The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial Clinical Trial
Withdrawal hyperalgesia after acute opioid physical dependence in nonaddicted humans: a preliminary study.
Hyperalgesia has been demonstrated to be a cardinal sign of physical withdrawal from opioids in preclinical models for more than 30 years, although few empirical data exist to support its occurrence in humans. In this preliminary study we used the acute opioid physical dependence (APD) model to test for the presence of hyperalgesia to experimental cold-pressor pain in 4 healthy non-opioid-dependent men via 3 different pretreatment opioid administration protocols previously demonstrated to induce APD (morphine 18 mg/70 kg intramuscular, morphine 10 mg/70 kg intravenous, hydromorphone 2 mg/70 kg intravenous), repeated on 2 separate occasions, and placebo. ⋯ Paired t tests comparing change scores between the opioid pretreatments and placebo showed that pain threshold and tolerance to the cold-pressor uniformly decreased across all APD induction methods, and the effect size was large (approximately 70% of baseline) and reproducible. These findings provide initial support for the existence of opioid-induced hyperalgesia, which has been conceptualized as a coexisting opponent process to opioid-induced analgesia and proposed to be an alternative explanation for the development of analgesic tolerance to opioids.
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Randomized Controlled Trial Multicenter Study Clinical Trial
Long-term intrathecal opioid therapy with a patient-activated, implanted delivery system for the treatment of refractory cancer pain.
The present study evaluated the safety and efficacy of patient-activated delivery of intrathecal morphine sulfate boluses delivered by way of a novel internalized intrathecal delivery system. Patients with refractory cancer pain or uncontrollable side effects were enrolled at 17 US and international sites in this prospective, open-label study. Pain relief, reduction in systemic opioid use, and reduction in opioid-related complications were analyzed both individually and together as a measure of overall success. ⋯ Significant reduction in the opioid complication severity index was demonstrated at all 4 follow-up visits (P <.01). Overall success (>/=50% reduction in numeric analog scale pain, use of systemic opioids, or opioid complication severity index) was reported in 83%, 90%, 85%, and 91% of patients at months 1, 2, 3, and 4, respectively. This study demonstrated that patients with refractory cancer pain or intolerable side effects achieved better analgesia when managed with patient-activated intrathecal delivery of morphine sulfate via an implanted delivery system.
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Randomized Controlled Trial Clinical Trial
Effectiveness of transcutaneous electrical nerve stimulation on postoperative pain with movement.
This study tested the effectiveness of episodic transcutaneous electrical nerve stimulation (TENS) as a supplement to pharmacologic analgesia on pain with movement and at rest after abdominal surgery and evaluated whether its use during walking and vital capacity maneuvers enhances performance of these activities. TENS, with a modulated frequency, intensity as high as the subject could tolerate, and electrodes placed on either side and parallel to the incision, was compared to placebo TENS and pharmacologic analgesia alone (control) by using a crossover design. Self-report of pain intensity, walking function, and vital capacity were assessed on 33 subjects. ⋯ Vital capacity and pain intensity at rest were not significantly different among the 3 treatments. These results suggest TENS reduces pain intensity during walking and deep breathing and increases walking function postoperatively when used as a supplement to pharmacologic analgesia. The lack of effect on pain at rest supports the hypothesis that TENS works through reducing hyperalgesia.
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Randomized Controlled Trial Clinical Trial
A randomized study of the effect of oral lamotrigine and hydromorphone on pain and hyperalgesia following heat/capsaicin sensitization.
In this randomized double-blind placebo-controlled study, the analgesic effect of oral lamotrigine (400 mg) on cutaneous sensitization induced with the heat/capsaicin sensitization model was compared with the effect of oral hydromorphone (8 mg) in healthy volunteers. In a separate session, intravenous remifentanil (0.10 microg.kg(-1).min(-1)) and placebo were administered. This session was used as an additional reference comparator. ⋯ Compared with placebo, both intravenous remifentanil and oral hydromorphone significantly suppressed secondary hyperalgesia and acute thermal nociception. Oral lamotrigine did not reduce secondary hyperalgesia or acute thermal nociception but produced side effects of severity comparable with that of oral hydromorphone. Although lamotrigine is efficacious in the management of some types of chronic neuropathic pain, the lack of effect of this agent on human experimental pain suggests that its analgesic effects depend on nerve injury-associated abnormalities, which cannot be simulated in healthy human volunteers.
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Randomized Controlled Trial Clinical Trial
Interpretation of visual analog scale ratings and change scores: a reanalysis of two clinical trials of postoperative pain.
The visual analog scale (VAS) is one of the most commonly used measures of pain intensity in pain research. However, there remain important unanswered questions concerning interpretation of specific VAS ratings and change scores. ⋯ As predicted, in assessment of the amount of change corresponding to differing levels of pain relief, percentage change in a patient's VAS score was less biased by pretreatment pain than was absolute change score. The findings also suggested that a 33% decrease in pain represents a reasonable standard for determining that a change in pain is meaningful from the patient's perspective.