Adjuvants

Often neuropathic pain responds to these medications rather than to increasing doses of, for example, opioids which may only cause increasing side-effects without any response in the pain.

Tricyclic anti-depressants

Amitriptyline

Caution: Elderly because of side-effects/caution with other medication e.g. tramadol, SSRI - risk of serotonin sydrome

Action: Increases descending inhibitory signals in the spinal cord (noradrenaline and serotonin re-uptake inhibitor)

Usual Dose

10 - 50mg nocte - "start slow and go slow" because of side-effects (e.g. start at 10mg nocte and increase every 2-3 days)

Advantages

Cheap
Good for pathological pain
Also treats depression, poor sleep

Disadvantages

Anti-cholinergic side effects (e.g. urinary retention, dry mouth, constipation, postural hypotension, ?cardiac arrythmias, glaucoma)
Can cause confusion and sedation
Does not work immediately

HYPERLINK TO NZ FORMULARY

Gabapentin/anti-convulsants

Gabapentin

Caution: Particularly elderly and renal failure because of side-effects

Action: "Membrane stabilisers", probably works by reducing abnormal firing of pain nerves so indicated for neuropathic pain. Exact action of gabapentin unclear.

Usual Dose:

Starting doses can be as low as 100mg OD or 100mg TDS

Titrate up to total 900 - 2700 mg per 24 hours

Seek advice for doses over 600mg TDS

Advantages: