Don't let the pox shingle you out

Pregabalin relieves pain of chicken pox virus reactivation

By Brian Hoyle

Yin Chen, a retired accountant thought he was done with the chicken pox virus when he was six years old. Sixty years later, however, a rash flared up and sent him running to his GP. Mr Chen was diagnosed with shingles — a reactivation of the chicken pox virus. And as if getting shingles wasn't bad enough, the persistent virus had yet another nasty trick up its sleeve. Mr Chen's rash went away within weeks, but the pain continued for months. He had trouble sleeping, and became moody and depressed. He was diagnosed with postherpetic neuralgia, which occurs chiefly in older people whose immune systems aren't up to snuff. While the condition usually clears up with time, postherpetic neuralgia can rob sufferers of sleep and make their world a dismal place.

Fortunately, hope might be on the way. A study in the April issue of Pain reports that pregabalin cuts down on the pain and mood swings associated postherpetic neuralgia and makes snoozing a whole lot easier. Unfortunately, the treatment comes with a caveat — it's been tainted by a link with cancer.

"Based on [our] results, pregabalin has substantial promise as a therapy for postherpetic neuralgia and could be a welcome addition to the armamentarium of agents used to treat neuropathic pain syndromes," write the authors.

Dr Rainer Sabatowski of the University of Cologne in Germany and his colleagues selected 238 patients with postherpetic neuralgia for the study. They excluded people who hadn't responded to a related drug (gabapentin). This increased the likelihood that the selected patients would respond positively to pregabalin.

Of the 238 patients, 157 were randomly assigned to receive pregabalin. Eighty-one patients were dosed with 150mg/day and 76 patients got twice this amount. The remaining 81 patients received a placebo. No one knew who was receiving drug or placebo. The researchers were aware that a majority of the participants were taking other medications, mainly analgesics, for pain relief.

Those taking pregabalin faired better than those taking the placebo. These benefits began as early as the first week and continued over the course of the eight-week-long study. Response, defined as a 50% decrease in a pain score from beginning to end of the study, occurred in 26% and 28% of those receiving 150 and 300mg/day of pregabalin, respectively. Only 10% of those in the placebo group were as lucky.

The drug-takers also slept better and felt peppier. Even side effects like dizziness, headache and dry mouth didn't dampen their enthusiasm. And, their good vibrations translated to an improved quality of life, as shown by the standard SF-36 Health Survey.

Dr Sabatowski describes the study's findings as "promising" for sufferers of postherpetic neuralgia. This good news comes on the heels of other studies that have shown pregabalin's benefits in relieving the pain of fibromyalgia and epilepsy. Nonetheless, the drug has been linked to tumour development in mice, a fact that halted a clinical trial in 2001 and may put a spanner in the works of further testing.