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Phantom Limb Pain — FRCA Final MCQ

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ModeratePain MedicinePhantom Limb PainFRCA Final

A 68-year-old man has persistent phantom limb pain 6 months after a below-knee amputation. He describes burning and shooting pain perceived in the absent foot, rated 7/10. An adherent 8-week trial of gabapentin, titrated to his maximum tolerated dose of 600 mg three times daily, has produced no meaningful benefit. At a non-specialist medication review, gabapentin is to be tapered while referral for multidisciplinary pain management is arranged. Which replacement pharmacological treatment is most appropriate?

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Correct answer: D — Oral amitriptyline 10 mg at night, titrated according to response

Phantom limb pain has neuropathic features. NICE recommends that ineffective initial treatment with gabapentin be replaced by one of the other first-line drugs; amitriptyline is therefore the best option listed. In a patient older than 65 years, 10 mg at night is an appropriate cautious starting dose, followed by titration and monitoring for sedation, anticholinergic effects, postural hypotension and cardiac adverse effects. Amitriptyline enhances descending inhibitory pathways by inhibiting noradrenaline and serotonin reuptake and also has ion-channel effects relevant to neuropathic pain. NICE supports switching rather than assuming that long-term gabapentin–amitriptyline combination therapy is required. Morphine should not be initiated routinely in non-specialist care. Capsaicin cream is principally an option for localised cutaneous neuropathic pain and stump application does not directly treat pain perceived in the absent foot. Diclofenac is ineffective for the neuropathic mechanism, while oral ketamine requires specialist oversight and is not a routine NICE-recommended replacement.

Reference: National Institute for Health and Care Excellence. Neuropathic pain in adults: pharmacological management in non-specialist settings, CG173, recommendations 1.1.8–1.1.12. Last updated 2020. https://www.nice.org.uk/guidance/CG173/chapter/recommendations