Analgesia: a quick thread
(Mostly for fun)
Paracetamol: old faithful and only surviving analine analgesic. Mild pain and pyrexia. Beware low body weight and pill burden esp in severe pain.

Codeine: mild to moderate pain. Opioid metabolised to active morphine, some will metabolise rapidly via CYD2D6 and at risk of toxicity. Others can metabolise poorly with little benefit. Constipating and can cause rebound headache

Tramadol : delirium in a capsule. Lowers seizure threshold. May have a role in neuropathic pain but better options.

Tapentadol: Tramadol’s slightly better behaved cousin. Good concept of using descending inhibitory pain pathways but complex often equals side-effects. Again better options

NSAIDs: ruthless, no nonsense potent analgesics that are highly effective for many pain types. Side-effects well known and often put people off prescribing. Maintain hydration to reduce impact and give PPI as gastroprotection. COX2 inhibitors worth a second look

Morphine: The gold standard for cancer pain. Always be prepared to reassure patients about the stigma and fears, such as addiction that goes with the name. Caution as renal function falls due to accumulation of neurotoxic metabolites.

Oxycodone: 2nd choice strong opioid for cancer pain after morphine. Often used when toxicity occurs with morphine and pain still an issue. More forgiving in renal failure but still needs caution.

Hydromorphone: Popular in Canada.
Bizarre dosing and variable availability. Actually an excellent analgesic, well tolerated as injection. Unheard of outside palliative care dinner parties and twitter threads

Alfentanil: Toxic on all other opioids or severe renal impairment? Then this might just save the day. Only available in injection. Very quick acting and short half life- often best given as a continuous subcutaneous infusion. Doses in micrograms. Specialist use only

Ketamine: NMDA antagonist potentially useful for severe neuropathic pain and phantom limb pain. Often requires anti-psychotic cover and close monitoring of BP and heart rate. Best left to specialists snd in patient only

Clonazepam: often used for neuropathic pain as an adjunct. Evidence is mainly anecdotal, may be useful for anxiety component to pain. Long half life so somnolence often prolonged.

Amitriptyline: Tricyclic antidepressant with moderate evidence of benefit in some forms of neuropathic pain. Anti-cholinergic side effects often troublesome especially in the elderly.

Gabapentin/Pregabalin: Anti-epileptic drugs which act on calcium channels to reduce neuropathic pain. Titrate slowly to avoid ataxia, somnolence and spaced out sensations. Increase opioid potency when combination used so go slow.

And dont forget the non-pharmacological approaches. Heat, cold, position, environmental adaptations, relaxation, distraction, TENS, interventional service and good old fashioned company

Menthol on Aqueous cream: Apply liberally to localised areas of skin with increased/painful sensitivity to touch (allodynia). Works on peripheral Transient Receptor Potential to reduce calcium flux. Also useful for itch. Do not apply then touch eyes or other delicate areas

Methadone: Another drug with NMDA receptor action. A useful adjunct for some patients with neuropathic pain. The dosing and pharmacology can be complex (also fascinating). Using this drug usually involves much explaining to patient, GP, pharmacist...everyone

Capsaicin creams: Chilli oil derivative applied to areas of neuropathic pain and sensitivity. Depletes substance P and desensitises area. Qutenza 8% patch is “scovilicious” potent and for specialist use only.

TENS/transcutaneous nerve stimulation. Ever stub your wee toe in the middle of the night? Give it a rub and it feel less painful: Gate theory: activate big nerves that carry touch and dull down smaller pain fibres. Superfical electrical currents do the same.. very clever