Acute Administration of Gabapentin Can Prevent Postherpetic Neuralgia

Fran Lowry

February 07, 2011

February 7, 2011 (New Orleans, Louisiana) — Acute administration of gabapentin reduces the incidence of postherpetic neuralgia (PHN), and might even prevent it from developing if administered when the first herpes zoster vesicle appears, according to research presented during a late-breaking abstract session here at the American Academy of Dermatology 69th Annual Meeting.

The US Food and Drug Administration approved gabapentin for the treatment of PHN last week.

"Postherpetic neuralgia is very, very difficult to treat once it's in place. In some cases, it can last for the patient's entire life," Whitney Lapolla, MD, from the Center for Clinical Studies in Houston, Texas, told Medscape Medical News. "We wanted to study something that would be more of a preventive measure than a treatment for PHN, because once it develops, nothing really works very well."

Current available treatments include tricyclic antidepressants, anticonvulsants, and a variety of systemic and topical analgesics, but the result is very poor symptom control, she added.

Several animal studies have suggested that gabapentin is more effective when given acutely than after PHN develops, Dr. Lapolla noted.

"We think that gabapentin prevents neuronal sensitization from occurring, although the mechanism is not completely clear," she said.

In this open-label prospective study, she and her coinvestigators added gabapentin to valacyclovir in 133 patients presenting to their clinic within 72 hours of the appearance of the first herpes zoster vesicle. Patients were followed to see how many complained of PHN at 3, 4, and 6 months.

The patients were 50 years or older (mean age, 64.6 years) and had a self-rated pain level of at least 4 on a 10-point Likert scale, where 0 equals no pain and 10 equals the worst pain imaginable. Of these, 38% presented with moderate pain (4 to 6 on the Likert scale), and 62% presented with severe pain (7 to 10 on the Likert scale).

All patients received valacyclovir 1000 mg 3 times a day plus gabapentin at a starting dose of 300 mg daily.

The dose of gabapentin was titrated up weekly to a maximum of 1200 mg 3 times a day, as tolerable.

"Dizziness can be a problem, so it is important to titrate the dose carefully. The dizziness usually goes away, but . . . [patients who are] dizzy definitely will not want to use it. We prefer to go slow and to titrate up to the maximum tolerated dose," Dr. Lapolla noted.

Patients were seen weekly and then at 3, 4, and 6 months. At each visit, they were assessed for rash healing and pain, and were given several quality of life surveys, including the Short Form 36, a survey of sleep disturbance, and a survey about their use of supplementary analgesics.

At the 4-week mark, if patients reported a pain score of 4 or more, they were continued on gabapentin for another 4 weeks. If their pain was less than 4, they were titrated down. "No patient received gabapentin beyond 8 weeks because we wanted to see what the long-term effects on pain would be," Dr. Lapolla said.

The researchers found that the proportion of patients reporting pain decreased steadily. At 3 months, 20% of patients had pain; at 4 months, 18% had pain; and at 6 months, 9.8% had pain.

These results are superior to those reported in a meta-analysis on the management of PHN, Dr. Lapolla said.

"Our proportion of patients who still had pain at 6 months with this regimen was lower than every single study we found," she said.

"All physicians who have patients with acute shingles should begin gabapentin immediately in addition to the antiviral, because, as we have shown, it is beneficial," she concluded.

Commenting on this study for Medscape Medical News, Richard L. Gallo, MD, PhD, professor and chief of dermatology at the University of California at San Diego, said that the data from this study are encouraging.

"Managing postherpetic neuralgia is a very big problem for clinicians and dermatologists. Her data were, I think, supportive of other studies that suggest that this simultaneous use of gabapentin and an antiviral within the first 72 hours of onset of lesions can be helpful," said Dr. Gallo, who moderated the session. He was not part of the study.

Valacyclovir was provided by GlaxoSmithKline. Dr. Lapolla reports that she has financial relationships with NeurogesX and Inhibitex. Dr. Gallo reports financial relationships with Allergan, Ceregenex, Galderma, Inimex, Intendis, Johnson and Johnson, Novartis, and Skin Epibiotics.

American Academy of Dermatology (AAD) 69th Annual Meeting. Presented February 5, 2011.

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