資料來源：https://www.reuters.com/article/us-health-lyrica-sciatica-trial-idUSKBN16T32Q

Pregabalin, the pain-fighting drug better known by the Pfizer brand name Lyrica, works no better than placebo at relieving the leg pain associated with sciatica, according to results from an Australian study of more than 200 patients.

Volunteers tested after eight weeks of therapy and again at the 52-week mark were just as likely to report improvement whether they received Lyrica or a dummy drug.

The average pain intensity on a zero to 10 scale, where higher numbers mean more pain, was 3.7 with pregabalin and 3.1 with placebo after eight weeks of therapy. The participants started out with pain levels of 6.3 and 6.1, respectively.

After one year, the average leg-pain intensity score was 3.4 with pregabalin and 3.0 with placebo, according to results in the New England Journal of Medicine.

However, pregabalin generated more side effects, with 227 adverse events in that group compared with 124 with placebo. Dizziness was the biggest problem.

"The lack of benefit and increased risk of harm provides a strong case to not use this medicine in patients for sciatica," chief author Dr. Christine Lin of the University of Sydney told Reuters Health in an email.

Pfizer was hoping that if sciatica proved responsive to Lyrica, "this would be a real boon to increase its use," said Dr. Bruce Senter, an assistant professor of orthopedics at Tulane University in New Orleans, who was not involved in the study. "Unfortunately, this study doesn't bear out the usefulness for this."

Although tests of Lyrica from 2003 to 2010 showed that it works for other types of pain, controlled trials conducted during the past five years have tended to show either negative results or minimal effects, write Drs. Nadine Attal of the University of Versailles-Saint Quentin and Michel Barrot of the University of Strasbourg in an accompanying editorial.

There is no definitive therapy for the radiating leg pain of sciatica, which can also spark back pain, reflex problems, weakness and sensory loss. The condition typically goes away in three quarters of patients within three months.

Originally developed as a therapy for epilepsy, most prescriptions for the $5 billion-a-year drug are now for pain relief.

Based on Australian data, perhaps 14 percent of pregabalin prescriptions were for sciatica, Lin estimated.

In the last year or two, Senter told Reuters Health by phone, “more people have been put on it as an as-needed analgesic. This study seems to support that that's not a good use for it. It doesn't seem to work that way."

In the study, volunteers from 47 sites in New South Wales were treated for moderate-to-severe sciatica. Patients who reported severe depression or suicidal thoughts were excluded. Since 2008 the U.S. Food and Drug Administration has required all epilepsy drugs to carry a warning about the risk of suicidal behavior.

All volunteers were advised to remain active and were told their symptoms would probably diminish over time.

In addition to no difference in pain relief, pregabalin produced no significant improvement in disability, back pain intensity, the amount of time absent from work, the likelihood that a patient would use other pain medications or the quality of life on either a physical or mental scale.

"One reason we think that pregabalin does not work for sciatica is that it has different underlying pain mechanisms than other types of nerve pain," Lin said. "Pain mechanisms can be very complex and influenced by a range of pathological and psycho-social factors."

Dizziness was three times more common with pregabalin, seen in four out of 10 patients on the drug. Back pain was nearly twice as common in these patients. None of the drug-related adverse events were considered serious, though.

The researchers saw no increase in suicidal thinking, but the study wasn't designed to detect that as a risk, they caution in the report. “It is important that doctors continue to be cautious with regard to prescribing pregabalin to patients who are susceptible to self-harm,” the study team writes.

SOURCE: New England Journal of Medicine, online March 22, 2017.