Gabapentin Plus Valacyclovir Effective for Management of Acute Zoster Pain

Peggy Peck

March 25, 2003

March 25, 2003 (San Francisco) — Results from an open-label pilot trial of gabapentin with valacyclovir given within 72 hours of herpes zoster pain onset suggest that gabapentin (Neurontin) is effective for reducing pain, but the tolerable doses may be much lower than previously reported, according to research presented here Monday at the 61st annual meeting of the American Academy of Dermatology.

Mathijs Brentjens, MD, from the University of Texas Medical Branch in Galveston, told Medscape that earlier studies suggest an effective dose range of 1800 to 3600 mg, but in this study the maximum tolerable dose was 900 mg for more than half of the subjects. "This suggests the need for more study to more accurately determine effective dosing," he said.

Brentjens' coauthor, Gisela Torres, MD, from the University of Texas Medical Branch Center for Clinical Studies in Galveston, pointed out that "this study investigates the use of gabapentin for acute zoster pain rather than late onset pain, and that might be a factor. However, it is useful to note that the patients achieved effective pain management at this lower dose." She said that a larger study could determine if lower doses are equally effective for pain management during acute zoster outbreaks and postherpetic neuralgia (PHN).

The most common dose-limiting adverse effects were dizziness and drowsiness.

A total of 39 patients older than 50 years were enrolled within 72 hours of zoster onset, and all patients had a pain score of least 4 on 0-10 pain index scale. Patients began treatment with valacyclovir 1000 mg orally three times daily for seven days and gabapentin (in sequentially increasing doses for up to 8 weeks beginning at 300 mg). Patients were assessed weekly for six months using the pain index scale, SF-36 general health survey, and a zoster-specific survey.

The maximum tolerable dose was 900 mg or less for 53% of the patients and only 1% tolerated the maximum study dose of 3600 mg. Interestingly, only 18% of patients tolerated 1800 mg "which is the dose reported in PHN studies," said Torres.

Sixty-three percent of the patients continued to receive gabapentin for four weeks and 37% received it for eight weeks.

Brentjens said the average pain score decreased from 7.65 at baseline to 0.85. "Fifteen patients reported they were pain free after 12 weeks," he said. At six months only three of 20 evaluable patients reported zoster pain, two of these had a pain score of 1 and one had a score of 2 on the 0-10 pain index scale.

When poster session discussion cochair, Peter Heald, MD, professor of dermatology at Yale-New Haven Hospital in Connecticut, asked attendees how many were writing prescriptions for Neurontin, about 20% of the group raised their hands. "So, we can see that the use of this drug is already creeping into our practice. That suggests the need for studies such as this," Dr. Heald said. But he added that the paper by Dr. Brentjens and colleagues was significantly flawed because it lacked a control arm. Ideally, he said, a trial should compare gabapentin plus an antiviral to an antiviral alone.

"When measuring pain we just don't learn very much by relying solely on the historical control," he said.

Dr. Brentjens agreed with the criticism and he said that his group is actively seeking support for a larger placebo-controlled study. He noted that this small study received no pharmaceutical company support.

In an interview after the presentation, Drs. Brentjens and Torres said they have applied for funding from both the National Institutes of Health and the Herpes Zoster Foundation.

AAD 61st Annual Meeting: Abstract P38. Presented March 24, 2003.

Reviewed by Gary D. Vogin, MD

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