Functional Improvements Related to Neuropathic Pain Relief in SCI Patients

In a new study reported in the Journal of Pain Research, scientists at Pfizer examined the relationship between pain reduction and functional outcomes in patients treated with pregabalin or placebo for neuropathic pain (NeP) resulting from spinal cord injury (SCI).¹

Of the estimated 273,000 people in the United States with SCI, approximately 40% suffer from chronic central NeP. Pain in SCI patients is associated with reduced function and quality of life, and increased disability, unemployment, and depression. Increased levels of NeP specifically have been linked with decreased health status and productivity, and higher levels of socioeconomic burden and health care costs and utilization.

Though a primary focus of SCI management and rehabilitation is improved function, the presence of pain can have a negative impact on these efforts. Previous findings show that SCI patients with the most severe pain levels spent fewer days in rehabilitation and less time in rehabilitation treatment compared with patients with lower pain levels or no pain.

“When pain is present, a core element of SCI management is pain reduction to a level that the patient considers acceptable, as complete relief is rarely possible,” wrote the authors of the new study. Various medications are used to treat NeP in SCI, such as  antidepressants, antiepileptic drugs, opioids, and intrathecal drugs, though studies have been based on small samples and short-term treatment.

Pregabalin (by Pfizer) is the only medication that has received approval from the Food and Drug Administration for treatment of SCI-associated NeP, based on 2 clinical trials showing its greater efficacy in reducing pain vs placebo.^3,4 Clinically significant pain reduction was observed in a greater number of patients taking pregabalin, and results of those trials also suggest pregabalin-related functional improvements.

Because previous findings have shown consistent associations between higher pain levels and greater interference with patients’ daily activities, it would seem that NeP relief would result in improvements in functioning. In a post hoc analysis of data from the 2 pregabalin trials, authors of the current study sought to examine the link between changes in pain and functioning in adult SCI patients given either pregabalin (n=181) or placebo (n=172) for treatment of NeP. The studies used flexible-dosage pregabalin (150–600 mg/d) or a placebo taken twice per day for 12 weeks.

While the findings indicate functional improvements with increased pain reduction regardless of treatment condition, pregabalin was associated with shifts toward greater pain relief and improved function compared to placebo. A loess curve “confirmed the trend toward greater functional improvement with increasing pain relief, with a greater slope observed for pregabalin compared with placebo at pain improvement ≥30%,” the authors reported.

The most consistent effects were observed in the domain of sleep, with trends toward greater sleep improvements at higher levels of pain relief associated with pregabalin. This effect may be especially relevant for SCI patients, in whom sleep problems are common, and “many sedative hypnotics that may be used to treat these problems, such as benzodiazepines, are prone to tolerance and dependence,” note the authors.

References

1. Sadosky A, Parsons BEmir B, Nieshoff EC. Pain relief and functional improvement in patients with neuropathic pain associated with spinal cord injury: an exploratory analysis of pregabalin clinical trial. J Pain Res. 2016; 9: 405–416.

2. Siddall PJ, Cousins MJ, Otte A, Griesing T, Chambers R, Murphy TK. Pregabalin in central neuropathic pain associated with spinal cord injury. A placebo-controlled trial. Neurology. 2006; 67(10):1792–1800.

3. Cardenas DD, Nieshoff EC, Suda K, et al. A randomized trial of pregabalin in patients with neuropathic pain due to spinal cord injury. Neurology. 2013; 80(6):533–539