What is the appropriate dosing for gabapentin (anticonvulsant) in an 89-year-old male patient with pruritus (itch)?

Gabapentin Dosing for Pruritus in an 89-Year-Old Male

Start gabapentin at 100 mg once daily (or after dialysis if applicable), then titrate slowly based on tolerability and response, with careful attention to renal function given the patient's advanced age. 1

Initial Dosing Strategy

For an 89-year-old patient with pruritus, the approach must be conservative due to age-related renal decline and increased sensitivity to central nervous system effects:

• Start with 100 mg once daily (typically at bedtime to minimize sedation-related falls) 1, 2, 3
• This low starting dose is supported by evidence in elderly patients and those with renal impairment, where gabapentin has been successfully initiated at 100 mg 2, 3, 4
• The FDA label recommends dose adjustment based on creatinine clearance, which is critical in elderly patients who typically have reduced renal function 1

Titration Protocol

Titrate gradually over 1-2 weeks based on clinical response:

• If tolerated after 3-7 days, increase to 100 mg twice daily 5, 2
• Further increases can be made in 100 mg increments every 3-7 days as tolerated 5, 1
• Most patients with pruritus respond to doses between 300-900 mg/day in divided doses 5, 2, 4
• Maximum doses up to 1800 mg/day have been used for pruritus, but elderly patients rarely require or tolerate such high doses 5, 2

Renal Function Considerations

Mandatory dose adjustment based on estimated creatinine clearance (use Cockcroft-Gault equation for this 89-year-old patient):

• CrCl ≥60 mL/min: Standard dosing up to 300 mg three times daily 1
• CrCl 30-59 mL/min: Maximum 700 mg/day in two divided doses (e.g., 300 mg twice daily) 1
• CrCl 15-29 mL/min: Maximum 300 mg once daily 1
• CrCl <15 mL/min: Maximum 100-150 mg once daily 1

The FDA label provides explicit dosing tables that must be followed in elderly patients, as they universally have some degree of renal impairment 1.

Evidence for Efficacy in Pruritus

The evidence supporting gabapentin for pruritus is strongest in uremic pruritus but extends to other causes:

• Uremic pruritus: 85% response rate in chronic kidney disease patients, with median itch severity decreasing from 8/10 to 1/10 2
• A randomized controlled trial showed significant reduction in pruritus scores (from 8.4 to 1.2) in hemodialysis patients 4
• Neuropathic pruritus: Significant improvement demonstrated in notalgia paresthetica 6
• Cholestatic pruritus: Guidelines mention gabapentin as a consideration, though evidence is limited 5
• Generalized pruritus of unknown origin: Recommended as a treatment option by British Association of Dermatologists 5

Practical Dosing Algorithm for This Patient

Week 1:

• 100 mg once daily at bedtime 2, 3
• Assess for dizziness, sedation, confusion 1

Week 2 (if tolerated):

• Increase to 100 mg twice daily 2
• Reassess pruritus severity using visual analog scale 4

Week 3-4 (if inadequate response):

• Increase to 300 mg twice daily (if CrCl permits) 5, 1
• Some patients may need up to 300 mg three times daily, but this requires normal renal function 1, 4

Maintenance:

• Most elderly patients with pruritus respond to 300-600 mg/day total 2, 4
• Continue at lowest effective dose 1

Critical Safety Considerations

Common pitfalls to avoid in elderly patients:

• Do not use standard adult starting doses (300 mg three times daily) in an 89-year-old—this will cause excessive sedation and fall risk 5, 1
• Always calculate creatinine clearance—serum creatinine alone is misleading in elderly patients with low muscle mass 1
• Monitor for cognitive impairment and confusion, which are more common in elderly patients 7
• Warn about dizziness and fall risk, particularly during titration 1
• Maximum time between doses should not exceed 12 hours to maintain steady-state levels 1

Alternative if Gabapentin Not Tolerated

If the patient experiences intolerable side effects from gabapentin (occurs in ~37% of patients):

• Switch to pregabalin 25 mg once daily, which has 81% efficacy in gabapentin-intolerant patients 2
• Pregabalin has more straightforward dosing but is Schedule V 5

Context-Specific Recommendations

For hepatic pruritus: Gabapentin should NOT be used as first-line; cholestyramine and rifampicin are preferred 5

For opioid-induced pruritus: Gabapentin is a reasonable option but naltrexone is more effective 5

For elderly skin pruritus: Gabapentin may be beneficial after excluding asteatotic eczema with emollients and topical steroids 5

The key principle for this 89-year-old patient is "start low, go slow" with careful renal dose adjustment and monitoring for central nervous system side effects that are amplified in advanced age 5, 1.