Spinal Cord Stimulation Provides Pain Relief with Improved Psychosocial Function: Results from EMP3OWER.

OBJECTIVE: The EMP3OWER™ study evaluated spinal cord stimulation (SCS) safety and efficacy and the associated changes in psychosocial and functional outcomes. METHODS: Upon informed consent and IRB approval, 620 eligible subjects were enrolled prior to SCS trial evaluation and were assessed at baseline, 3, 6 and 12 months post-implant. Patient-reported pain relief (PRP), numerical rating scale (NRS), satisfaction, quality of life (QOL), and pain disability index (PDI) were assessed at all follow-up visits while the pain catastrophizing scale (PCS), short form-36 (SF-36), short form-McGill pain questionnaire version 2 (SF-MPQ-2), and the state-trait anxiety inventory (STAI) were assessed at the 6- and 12-month follow-up visits. Device and/or procedure-related adverse events were also recorded and reported. Subjects reporting a PRP ≥ 50% were considered responders. Repeated measures analysis of variance (RMANOVA) examined the changes across time for all continuous measures. RESULTS: A total of 401 (71%) subjects received a permanent implant. Mean (±SD) patient-reported pain relief was 59.3% (±26.2), 59.2% (±28.9), and 58.2% (±32.0) at 3, 6, and 12 months, respectively. A majority of enrolled subjects were responders at 3 (75.5%), 6 (74.7%), and 12 months (69.7%). RMANOVA revealed a statistically significant change for NRS, PCS, PDI, SF-36, SF-MPQ-2, and STAI scores. At 3 months, the majority of subjects (85.7%) were either very satisfied or satisfied with their device, with similar results at 6 and 12 months. At 3 months, the majority of subjects (73.3%) reported greatly improved or improved QOL with similar results at 6 and 12 months. CONCLUSIONS: Spinal cord stimulation provided pain relief and significant improvement of patient psychological and functional outcome measures.

Additive and antagonistic antinociceptive interactions between magnesium sulfate and ketamine in the rat formalin test.

Because ketamine and magnesium block NMDA receptor activation by distinct mechanisms of action, we hypothesized that in a model of inflammatory pain in rats the combination of ketamine and magnesium might be more effective than ketamine alone. Antinociceptive activity was assessed by the formalin test in male Wistar rats (200-250 g). Animals were injected with 100 µL of 2.5% formalin to the plantar surface of the right hind paw. Data were recorded as the total time spent in pain-related behavior after the injection of formalin or vehicle (0.9% NaCl). Ketamine and magnesium sulfate given separately reduced nocifensive behavior in the second phase of the formalin test in rats. When ketamine was applied after magnesium sulfate, the log dose-response curves for the effects of ketamine and the magnesium sulfate-ketamine combination revealed antagonistic interaction, and about 1.6 (CL 1.2-2.4) fold increment in ketamine dosage. A low dose of magnesium sulfate (5 mg/kg, subcutaneously) administered after ketamine increased the antinociceptive effect of ketamine by a factor of only 1.2 (CL 0.95-1.38), indicating an additive interaction. There was a 1.8-fold reduction in dosage of ketamine when ketamine was administered before rather than after the magnesium sulfate. The present study revealed that both ketamine and magnesium reduced pain-related behavior in the second phase of the formalin test in rats. Ketamine, when administered before or after the magnesium, provided additive or antagonistic antinociceptive interactions, respectively. Whether there will be an additive or antagonistic antinociceptive interaction between ketamine and magnesium depends on the order of drug administration.