, Pregabalin, Carbamazepine, Lamotrigine)
These agents reduce neuronal excitability and are widely used in neuropathic and central pain syndromes. Gabapentin and pregabalin are common choices and may reduce opioid requirements postoperatively. Carbamazepine is effective for trigeminal neuralgia but requires monitoring for hepatic and haematological toxicity. Lamotrigine can be used for central pain or migraine-associated neuropathy. These medications may cause sedation or dizziness and should be dose-adjusted in renal impairment. Abrupt cessation should be avoided.
Opioids (Codeine, Tramadol, Tapentadol, Morphine, Oxycodone, Buprenorphine, Methadone)
Opioids are potent analgesics for moderate to severe pain but carry risks of sedation, respiratory depression, constipation, nausea, and dependence. Codeine and tramadol are weak opioids, with tramadol also acting via serotonergic mechanisms. Tapentadol combines µ-opioid agonism with noradrenaline reuptake inhibition, providing effective analgesia with fewer gastrointestinal effects. Morphine and oxycodone remain mainstays for acute pain, while buprenorphine and methadone are used in chronic or substitution settings. Methadone’s NMDA antagonism offers benefit in neuropathic pain but requires specialist supervision. Perioperative plans should focus on minimising opioid exposure and maintaining chronic therapy safely.
Infusions (Lignocaine and Ketamine)
Intravenous lignocaine and ketamine infusions are valuable in patients with complex or refractory pain, especially with opioid tolerance or central sensitisation. Lignocaine provides analgesic and anti-inflammatory benefits through sodium channel blockade and may reduce postoperative pain and ileus. Ketamine, via NMDA receptor antagonism, reduces central sensitisation and opioid-induced hyperalgesia, offering strong analgesia and opioid-sparing effects. Both agents require specialist administration and close monitoring due to potential cardiovascular or neuropsychiatric effects.
Medical Cannabis (CBD and THC Preparations)
Medical cannabis preparations containing cannabidiol (CBD) and/or tetrahydrocannabinol (THC) are increasingly used for chronic and neuropathic pain. CBD provides anxiolytic and anti-inflammatory effects without psychoactive activity, whereas THC contributes analgesic and muscle-relaxant benefits but may cause sedation or cognitive impairment. Formulations vary (oils, capsules, vapour), and dosing requires careful titration. Patients should inform clinicians before any procedure, as THC may interact with sedatives, anaesthetics, and opioids. Continuation or temporary cessation should be discussed with the prescribing doctor before surgery.