Antiviral Drugs May Cut Shingles Pain

Researchers Call for Larger Study to Test the Strategy

Medically Reviewed by Louise Chang, MD on May 08, 2006

May 8, 2006 -- It might be possible to use antiviral drugs to reduce shinglesshingles pain, researchers report.

Dianna Quan, MD, and colleagues studied 15 patients with moderate to severe shingles pain (postherpetic neuralgia). The condition stems from the reactivation of the varicella-zoster virus.

The varicella-zoster virus causes chickenpoxchickenpox. Afterward, it lies dormant in the body's nervous system. If the virus reactivates later in life, it can cause a rash and pain, a condition commonly called shingles since the rash appears in a band-like distribution.

Shingles pain usually resolves within four to six weeks but can last for months and years. "As many as one million Americans are affected," write Quan and colleagues, citing statistics from other researchers.

Quan's study appears online in the Archives of Neurology.

Drug Test

Quan works in the neurology department at the University of Colorado Health Sciences Center in Denver. Participants in her study got a two-pronged antiviral drug plan.

"If chronic pain reflects active infection, then antiviral therapy may help patients with PHN," the researchers write. Post-herpetic neuralgia (PHN) is the medical term used to describe the pain complication from shingles.

A large study could test that theory. But such studies are "time-consuming and expensive," write Quan and colleagues. As a trial run, they studied a small group of patients with shingles pain to see if the antiviral drug strategy held any promise.

Participants were at least 50 years old. They had moderate to severe shingles pain that had lasted for at least three months.

First, the patients rated their shingles pain on a scale of 0-10. A rating of 0 was for no pain; 10 marked the worst possible pain. Participants' average score was 5 when the study started.

Next, the patients received IV doses of the antiviral drug Zovirax (acyclovir) every eight hours for 14 days, followed by oral doses of another antiviral drug, Valtrex (valacyclovir), three times daily for one month.

Participants rated their shingles pain immediately after completing Valtrex treatment, and again a month later.

Shingles Pain Dropped

Eight patients -- 53% -- had their shingles pain scores drop by at least two points after antiviral treatment. The researchers call that decline a "clinically significant reduction in pain."

People sometimes respond favorably to any treatment, so researchers often compare active treatments to sham treatments (placebo). No placebo treatments were tested in Quan's study.

The researchers don't know how the patients would have responded to a placebo. They also can't rule out the possibility that shingles pain improved for reasons unrelated to the antiviral drugs.

However, patients' self-reported improvement in shingles pain probably wouldn't have happened spontaneously. The effect also seems to beat placebo response in other studies, according to the study.

A larger trial of the antiviral drugs is warranted, write Quan and colleagues.

Reported Side Effects

Of the 15 patients who started the study, five left the study early. One patient couldn't tolerate multiple IV catheter insertions. Another had a rise in blood levels of creatinine, which can indicate kidney problems, while taking Zovirax. This returned to normal levels when the medication was stopped.

A third patient developed a respiratory infection which was then complicated by aggravation of a pre-existing condition of atrial fibrillation(heart rhythm irregularities) and elevated liver enzymes while taking the Zovirax. "These events were not likely related to acyclovir," write Quan and colleagues.

Two other patients left the study while taking oral Valtrex. One of them had unexplained difficulty breathing; the other reported feeling nauseous, tired, and ill. "These symptoms disappeared when valacyclovir was stopped," the researchers write.

Show Sources

SOURCES: Quan, D. Archives of Neurology, May 8, 2006; online edition. News release, JAMA/Archives.

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