Postherpetic Neuralgia in Patients With Acute Herpes Zoster
Graeme M. Lipper, MD
Postherpetic neuralgia (PHN) is a painful and often debilitating complication of acute herpes zoster virus infection that is characterized by intense neuropathic pain. Victims typically describe their pain as a relentless stabbing, throbbing, or burning that often keeps them awake at night. The disorder, thought to occur due to inflammatory nerve injury during infection, may last months to years and causes intractable pain and morbidity. Risk factors for developing PHN include older age (> 50 years), worse pain associated with the acute viral infection, extensive cutaneous involvement (eg, widespread blistering), and severe prodromal pain. Acyclovir and its analogues (ie, valacyclovir, famciclovir) speed the resolution of herpetic skin lesions and acute pain while reducing viral shedding. However, it remains unclear whether these antiviral drugs reduce the true incidence or severity of PHN.[2-4] In contrast, the herpes zoster vaccine may decrease the incidence of PHN by up to 66.5%.
Tricyclic antidepressants and the anticonvulsant drug gabapentin may reduce the pain of PHN, but few data exist to support their use during the acute phase of zoster to prevent PHN.[6,7] To address this important question, Lapolla and colleagues conducted an open-label study assessing the incidence of PHN after therapy with both valacyclovir and gabapentin (300 mg/day, titrated up to a maximum dose 1200 mg orally 3 times a day as tolerated). Investigators enrolled 133 patients with acute zoster who had moderate to severe pain (mean age, 64.6 years; 67% women, 82% non-Hispanic whites). All patients received both valacyclovir (1000 mg orally 3 times a day x 7 days) and gabapentin (300 mg/day, titrated upward weekly as tolerated to a maximum dose of 3600 mg divided 3 times a day) at the onset of acute zoster. Gabapentin was discontinued for patients who reported mild to no pain over 1 week.