What are the treatment options for postherpetic neuralgia (PHN) or long-term shingles pain?

Treatment Options for Postherpetic Neuralgia

First-line treatments for postherpetic neuralgia should include tricyclic antidepressants, gabapentin, pregabalin, or topical agents like lidocaine patches and capsaicin, with gabapentin being the most well-supported option based on efficacy and tolerability. 1, 2

First-Line Pharmacological Options

Gabapentin

• Start with 300 mg on day 1,600 mg on day 2 (300 mg twice daily), and 900 mg on day 3 (300 mg three times daily), then titrate up to 1800-3600 mg/day as needed for pain relief 1, 2
• FDA-approved for PHN with demonstrated efficacy in randomized controlled trials (NNT = 4.39) 2, 3
• Clinical studies showed efficacy across doses from 1800-3600 mg/day, with no additional benefit demonstrated above 1800 mg/day 2
• Common side effects include dizziness, somnolence, and peripheral edema 2, 4

Tricyclic Antidepressants (TCAs)

• Excellent efficacy with NNT of 2.64, making them highly effective first-line options 3, 1
• Nortriptyline is preferred over amitriptyline due to better tolerability with equivalent analgesic benefit 1, 5
• Start at low doses (10-25 mg) at bedtime and gradually titrate upward based on response and tolerability 1

Topical Agents

• Lidocaine 5% patches provide excellent efficacy (NNT = 2) with minimal systemic absorption, making them particularly suitable for elderly patients or those with comorbidities 3, 1
• Capsaicin (available as 8% patch or 0.075% cream) shows good efficacy (NNT = 3.26) and can provide pain relief for up to 12 weeks 3, 1
• Apply lidocaine 4% for 60 minutes before capsaicin application to mitigate application site pain 1

Second-Line Treatment Options

Pregabalin

• Consider if patients have inadequate response to gabapentin (NNT = 4.93) 3, 1, 6
• Start at 75 mg at bedtime with gradual weekly increase to maximum 600 mg daily in divided doses 3, 6
• FDA-approved for PHN with demonstrated efficacy in multiple randomized controlled trials 6
• Common side effects similar to gabapentin: dizziness, somnolence, dry mouth, and peripheral edema 3, 6

Tramadol

• Shows efficacy with NNT of 4.76 3, 1
• Start at 50 mg once or twice daily with gradual increase to maximum 400 mg daily 3
• Potential for dependence limits it as a second-line agent 3

Third-Line Treatment Options

Opioid Analgesics

• Should not be prescribed as first-line agents for long-term management of PHN 3
• Consider only for patients who do not respond to first-line therapies and report moderate to severe pain 3
• When appropriate, a combination of morphine and gabapentin should be considered for possible additive effects and lower individual doses 3, 1
• Certain opioids (oxycodone, extended-release morphine, methadone) show efficacy (NNT = 2.67) 3

Other Medications

• Serotonin-norepinephrine reuptake inhibitors (SNRIs) like duloxetine may be considered if gabapentin provides inadequate response 3, 1
• Mexiletine (sodium channel blocker) can be used as a third-line treatment at doses of 225-675 mg/day 3

Special Considerations

Elderly Patients

• Start with lower doses and titrate more slowly 1
• Topical treatments are particularly valuable due to minimal systemic effects 1
• Monitor for side effects such as somnolence, dizziness, and mental clouding with gabapentinoids 1

Renal Impairment

• Dosage adjustment for gabapentin required in patients with creatinine clearance <60 mL/min 2
• For creatinine clearance 30-59 mL/min: 400-1400 mg/day in divided doses 2
• For creatinine clearance 15-29 mL/min: 200-700 mg/day in divided doses 2

Treatment Pitfalls and Caveats

• Lamotrigine is not recommended for PHN due to lack of convincing evidence of efficacy and risk of lamotrigine-associated rash 1
• Combination therapy may be more effective when single agents provide inadequate relief 1, 7
• PHN can be very disabling and significantly reduce quality of life, with treatment characterized by high failure rates, so aggressive management is warranted 8
• The incidence of PHN is likely to increase with greater longevity and increasing numbers of immunocompromised patients 5
• Response to therapy is generally inhomogeneous - some patients experience long-term pain control with monotherapy while others are extraordinarily refractory to all measures 9