Pregabalin Rapidly Relieves Neuropathic Pain in Spinal Cord Injury

Alice Goodman

May 15, 2013

New Orleans, Louisiana — A post hoc analysis of 2 large, randomized, placebo-controlled phase 3 studies shows that pregabalin (Lyrica, Pfizer Inc) improves pain associated with spinal cord injury (SCI) within 1 to 2 days after treatment initiation.

Pregabalin was recently approved by the US Food and Drug Administration (FDA) for the treatment of neuropathic pain associated with SCI on the basis of pivotal studies showing effectiveness. The drug is now FDA-approved for 5 conditions: SCI, diabetic peripheral neuropathy, postherpetic neuralgia, fibromyalgia, and partial-onset seizures in adults who require at least 1 antiepileptic medication per day.

"Nonopioids such as tricyclic antidepressants [TCAs] and serotonin-norepinephrine reuptake inhibitors [SNRIs] take a few weeks to relieve pain in SCI patients. Opioids work faster," stated lead author Bruce Parsons, MD, Pfizer Inc, New York City.

"Pregabalin is a nonopioid and is the only medically approved option for treatment of pain associated with spinal cord injury," he said. "In this study, even in patients with neuropathic pain associated with spinal cord injury for an average of 10 years’ duration, we saw onset of pain relief as early as day 1 or 2."

The trials were funded by Pfizer Inc. This post hoc analysis was presented here at the American Pain Society (APS) 32nd Annual Scientific Meeting.

The analysis was based on 2 separate studies of patients with SCI: 1 from Australia and 1 from 10 different countries, including Asia, Europe, South America, and the United States.

The studies enrolled patients with spinal cord involvement from C3 down. All patients had to be able to breathe independently. Dr. Parsons said about half of the study population had complete lesions and the other half had some degree of neural preservation.

In the initial analysis of both trials, pregabalin was statistically superior to placebo at every time point measured. The post hoc analysis looked at time to pain relief in both trials. Pain was based on an 11-point pain scale from 0 to 10, with 10 indicating the worst possible pain. Changes in pain score were analyzed in an intent-to-treat analysis that included a total of 343 patients enrolled in 1 of the 2 trials.

Time to onset of pain relief (TTO) was defined as the first day and the following day that pain scores were significantly better than with placebo. At the study’s end, mean placebo-adjusted pain scores for the pregabalin-treated patients were –1.53 and –0.78 for the 2 trials (P < .001 and P = .003, respectively).

In the Australian trial, TTO for reduction in pain scores occurred on day 1, with a mean improvement in pain score of –1.15 (P < .001); in the second trial, mean improvement in placebo-adjusted pain score was –0.52 on day 2 (P = .007).

"We saw a difference between pregabalin and placebo as early as the end of day 1 in the Australian study and by the end of day 2 in the multinational study," Dr. Parsons said. He noted that the difference between the 2 studies was not unexpected.

The TTO was similar to what has been reported with pregabalin in diabetic peripheral neuropathy and postherpetic neuralgia, although this is based on a historical comparison and not trials comparing TTO in these populations, Dr. Parsons continued.

In an interview with Medscape Medical News, Brett Stacey, MD, professor of anesthesia and perioperative medicine at the University of Oregon Health and Sciences Center in Portland, said that neuropathic pain in patients with SCI is difficult to treat.

"These patients have often had long-standing pain, and nothing seems to work. If you can get positive reinforcement with pain relief in a short time, patients are more likely to adhere to treatment and to have hope. They will feel better and have improved expectations," Dr. Stacey said.

During drug trials, adverse effects usually occur during the first 2 weeks and take time to resolve, he continued. "Some drugs generate side effects before the onset of pain relief. Pregabalin appears to have early-onset analgesia, and patients with SCI appear to be relatively responsive to this drug during the critical period of early initiation."

Dr. Parsons is an employee of Pfizer Inc. Dr. Stacey was not involved in any study of patients with SCI, but he disclosed previous funding from Pfizer for studies in other patient populations.

American Pain Society (APS) 32nd Annual Scientific Meeting. Abstract 339. Presented May 9, 2013.

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