Pain
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Clinical Trial
Cancer breakthrough pain characteristics and responses to treatment at a VA medical center.
The purpose of this study is to analyze cancer breakthrough pain (BP) characteristics and how BP responds to conventional cancer pain management. Seventy-four cancer pain patients with worst pain severity >or=4 out of 10 completed the Brief Pain Inventory (BPI), Memorial Symptom Assessment Scale-Short Form, Functional Assessment Cancer Therapy and Breakthrough Pain Questionnaires (BPQ) at an initial interview. Agency for Health Care Policy and Research (AHCPR) cancer pain management guidelines were followed. ⋯ The study confirmed the applicability of the BPQ to an US veteran population, and that pain management following the AHCPR guidelines is effective for a group of patients with cancer related BP. Underlying pain syndromes and the BP location may influence the response of BP to treatment. Patients with bone pain located in the spine, back, and pelvis may be at risk for resistant BP.
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In this paper we compare two innovative models of movement-related pain: tumor-induced nociception following implantation of fibrosarcoma cells into bone and muscle inflammation-induced nociception following injection of the irritant carrageenan into muscle. Importantly, using the grip force test, an assay of movement-related hyperalgesia, both non-malignant and malignant pain are examined in parallel. Movement-related hyperalgesia, known clinically as a specific type of 'breakthrough pain', is a common feature of bone cancer and is thought to be a predictor of poor response to conventional analgesic pharmacotherapy (Bruera et al., 1995, J. ⋯ Tumor-implanted mice with a level of hyperalgesia comparable to that induced by carrageenan required almost three times more morphine (ED(50) 18.5mg/kg) for equivalent attenuation of forelimb hyperalgesia. These animal models of movement-related hyperalgesia may aid in discerning the peripheral and central mechanisms underlying pain that accompanies bone metastases and distinguishing it from the pain associated with muscular inflammation. Importantly, they may also aid in predicting differences in analgesic efficacy in different types of musculoskeletal pain.
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Subunit non-selective N-methyl-D-aspartate (NMDA) receptor antagonists reduce injury-induced pain behavior, but generally produce unacceptable side effects. In this study, we examined the antinociceptive and motor effects of cone snail venom-derived peptides, conantokins G and T (conG and conT), which are selective inhibitors of the NR2B or NR2A and NR2B subtypes of the NMDA receptor, respectively. We tested the effects of conG and conT in models of tissue (formalin test), nerve injury (partial sciatic nerve ligation) and inflammation-induced (intraplantar Complete Freund's Adjuvant; CFA) pain in mice. ⋯ Finally, a single dose of conG (100 pmol, i.t.) also reduced CFA-evoked thermal and mechanical allodynia. Taken together, these results demonstrate that conantokins exhibit potent antinociceptive effects in several models of injury-induced pain. The study supports the notion that drugs directed against subtypes of the NMDA receptor, by virtue of their reduced side-effect profile, hold promise as novel therapeutic agents for the control of pain.
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Randomized Controlled Trial Clinical Trial
Immediate- or sustained-release morphine for dose finding during start of morphine to cancer patients: a randomized, double-blind trial.
A titration procedure using immediate-release morphine given 4-hourly is recommended during start of oral morphine for cancer pain. This recommendation is not based on evidence from controlled studies, and many physicians start morphine treatment with controlled-release morphine. We included 40 patients with malignant disease and pain despite treatment with opioids for mild to moderate pain in a randomized, double-blind, double-dummy, parallel-group study comparing titration with immediate-release morphine given 4-hourly with titration with sustained-release morphine given once daily. ⋯ We observed no other differences in adverse effects or health related quality of life functions between the two treatments. Similar global satisfactions with the morphine treatments were reported. In conclusion, a simplified titration using sustained-release morphine once daily is equally effective as immediate-release morphine given 4-hourly.
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Comparative Study
Age-related differences in endogenous pain modulation: a comparison of diffuse noxious inhibitory controls in healthy older and younger adults.
Despite decades of research, hundreds of studies, and a number of recent reviews, the effects of aging on the experience of pain remain poorly understood. Many prior investigators have reported increases in persistent pain conditions and diminished tolerance for certain types of laboratory-induced pain among the elderly. While explanations for these effects often propose senescent decrements in endogenous analgesic systems as a possible contributory mechanism, almost no direct empirical evidence for this hypothesis has yet emerged in human studies. ⋯ Interestingly, older adults demonstrated facilitation rather than inhibition of thermal pain during concurrent noxious cold stimulation while younger adults demonstrated some expected DNIC effects (i.e. a reduction in thermal pain ratings during heterotopic stimulation with noxious cold). Collectively, the findings of the present study suggest age-associated decrements in at least one form of endogenous analgesic response. If replicated, such findings of reduced pain-modulatory capacity in the elderly may partially explain age-related differences in the prevalence, severity, and impact of chronic pain.