Indication. Neuropathic pain refractory to other therapy.
Action-Probably by neuronal membrane stabilisation.
Drugs-Mexiletine is the preferred drug; flecainide was associated with an increased risk of sudden death in post-myocardial infarction patients. Mexiletine is commenced at a dose of 150 mg/d and increased by the same amount each few days up to a maximum of 750 mg/d. The medication should be taken with food. The side effects include nausea, sedation and tremor. Mexiletine must be given with particular care to patients with ischaemic heart disease or cardiac arrhythmias.
Ketamine-Ketamine, a dissociative anaesthetic used for short surgical procedures, can relieve unresponsive neuropathic pain. It acts as a NMDA receptor antagonist. It is given in subanaesthetic doses by subcutaneous infusion: 0.1-0.5 mg/kg/h and titrated against effect.
Antibiotics-The pain of cellulitis, mucositis and fungating tumours is often compounded by secondary infection. The use of appropriate antibiotic or antifungal agents can improve pain control.