What is the optimal management for a 93-year-old patient with impaired renal function (GFR 57) and inadequate response to gabapentin (300mg TiD) for neuropathic pain?

Management of Neuropathic Pain in a 93-Year-Old Patient with Impaired Renal Function

For a 93-year-old patient with GFR 57 and inadequate response to gabapentin 300mg TID, switching to pregabalin at a dose of 75mg twice daily is the optimal management strategy. 1, 2, 3

Current Situation Assessment

• The current gabapentin dose (300mg TID = 900mg/day) is at the lower end of the therapeutic range and may be insufficient for adequate pain control 1, 4
• At age 93 with GFR 57, the patient has moderate renal impairment which affects medication clearance and increases risk of adverse effects 5
• Gabapentin is primarily eliminated through renal excretion, making dose adjustments necessary in patients with reduced renal function 6, 7

Treatment Options

Option 1: Increase Gabapentin Dose

• Gabapentin could be titrated to 600mg TID (1800mg/day) with careful monitoring 1, 4
• However, higher doses in elderly patients with renal impairment significantly increase the risk of adverse effects including dizziness, somnolence, and confusion 6, 8
• Gabapentin toxicity in renal impairment can manifest as myoclonus, confusion, and even hearing loss 6, 9

Option 2: Switch to Pregabalin

• Pregabalin has more predictable absorption and linear pharmacokinetics compared to gabapentin 1, 2
• For patients with GFR between 30-60 mL/min, pregabalin dosing should be adjusted 2, 3
• Starting dose of 75mg twice daily (150mg/day) is appropriate for this patient 2, 3
• Can be titrated to 300mg/day based on efficacy and tolerability 3

Recommended Treatment Plan

1. Discontinue gabapentin with gradual taper over at least one week to avoid withdrawal symptoms 1, 2
2. Initiate pregabalin at 75mg twice daily (150mg/day) 2, 3
3. Monitor for efficacy and side effects for 2-3 weeks before considering dose adjustment 1, 2
4. If needed and tolerated, increase to 100mg twice daily (200mg/day), not exceeding 300mg/day in this elderly patient with renal impairment 2, 3

Rationale for Recommendation

• Pregabalin is preferred over higher doses of gabapentin in this patient due to:
  • More predictable pharmacokinetics in renal impairment 1, 2
  • Lower risk of dose-related adverse effects at therapeutic doses 1, 2
  • Better efficacy at lower doses compared to gabapentin 1, 2
  • Twice-daily dosing may improve adherence compared to three times daily gabapentin 2, 3

Monitoring and Precautions

• Monitor for common side effects including dizziness, somnolence, dry mouth, and peripheral edema 2, 3
• Be vigilant for signs of toxicity such as confusion, myoclonus, or altered mental status 6, 8
• Assess pain control using validated pain scales at each follow-up 1, 10
• Avoid concurrent use of other CNS depressants if possible 5, 1

Common Pitfalls to Avoid

• Avoid starting at high doses of pregabalin in elderly patients 1, 2
• Do not abruptly discontinue gabapentin when switching to pregabalin 1, 2
• Avoid exceeding recommended doses for patients with renal impairment 5, 3
• Be aware that coadministration of nephrotoxic drugs (e.g., NSAIDs) should be minimized 5