During the acute phase of varicella zoster infection, commencement of an antiviral agent (valaciclovir, acyclovir or famciclovir ) within 72 hours from the onset of infection reduces the severity and incidence of postherpetic neuralgia (PHN).
First line treatment of PHN includes the use of tricyclic antidepressants such as nortriptyline (well tolerated) and amitriptyline (less well tolerated), titrated to clinical effect. Gabapentin (Neurontin) and pregabalin (Lyrica) are also well established first line treatments for PHN. Common side effects of these medications include dizziness and somnolence, peripheral oedema, weight gain, asthenia, headache and dry mouth. Effective doses are 1800- 3600mg/day for gabapentin and 150- 600mg/day for pregabalin. Titration is recommended for both drugs but the titration interval is generally shorter for pregabalin (every 3 days).
Topical lidocaine patches (Versatis) has been established as efficacious for PHN. They are generally safe with low systemic absorption and only local adverse effects (mild skin reactions). Up to four patches per day for a maximum of 12 hours within a 24 hour period may be used to cover the painful area. Titration is not necessary. Lidocaine is particularly useful in the elderly, especially if there are concerns about the potential for central effects.
Topical capsaicin cream may be utilized as a second or third line treatment for PHN. Capsaicin is an agonist of the transient receptor potential vanilloid receptor (TRPV1). After several days of application TRPV1 containing sensory axons are desensitized, which inhibits the transmission of pain. Many applications are generally required and a burning sensation may occur for many days before the analgesic effect occurs.
Tramadol has shown pain reduction in PHN with a daily dose of 275 mg. It is a recommended second-line agent in the management of neuropathic pain with level one evidence.
Opioids have been established as being efficacious in the management of peripheral neuropathic pain, in particular oxycodone, methadone and morphine. Common side effects are constipation, sedation, nausea and dizziness and vomiting.
Currently there is minimal evidence in the management of PHN from a nonpharmacological agent.
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