The journal of pain : official journal of the American Pain Society
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Morphine is one of the main analgesics in cancer-induced bone pain (CIBP). To investigate the efficacy of morphine in CIBP and alteration in dorsal horn pathophysiology, systemic morphine was administered (3 mg/kg) bi-daily between days 11 and 15 after MRMT-1 carcinoma cell injections (compared with a single injection (3 mg/kg) of morphine on day 15, and acute spinal morphine (0.1, 1, 10 microg/50 microL). The chronic systemic morphine schedule significantly attenuated pain behavior (von Frey 15 g; P < .01) to a greater extent than acute systemic morphine (von Frey 15 g; P < .05). In vivo electrophysiology (day 15 chronic systemic morphine) showed an attenuation of hyperexcitable wide dynamic range (WDR) neurons, but the abnormal raised WDR to nociceptive specific neuronal ratio remained. Acute spinal morphine attenuated electrical and natural WDR neuronal response in shams at a lower dose (1 microg) compared with cancer (10 microg). Chronic morphine is more effective at attenuating pain-related behaviors than single doses, although the dorsal horn retains a pathophysiologic characterization. ⋯ This study confirms the resemblance of the rat model to human CIBP with respect to the efficacy of morphine and further suggests that adjuvant therapy is required to reverse the dorsal horn pathophysiology.
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The results of previous studies using retrospective methods or small samples have suggested that there may be psychosocial risk factors for postherpetic neuralgia (PHN). We conducted a prospective study in which 110 patients with herpes zoster were assessed within the first month after rash onset with measures of acute pain and five broad domains of psychosocial functioning-physical, role, social, and emotional functioning, and stress and social support. Twenty of the 102 patients with follow-up data were diagnosed with PHN, defined as pain that had persisted for 4 months after rash onset. Measures of role functioning, personality disorder symptoms, and disease conviction during herpes zoster each made independent contributions to predicting either presence or intensity of PHN in logistic and linear regression analyses that controlled for relevant demographic and clinical variables, including age and acute pain intensity. These findings indicate that psychosocial variables are risk factors for the development of PHN. ⋯ The results of this prospective study of patients with herpes zoster suggest that future research on the mechanisms and prevention of PHN should consider psychosocial as well as neurobiologic processes.
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Agreement between patients' and health professionals' perceptions has been shown to be low to moderate for different aspects of the patients' pain experience. Little is known, however, about patient-physiotherapist agreement in low back pain. The study objectives were to describe patient-physiotherapist agreement for low back pain intensity and functional limitations, and to identify correlates of agreement. A cross-sectional design was used. Seventy-eight patients with acute/subacute nonspecific low back pain and their respective physiotherapists were included in the study. After the initial physiotherapy consultation, patients and physiotherapists completed a Numerical Rating Scale and the Roland-Morris Disability Questionnaire. Intraclass correlation coefficients (ICC) were used to measure chance-corrected agreement. Patients' and physiotherapists' mean ratings were also compared using paired t tests. Multiple regression analyses were conducted to identify factors associated with agreement measures. The level of agreement was moderate for pain intensity (ICC = 0.55, 95% confidence interval [CI]: 0.38-0.69) and functional limitations (ICC = 0.56, 95% CI: 0.22-0.74). Both variables were rated significantly (P < .05) lower by the physiotherapists than by the patients. Higher ratings by the patients for pain and functional limitations were related to higher differences in perceptions between patients and physiotherapists. This report shows that physiotherapists' perceptions of their patients' pain intensity and functional limitations often differ from their patients'. ⋯ The findings of this study indicate that there are frequent discrepancies between patients' and physiotherapists' perceptions of the patients' low back pain experience. Gaining a better understanding of the level of patient-physiotherapist agreement and identifying the correlates of agreement may help improve physiotherapists' interventions with people with low back pain.
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Chronic lumbar radicular pain is the most common neuropathic pain syndrome. This was a double-blind, randomized, 2-period crossover trial of topiramate (50 to 400 mg) and diphenhydramine (6.25 to 50 mg) as active placebo to assess the efficacy of topiramate. Each period consisted of a 4-week escalation, a 2-week maintenance at the highest tolerated dose, and a 2-week taper. Main outcome was the mean daily leg pain score on a 0 to 10 scale during the maintenance period. Global pain relief was assessed on a 6-level category scale. In the 29 of 42 patients who completed the study, topiramate reduced leg pain by a mean of 19% (P = .065). Global pain relief scores were significantly better on topiramate (P < .005). Mean doses were topiramate 200 mg and diphenhydramine 40 mg. We concluded that topiramate treatment might reduce chronic sciatica in some patients but causes frequent side effects and dropouts. We would not recommend topiramate unless studies of alternative regimens showed a better therapeutic ratio. ⋯ The anticonvulsant topiramate might reduce chronic lumbar nerve root pain through effects such as blockade of voltage-gated sodium channels and AMPA/kainite glutamate receptors, modulation of voltage-gated calcium channels, and gamma-aminobutyric acid agonist-like effects.
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The present studies were conducted to examine functional consequences of postnatal chronic inflammation, initiated during a critical developmental period, on capsaicin-evoked hyperalgesia and neuronal activation in adulthood. Rats received a unilateral intraplantar injection of complete Freund's adjuvant (CFA; diluted 2:1 in saline) on postnatal day 0 (P0-CFA) or 14 (P14-CFA). Separate groups received an equivalent volume of saline on P0 (P0-vehicle) or were untreated (P0-untreated). Increases in capsaicin-evoked thermal and mechanical hyperalgesia and allodynia were observed in adult P0-CFA-treated rats relative to control conditions. By contrast, this enhancement was absent in P14-CFA-treated rats, suggesting that the developmental period differentially affects the appearance of the observed behavioral phenotype. Capsaicin-evoked nocifensive behavior was also lower in P14-CFA-treated rats relative to P0-CFA-treated rats. Capsaicin-evoked Fos protein expression was increased in the superficial and neck regions of the dorsal horn of adult P0-CFA-treated rats relative to P0-vehicle-treated rats. These changes were absent in the nucleus proprius and ventral horn. The present data are consistent with the hypothesis that neonatal chronic inflammation permanently alters sensitivity to pain in adulthood, consistent with modulation of primary afferent activation and central sensitization in response to a subsequent nociceptive challenge in adulthood. ⋯ Chronic inflammation during development can induce profound alterations in sensory processing later in life. Here we show that long-term inflammation initiated at critical developmental stages sensitizes both behavioral and neuronal responses to nociceptor stimulation in adulthood. An ongoing sensitization of the spinal cord is induced by the postnatal inflammatory insult.