What is the preferred treatment between Lyrica (pregabalin) and gabapentin for postherpetic neuralgia?

Gabapentin vs. Pregabalin for Postherpetic Neuralgia

Gabapentin should be considered the first-line oral pharmacological treatment for postherpetic neuralgia (PHN), with pregabalin reserved as a second-line option for patients who have an inadequate response to gabapentin. 1

Efficacy Comparison

• Gabapentin demonstrates significant efficacy for PHN with a number needed to treat (NNT) of 4.39, showing statistically significant improvement in pain scores compared to placebo 2
• Pregabalin has similar efficacy with an NNT of 4.93, also showing statistically significant improvement over placebo 2
• Both medications work through similar mechanisms, binding to voltage-gated calcium channels to reduce the release of excitatory neurotransmitters 3
• FDA approval data confirms efficacy of both medications for PHN, with multiple placebo-controlled trials showing significant pain reduction 4, 5

Dosing and Titration

Gabapentin

• Start at 300 mg on day 1,600 mg on day 2, and 900 mg on day 3, titrating up to 1800-3600 mg/day as needed 1
• Effective doses typically range from 900-3600 mg/day in divided doses 5
• No additional benefit has been demonstrated above 1800 mg/day 1
• A study showed that starting with 600 mg/day (200 mg three times daily) is safe and effective for gabapentin-naive patients with PHN 6

Pregabalin

• Typically started at 25-50 mg/day in elderly patients or those with renal impairment 2
• Effective doses usually range between 150-600 mg/day in two divided doses 2
• Faster titration is possible compared to gabapentin due to more favorable pharmacokinetics 3
• Median time to onset of pain relief is 1.5-3.5 days for pregabalin compared to >4 weeks for placebo 3

Advantages and Disadvantages

Gabapentin

• Advantages:

  • Lower cost as generic medication 1
  • More extensive clinical experience and longer safety record 5
  • Well-established efficacy in multiple trials 7

• Disadvantages:

  • Requires three-times-daily dosing at higher doses 5
  • Non-linear pharmacokinetics requiring careful titration 1
  • Common side effects include dizziness, somnolence, and peripheral edema 7

Pregabalin

• Advantages:

  • Linear pharmacokinetics allowing more predictable dosing 8
  • Twice-daily dosing schedule 4
  • Potentially faster onset of action 3

• Disadvantages:

  • Higher cost (especially brand name) 1
  • Similar side effect profile to gabapentin 8
  • May be excluded as first-line therapy by some insurance formularies 1

Special Populations

• Elderly patients:

  • Start with lower doses of either medication and titrate more slowly 2
  • For gabapentin, consider starting at 100-200 mg/day 2
  • For pregabalin, consider starting at 25-50 mg/day 2

• Renal impairment:

  • Both medications require dose adjustment in renal impairment 4, 5
  • Pregabalin may be preferred in some cases due to simpler pharmacokinetics 4

Treatment Algorithm

1. First-line therapy: Start with gabapentin at 300 mg on day 1,600 mg on day 2, and 900 mg on day 3, titrating to 1800 mg/day as tolerated 1
2. If inadequate response after 4 weeks: Consider increasing gabapentin dose up to 3600 mg/day if tolerated 5
3. If still inadequate response or intolerable side effects: Switch to pregabalin, starting at 150 mg/day divided into two doses, titrating up to 600 mg/day as needed 2
4. For patients with localized pain: Consider adding topical lidocaine patches (NNT = 2) as adjunctive therapy 2
5. For patients with inadequate response to both gabapentinoids: Consider tricyclic antidepressants (NNT = 2.64) or SNRIs 2, 1

Common Pitfalls and Caveats

• Avoid abrupt discontinuation of either medication; taper gradually over at least one week to prevent withdrawal symptoms 4, 5
• Monitor for somnolence, dizziness, and mental clouding, especially in elderly patients 2
• Be aware of potential drug interactions, particularly with CNS depressants 8
• Gabapentin has not shown efficacy for prevention of PHN when given during acute herpes zoster 9
• Both medications may cause weight gain and peripheral edema 8

In conclusion, while both medications are effective for PHN, gabapentin should be considered first-line therapy due to its established efficacy, lower cost, and extensive clinical experience, with pregabalin reserved for patients who have an inadequate response to gabapentin or require a simpler dosing schedule.