The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial
Ethnic differences in diffuse noxious inhibitory controls.
Substantial evidence indicates that the experience of both clinical and experimental pain differs among ethnic groups. Specifically, African Americans generally report higher levels of clinical pain and greater sensitivity to experimentally induced pain; however, little research has examined the origins of these differences. Differences in central pain-inhibitory mechanisms may contribute to this disparity. Diffuse noxious inhibitory controls (DNIC), or counterirritation, is a phenomenon thought to reflect descending inhibition of pain signals. The current study assessed DNIC in 57 healthy young adults from 2 different ethnic groups: African Americans and non-Hispanic whites. Repeated assessments of the nociceptive flexion reflex (NFR) as well as ratings of electrical pain were obtained before, during, and after an ischemic arm pain procedure (as well as a sham procedure). The DNIC condition (ie, ischemic arm pain) produced substantial reductions in pain ratings as well as electrophysiologic measures of the NFR for all participants when compared with the sham condition (P < .001). The DNIC condition produced significantly greater reductions in verbal pain ratings among non-Hispanic whites when compared with African Americans (P = .02), whereas ethnic groups showed comparable reductions in NFR. The findings of this study suggest differences in endogenous pain inhibition between African Americans and non-Hispanic whites and that additional research to determine the mechanisms underlying these effects is warranted. ⋯ This study adds to the growing literature examining ethnic differences in experimental pain perception. Our data suggest that these variations may be influenced by differences in descending inhibition.
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Randomized Controlled Trial
Massage reduces pain perception and hyperalgesia in experimental muscle pain: a randomized, controlled trial.
Massage is a common conservative intervention used to treat myalgia. Although subjective reports have supported the premise that massage decreases pain, few studies have systematically investigated the dose response characteristics of massage relative to a control group. The purpose of this study was to perform a double-blinded, randomized controlled trial of the effects of massage on mechanical hyperalgesia (pressure pain thresholds, PPT) and perceived pain using delayed onset muscle soreness (DOMS) as an endogenous model of myalgia. Participants were randomly assigned to a no-treatment control, superficial touch, or deep-tissue massage group. Eccentric wrist extension exercises were performed at visit 1 to induce DOMS 48 hours later at visit 2. Pain, assessed using visual analog scales (VAS), and PPTs were measured at baseline, after exercise, before treatment, and after treatment. Deep massage decreased pain (48.4% DOMS reversal) during muscle stretch. Mechanical hyperalgesia was reduced (27.5% reversal) after both the deep massage and superficial touch groups relative to control (increased hyperalgesia by 38.4%). Resting pain did not vary between treatment groups. ⋯ This randomized, controlled trial suggests that massage is capable of reducing myalgia symptoms by approximately 25% to 50%, varying with assessment technique. Thus, potential analgesia may depend on the pain assessment used. This information may assist clinicians in determining conservative treatment options for patients with myalgia.
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Randomized Controlled Trial
Hypoalgesic effect of the transcutaneous electrical nerve stimulation following inguinal herniorrhaphy: a randomized, controlled trial.
We investigated the effect of transcutaneous electrical nerve stimulation (TENS) for inguinal herniorrhaphy postoperative pain control in a prospective, randomized, double-blinded, placebo-controlled study. Forty patients undergoing unilateral inguinal herniorrhaphy with an epidural anesthetic technique were randomly allocated to receive either active TENS or placebo TENS. Postoperative pain was evaluated using a standard 10-point numeric rating scale (NRS). Analgesic requirements were also recorded. TENS (100 Hz, strong but comfortable sensory intensity) was applied for 30 minutes through 4 electrodes placed around the incision twice, 2 and 4 hours after surgery. Pain was assessed before and after each application of TENS and 8 and 24 hours after surgery. In the group treated with active TENS, pain intensity was significantly lower 2 hours (P = .028), 4 hours (P = .022), 8 hours (P = .006), and 24 hours (P = .001) after the surgery when compared with the group that received placebo TENS. Active TENS also decreased analgesic requirements in the postoperative period when compared with placebo TENS (P = .001). TENS is thus beneficial for postoperative pain relief after inguinal herniorrhaphy; it has no observable side effects, and the pain-reducing effect continued for at least 24 hours. Consequently, the routine use of TENS after inguinal herniorrhaphy is recommended. ⋯ This study presents the hypoalgesic effect of high-frequency TENS for postoperative pain after inguinal herniorrhaphy. This may reinforce findings from basic science showing an opioid-like effect provided by TENS, given that high-frequency TENS has been shown to activate delta-opioid receptors.
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Randomized Controlled Trial Clinical Trial
A randomized, placebo-controlled, crossover trial of cannabis cigarettes in neuropathic pain.
The Food and Drug Administration (FDA), Substance Abuse and Mental Health Services Administration (SAMHSA), and the National Institute for Drug Abuse (NIDA) report that no sound scientific studies support the medicinal use of cannabis. Despite this lack of scientific validation, many patients routinely use "medical marijuana," and in many cases this use is for pain related to nerve injury. We conducted a double-blinded, placebo-controlled, crossover study evaluating the analgesic efficacy of smoking cannabis for neuropathic pain. Thirty-eight patients with central and peripheral neuropathic pain underwent a standardized procedure for smoking either high-dose (7%), low-dose (3.5%), or placebo cannabis. In addition to the primary outcome of pain intensity, secondary outcome measures included evoked pain using heat-pain threshold, sensitivity to light touch, psychoactive side effects, and neuropsychological performance. A mixed linear model demonstrated an analgesic response to smoking cannabis. No effect on evoked pain was seen. Psychoactive effects were minimal and well-tolerated, with some acute cognitive effects, particularly with memory, at higher doses. ⋯ This study adds to a growing body of evidence that cannabis may be effective at ameliorating neuropathic pain, and may be an alternative for patients who do not respond to, or cannot tolerate, other drugs. However, the use of marijuana as medicine may be limited by its method of administration (smoking) and modest acute cognitive effects, particularly at higher doses.
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Randomized Controlled Trial Multicenter Study Clinical Trial
Efficacy of dronabinol as an adjuvant treatment for chronic pain patients on opioid therapy.
We assessed the efficacy of dronabinol (Marinol capsules; Solvay Pharmaceuticals, Brussels, Belgium), a synthetic Delta(9)-THC (tetrahydrocannabinol), in 30 patients taking opioids for chronic pain to determine its potential analgesic effects as an adjuvant treatment. Phase I of this 2-phase study was a randomized, single-dose, double-blinded, placebo-controlled, crossover trial in which subjects were randomly administered either 10 mg or 20 mg of dronabinol or identical placebo capsules over the course of three, 8-hour visits. Baseline self-report measures, hourly ratings of pain intensity, pain relief, pain bothersomeness, treatment satisfaction, mood, side effects, and blood serum levels were obtained. Phase II was an extended open-label titrated trial of dronabinol as add-on medication to patients on stable doses of opioids. Results of the Phase I study showed that patients who received dronabinol experienced decreased pain intensity and increased satisfaction compared with placebo. No differences in benefit were found between the 20 mg and 10 mg doses. In the Phase II trial, titrated dronabinol contributed to significant relief of pain, reduced pain bothersomeness, and increased satisfaction compared with baseline. The incidence of side effects was dose-related. Overall, the use of dronabinol was found to result in additional analgesia among patients taking opioids for chronic noncancer pain. ⋯ This study examines the effect of adding a cannabinoid to the regimen of patients with chronic pain who report significant pain despite taking stable doses of opioids. The results of our preliminary study suggest that dronabinol, a synthetic THC, may have an additive effect on pain relief.