Pharmacologic Treatment of Post-Herpetic Neuralgia (PHN)

Recommendations Tricyclic antidepressants, anti-convulsants, opioids, and topical lidocaine patches are effective and should be used in the treatment of postherpetic neuralgia (Level A evidence) Both gabapentin and the lidocaine patch are approved by the US FDA for the treatment of PHN and are associated with minimal side-effects, some consider these two agents to be first-line treatments for PHN.

Tricyclic Anti-Depressants (TCA) Central and peripheral anticholinergic effects as well as sedative effects. Block the active reuptake of norepinephrine and serotonin Moderate to excellent pain relief Amitriptyline, Nortriptyline, Despiramine, Maprotiline Lots of side effects

Analgesics Opioids Capsaicin Cream Short-acting analgesics provide acute relief of pain Long-acting agents, such as controlled release morphine and oxycodone, can be used for an extended duration of pain relief.  Capsaicin Cream Depletes and prevents reaccumulation of substance P in peripheral sensory neurons that may render skin and joints insensitive to pain. ADE: Intolerable burning pain

Corticosteroids Anti-inflammatory properties Short-term corticosteroid use can be utilized to reduce the severity of pain and improve quality of life in the acute phase Long-term use of corticosteroids is not recommended as they can facilitate bone loss and impair the host immune system, factors particularly of concern in the elderly.

Anti-Viral Agents Shorten the clinical course Prevent complications and the development of latency and/or subsequent recurrences, Decrease transmission, and eliminate established latency. Famciclovir

Anesthetics Stabilize the neuronal membrane so the neuron is less permeable to ions. Prevents the initiation and transmission of nerve impulses, thereby producing the local anesthetic action. Topical 5% Lidocaine Patch Provide relief of PHN for approximately 12 hours after application Side-effects are mild and include local skin reactions such as erythema

Anti-Convulsants Manage severe muscle spasms and provide sedation in neuralgia. They have central effects on pain modulation. Gabapentin Second-generation anticonvulsant Shown to significantly reduce the duration of PHN. Good safety profile, especially among older patients. Side-effects include somnolence, dizziness, and gait disturbances such as ataxia.

Summary: Treatment Categories for PHN (From AAN) Group 1 Medium to high efficacy Good strength of evidence Low level of side effects Gabapentin Lidocaine patch Oxycodone or morphine, controlled release Pregabalin TCA Group 2 Lower efficacy Limited strength of evidence Side effect concerns Aspirin (cream/ointment) Topical capsaicin Intrathecal Methylprednisolone* Intrathecal Methyprednisolone  potential for chemical meningitis and arachnoiditis Intrathecal Lidocaine  risk of hypotension & respiratory depression These injections are given in a hospital setting