What treatments or testing are recommended for a 66-year-old male with idiopathic peripheral neuropathy, recurrent falls, and diminished response to gabapentin (neurontin), with a history of lumbar surgery and herniated disc?

Management of Idiopathic Peripheral Neuropathy with Recurrent Falls and Diminished Gabapentin Response

Switch from gabapentin to duloxetine 60 mg once daily as first-line therapy, add pregabalin if partial response, implement fall prevention strategies including physical therapy and home safety assessment, and pursue targeted diagnostic testing to identify treatable causes of the neuropathy. 1, 2

Immediate Medication Management

Transition to duloxetine as the primary neuropathic pain agent. Gabapentin's diminished effectiveness after 2-3 months suggests tolerance or inadequate dosing, and duloxetine has superior evidence as first-line therapy for peripheral neuropathy. 1, 2

• Start duloxetine 60 mg once daily, with option to increase to 120 mg daily if needed after 2-4 weeks for additional benefit 1, 2
• If duloxetine provides only partial relief after optimization, add pregabalin 150-300 mg/day (divided twice daily) as combination therapy with a different mechanism of action 1
• Alternatively, if duloxetine is contraindicated or not tolerated, pregabalin 300-600 mg/day is an effective first-line alternative with benefits seen as early as week 1 1

Important caveat: Avoid duloxetine if hepatic disease is present; pregabalin and gabapentin may cause peripheral edema and weight gain, which could further impair mobility. 1

Essential Diagnostic Testing

Pursue comprehensive laboratory evaluation to identify treatable causes, as 54-75% of "idiopathic" neuropathy cases have identifiable etiologies. 3, 4

Initial Laboratory Panel:

• Fasting blood glucose and hemoglobin A1c to assess for diabetes mellitus (most common metabolic cause) 2, 5, 3
• Vitamin B12 level (given his transient response to B12 injection, this is particularly relevant) 2, 3, 4
• Thyroid-stimulating hormone to exclude hypothyroidism 2, 3, 4
• Complete blood count and comprehensive metabolic profile including liver and kidney function 3, 4
• Serum protein electrophoresis with immunofixation to screen for monoclonal gammopathies and plasma cell dyscrasias 5, 3
• Erythrocyte sedimentation rate as inflammatory marker 4

Additional Testing Based on Clinical Context:

• Vitamin E, thiamine, folate, and copper levels if malabsorption suspected 5
• Consider hepatitis C and HIV testing if risk factors present 2
• Electrodiagnostic studies (nerve conduction studies and electromyography) if diagnosis remains unclear after initial workup to differentiate axonal versus demyelinating neuropathy 3, 4

Rationale for B12 focus: His transient 2-week improvement following B12 injection suggests possible B12 deficiency contributing to his neuropathy, which is a treatable cause. 2, 5

Fall Prevention Strategy (Critical Priority)

Implement immediate fall prevention measures, as peripheral neuropathy significantly increases fall risk, and this patient has documented recurrent falls. 6, 7

Physical Therapy Referral:

• Prescribe balance training and lower extremity strengthening exercises specifically designed for peripheral neuropathy patients 6, 7
• Teach compensatory strategies: substitute vision for lost proprioception (avoid walking in dark, use nightlights) 7
• Gait training with assistive device (cane or walker) if balance testing shows significant deficits 6, 7
• Upper extremity strengthening to improve ability to catch oneself during falls 7

Home Safety Assessment:

• Arrange facilitated home environmental assessment to identify and modify fall hazards (loose rugs, poor lighting, bathroom grab bars, stair railings) 6
• This is particularly effective in reducing falls post-hospital discharge and applies to high-risk community-dwelling elderly 6

Footwear and Orthotics:

• Recommend proper supportive shoes with non-slip soles and avoid walking barefoot 1, 7
• Consider custom orthotics if foot deformities present from neuropathy 7

Medication Review for Fall Risk:

• Review all medications for fall-increasing agents, particularly psychotropic medications (benzodiazepines, antidepressants, neuroleptics) 6
• Reduce total medication count if taking >4 medications, as polypharmacy independently increases fall risk 6
• Monitor for orthostatic hypotension, especially when starting duloxetine 6

Blood Pressure Episode Management

The elevated blood pressure during balance testing likely represents a physiologic stress response rather than a primary cardiovascular issue, given absence of chest pain, dizziness, or syncope. 6

• No immediate cardiovascular intervention needed based on this isolated episode 6
• However, optimize cardiovascular risk factors (hypertension, hyperlipidemia) as these contribute to neuropathy progression 1, 2
• Assess for orthostatic hypotension at future visits, as autonomic neuropathy can coexist with peripheral neuropathy 6, 2

Sleep Disturbance Consideration

His sleep fragmentation (4-5 awakenings nightly) may worsen pain perception and fall risk, though he reports adequate daytime energy. 6

• Duloxetine may improve sleep quality as a secondary benefit beyond neuropathic pain control 6, 1
• Avoid adding benzodiazepines for sleep due to increased fall risk 6
• If sleep remains problematic after duloxetine initiation, consider low-dose tricyclic antidepressant (amitriptyline 10-25 mg at bedtime), though this carries anticholinergic risks in elderly patients 6, 1

Monitoring and Follow-up Plan

Schedule 4-week follow-up to assess medication response and fall frequency. 1, 2

• Reassess pain using standardized pain scale (0-10 numeric rating) 2
• Document fall frequency and circumstances since intervention 6
• Check for medication side effects: dizziness, somnolence, nausea (duloxetine); edema, weight gain (pregabalin) 1
• Review laboratory results and adjust treatment based on identified deficiencies 2, 3
• If inadequate response after optimizing duloxetine, add pregabalin or switch to alternative first-line agent 1

Additional Non-Pharmacological Interventions

• Loose-fitting cotton socks and shoes to minimize contact discomfort 1
• Cold water foot soaks for temporary pain relief 1
• Regular walking program to improve circulation, but avoid prolonged standing 1
• Consider transcutaneous electrical nerve stimulation (TENS) if refractory to pharmacotherapy 1

Critical pitfall to avoid: Do not continue ineffective gabapentin indefinitely. The evidence shows gabapentin has limited efficacy for many neuropathy types, and duloxetine has superior evidence for both diabetic and idiopathic peripheral neuropathy. 6, 1, 2