NEW YORK — The combination of gabapentin with an antiviral and analgesics was more effective than were those drugs without gabapentin for reducing pain in patients with herpes zoster, suggesting that it may prevent postherpetic neuralgia in these patients, said Dr. Stephen Tyring, who presented as-yet-unpublished findings at the American Academy of Dermatology's Academy 2007 meeting.
Dr. Tyring, professor of dermatology, microbiology/molecular genetics, and internal medicine at the University of Texas, Houston, and colleagues enrolled 934 patients with herpes zoster whose pain measured at least a 4 on the Likert Pain Scale.
A control group of 800 patients received valacyclovir for 7 days along with various standard analgesics. An additional 134 patients also received gabapentin in the following regimen: 300 mg nightly for 1 week, followed by 300 mg three times daily for another week, then 600 mg t.i.d. for the following week, followed by yet another higher dosage until the patient complained of side effects (dizziness, drowsiness), at which point the dose was reduced to the highest tolerated dose and maintained until the end of the first month of treatment.
If, at that point, a patient's Likert score had dropped to below 4, the gabapentin was gradually discontinued over 3–4 days and the patient followed for 6 months. If the pain score was 4 or higher at the end of the fourth week, the patient received the highest tolerated dose of gabapentin for another 4 weeks and was then tapered off the drug.
Of those who received gabapentin in addition to valacyclovir and analgesics, only 12 patients (9%) had any pain at 6 months. In marked contrast, 33% of the 800 shingles patients who received valacyclovir and analgesics without gabapentin still had pain after 6 months. These results suggest that gabapentin may induce a neuroimmunomodulation of neuralgia, Dr. Tyring said.
The study was supported by GlaxoSmithKline, which provided the valacyclovir used.
Patients with a pain score of less than 4 were excluded “because the most effective predictor of postherpetic neuralgia, in addition to age, is degree of pain. So if the pain score has not even hit a 4 by the time they present to us with their vesicles, it will probably do no harm, but there's probably no benefit in giving the gabapentin or the pregabalin,” he said, noting that gabapentin is more economical than pregabalin (Lyrica).
'The most effective predictor of postherpetic neuralgia, in addition to age, is degree of pain.' DR. TYRING
ELSEVIER GLOBAL MEDICAL NEWS