Pain
-
Randomized Controlled Trial
Botulinum toxin type A reduces capsaicin-evoked pain and neurogenic vasodilatation in human skin.
The effect of Botulinum Toxin type A (BoNT/A) on pain and neurogenic vasodilatation induced by application to the human skin of thermal stimuli and capsaicin was evaluated in a double blind study. A capsaicin cream (0.5 ml of a 0.075%) was applied to the skin of both forearms of eighteen subjects randomly pretreated with either BoNT/A (Botox) or 0.9% saline (NS). Capsaicin was applied to a skin area either inside (protocol A) or adjacent to the BoNT/A treated area (protocol B). ⋯ In Protocol B, capsaicin-induced pain was unchanged, and capsaicin-induced flare/increase in CBF were reduced only in the area treated with BoNT/A, but not in the BoNT/A untreated area. Results indicate that (i) BoNT/A reduces capsaicin-induced pain and neurogenic vasodilatation without affecting the transmission of thermal and thermal-pain modalities; (ii) reduction in capsaicin-induced pain occurs only if capsaicin is administered into the BoNT/A pretreated area; (iii) reduction in neurogenic vasodilatation by BoNT/A does not contribute to its analgesic action. BoNT/A could be tested for the treatment of conditions characterised by neurogenic inflammation and inflammatory pain.
-
Randomized Controlled Trial
Morphine, nortriptyline and their combination vs. placebo in patients with chronic lumbar root pain.
Although lumbar radicular pain is the most common chronic neuropathic pain syndrome, there have been few randomized studies of drug treatments. We compared the efficacy of morphine (15-90 mg), nortriptyline (25-100 mg), their combination, and a benztropine "active placebo" (0.25-1 mg) in patients with chronic sciatica. Each period consisted of 5 weeks of dose escalation, 2 weeks of maintenance at the highest tolerated doses, and 2 weeks of dose tapering. ⋯ Mean doses were: nortriptyline alone, 84+/-24.44 (SD) mg/day; morphine alone, 62+/-29 mg/day; and combination, morphine, 49+/-27 mg/day plus nortriptyline, 55 mg+/-33.18 mg/day. Over half of the study completers reported some adverse effect with morphine, nortriptyline or their combination. Within the limitations of the modest sample size and high dropout rate, these results suggest that nortriptyline, morphine and their combination may have limited effectiveness in the treatment of chronic sciatica.
-
Prior studies evaluating predictors of pain-related outcomes following treatment for sciatica have been limited by methodological problems, including retrospective study design, use of unvalidated outcome measures, and short-term follow-up periods. Despite these limitations, some reports have suggested that symptoms of psychological distress may predict individual differences in pain treatment-related outcomes (e.g., higher levels of depressive and anxious symptomatology are associated with greater pain and disability after treatment). In this study, we sought to determine whether acute symptoms of depression and anxiety were prospectively associated with treatment outcomes over a 3-year follow-up period in surgically treated and non-surgically treated patients with sciatica. ⋯ In most analyses, symptoms of depression and anxiety, both at baseline and at the preceding time point, were significant independent predictors of worse pain and function after controlling for relevant covariates. Collectively, elevated distress appears to be a significant risk factor for reduced treatment benefit (i.e., less improvement in pain and disability) over short and medium-term follow-up periods in patients with sciatica. Future research should determine whether the prospective identification and treatment of patients with high levels of distress (a "yellow flag") is associated with improved treatment outcomes.
-
The level and pattern of daily activities performed by persons with chronic pain are regarded as central determinants of their overall physical, social and emotional functioning. Within the chronic pain literature, various approaches to activity are typically considered, including activity avoidance, "pacing", and particular patterns of high rate activity, sometimes referred to as "overuse" or "activity cycling". Of these, activity avoidance has been most studied, while the others remain poorly understood. ⋯ Groups with the most avoidance and disability reported the lowest levels of acceptance of pain. These data suggest that activity patterns are complex and multidimensional, and that avoidance appears to be the overriding process with regard to daily functioning. Moreover, avoidance patterns may be subtle, sometimes resembling healthy coping, and sometimes presenting along side patterns of high activity.
-
Changes in pain produced by psychological factors (e.g., placebo analgesia) are thought to result from the activity of specific cortical regions. However, subcortical nuclei, including the periaqueductal gray and the rostroventral medulla, also show selective activation when subjects expect pain relief. These brainstem regions send inhibitory projections to the spine and produce diffuse analgesic responses. ⋯ These findings provide direct evidence that the modulation of pain by expectations is mediated by endogenous pain modulatory systems affecting nociceptive signal processing at the earliest stage of the central nervous system. Expectation effects, therefore, depend as much about what takes place in the spine as they do about what takes place in the brain. Furthermore, complete suppression of the analgesic response normally produced by descending inhibition suggests that anti-analgesic expectations can block the efficacy of pharmacologically valid treatments which has important implications for clinical practice.