The journal of pain : official journal of the American Pain Society
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Temporal summation of deep tissue pain has been suggested to be facilitated in chronic musculoskeletal pain syndromes. This study aimed to test whether temporal summation of mechanical induced pressure pain is (1) more pronounced at short (1 second) interstimulus intervals (ISIs) compared with long ISI (30 seconds), (2) more potent than summation elicited by pure skin stimulation, and (3) attenuated in women compared with men. Twelve age-matched men and 12 women were included. A computer-controlled pressure stimulator with a probe surface of 1 cm2 was used to give 10 stimulations to the tibialis anterior, tibia periosteum, and the first web of the hand. Sequential stimulation at pressure pain threshold intensity was applied with different ISIs (1, 3, 5, 10, and 30 seconds). The pain intensity was assessed on a visual analog scale (VAS) after each individual stimulus. The VAS scores after the 10th stimulation with 1-second ISI were increased (P < .05) by 418% +/- 77%, 378% +/- 89%, and 234% +/- 66% compared with the first stimulation for tibia, tibialis anterior, and web, respectively. Temporal summation of pain was observed for all ISIs in tibialis anterior and tibia, eg, 30-second ISI evoked a VAS increase of 192% +/- 71 % (tibia) and 117% +/- 42% (tibialis anterior) compared with the first stimulation. The VAS score after the 10th web stimulation was smaller (P < .05) than that of the 10th tibialis anterior or tibia stimulation. A regression analysis between stimulation number and VAS score showed that the pain intensity increased progressively (1) more for 1-second ISIs compared with longer ISIs (P < .01) and (2) faster in deep tissue compared with skin (P < .01). No gender difference was observed. The temporal summation might be related to both central and peripheral mechanisms. ⋯ Pain originating in deep tissue influences central pain processing systems more than superficial tissue. This might be of importance in patients with musculoskeletal pain.
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Chronic pain patients often report fears that movement will exacerbate their symptoms. The Tampa Scale of Kinesiophobia (TSK) was designed to assess fear of movement. Previous findings with the TSK showed inconsistent factor structures and varied measurement properties. The TSK was completed by a sample of 233 patients with fibromyalgia syndrome who were being evaluated for participation in a rehabilitation program. A principal components analysis initially derived a 5-factor solution. However, the factor structure accounted for less than 50% of the variance, and the internal consistency of the factors was below conventional standards (<0.70). A series of principal components analyses "forcing" different factor structures revealed that the best solution was a single factor solution that contained 4 of the original 17 TSK items, accounting for more than 50% of the variance with adequate internal consistency (alpha =0.71). Inspection of the content of these 4 items, however, suggests that this factor more likely represents catastrophic thinking, rather than fear of movement. Nevertheless, for patients with fibromyalgia syndrome, a 4-item TSK appears to retain the most acceptable factor solution while also maintaining adequate internal consistency. ⋯ Although the TSK is one of the most commonly used measures of fear of movement, the present study using the TSK with a sample of patients with fibromyalgia syndrome suggests that the measurement properties of the TSK are problematic. Recommendations for use of the TSK are provided.
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Persons aged >65 years with pain caused by postherpetic neuralgia (PHN) were recruited via advertisements in 24 US newspapers and were mailed a questionnaire that addressed pain intensity (average, worst, least, current), pain interference (with general activity, mood, relations with other people, sleep, enjoyment of life), and health-related quality of life (using the EuroQoL health measure [EQ-5D] and a global rating scale). Respondents also were asked about their use of medication for shingles pain. A total of 385 persons completed the survey; 61% were >75 years of age. Mean (+/-standard deviation) duration of PHN was 3.3 (+/-4.0) years. Only about one half had taken prescription medication for shingles pain during the prior week; dosages were typically low. Mean average, worst, least, and current pain caused by shingles (0- to 10-point scale) was 4.6 (+/-2.1), 6.0 (+/-2.4), 2.9 (+/-2.3), and 4.0 (+/-2.7), respectively. Mean pain interference with general activity, mood, relations with other people, sleep, and enjoyment of life (0- to 10-point scale) was 3.7 (+/-3.1), 4.3 (+/-2.9), 3.0 (+/-2.8), 3.8 (+/-2.9), and 4.5 (+/-3.1), respectively. The mean EQ-5D health index score was 0.61; respondents rated their overall health as 65.7 (+/-21.1) on a 100-point scale. PHN causes substantial pain, dysfunction, and poor health-related quality of life in older persons, many of whom might be suboptimally treated. ⋯ Many older persons (age >65 years) with PHN experience longstanding, severe, and debilitating pain and poor health-related quality of life; levels of dissatisfaction with treatment are high. Our study highlights the need for improved management of this disease.
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Randomized Controlled Trial Clinical Trial
Adding ultralow-dose naltrexone to oxycodone enhances and prolongs analgesia: a randomized, controlled trial of Oxytrex.
Oxytrex is a novel drug that combines oxycodone with ultralow-dose naltrexone, an opioid antagonist. Ultralow-dose opioid antagonists have been demonstrated to enhance and prolong opiate analgesia and alleviate opioid tolerance and withdrawal in rodents. This 3-week, Phase II clinical trial assessed safety and analgesic efficacy of Oxytrex in patients with moderate to severe pain from osteoarthritis. Patients with a pain score > or =5 received placebo, oxycodone 4 times a day (qid), Oxytrex qid, or Oxytrex twice a day (bid). All active treatment groups received the same total daily dose and dose escalation of oxycodone starting at 10 and ending at 40 mg/day. Importantly, the Oxytrex bid group received a lower daily dose of naltrexone than Oxytrex qid (0.002 vs 0.004 mg/day). Oxytrex bid produced a 39% reduction in pain intensity, which was significantly greater than that of placebo (P < .001), oxycodone qid (P = .006), and Oxytrex qid (P = .003). Oxytrex bid was also superior to placebo in quality of analgesia (P = .002), duration of pain control each day (P = .05), patients' global assessments (P = .04), and the Western Ontario and MacMaster Universities Osteoarthritis Index total score (P = .03). The incidence of side effects was comparable between active treatments. In this Phase II dose-ranging study, Oxytrex bid demonstrated greater pain relief with a more convenient dosing schedule compared to oxycodone qid. ⋯ Preclinical data have shown ultralow-dose opioid antagonists to enhance and prolong opioid analgesia while reducing analgesic tolerance and physical dependence. Recent molecular pharmacology data show a mechanism of action to be the prevention of aberrant G protein coupling by opioid receptors that underlies opioid tolerance and dependence.