Pain
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Comparative Study Clinical Trial
Significantly higher methadone dose for methadone maintenance treatment (MMT) patients with chronic pain.
The aim of this study is to characterize patients with chronic pain in methadone maintenance treatment (MMT). Between September and December, 2003, 170 consecutive patients from an MMT clinic participated in a questionnaire survey on pain (duration and severity). Chronic pain was defined as current pain lasting for >or=6 months. ⋯ Patients in the non-pain group (n=76) were receiving 147.1+/-52.8 mg/day of methadone (ANOVA, F=3.1, P=0.03). We conclude that pain duration and severity significantly correlated. Although methadone was not prescribed for the treatment of pain but rather for opiate addiction, the patients in the MMT clinic with prolonged pain were prescribed a significantly higher methadone dosage compared to patients with short pain duration, and non-pain patients.
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Comparative Study
Spinal noradrenaline transporter inhibition by reboxetine and Xen2174 reduces tactile hypersensitivity after surgery in rats.
Spinal noradrenaline (NA) released in response to noxious stimuli may play an important role in suppression of nociceptive transmission. Here, we investigated the efficacy of a competitive NA transporter inhibitor (reboxetine) and a noncompetitive NA transporter inhibitor peptide, Xen2174, isolated from the Pacific cone snail, to treat tactile hypersensitivity following paw incisional surgery. Male Sprague-Dawley rats were anesthetized, an incision of the plantar aspect of the hind paw was performed, and withdrawal threshold to von Frey filaments near the surgical site determined. ⋯ The anti-hypersensitivity effect of 10 microg of Xen2174 was totally blocked by the alpha2-adrenoceptor antagonist, idazoxan, and partially blocked by the muscarinic antagonist, atropine. These data suggest that selective NA transporter inhibition suppresses post-incisional hypersensitivity through a different mechanism from that of neuropathic pain, since we previously reported that reversal of hypersensitivity by intrathecal clonidine, an alpha2-adrenoceptor agonist, following spinal nerve ligation is completely blocked by intrathecal atropine. Finally, these data suggest that intrathecal administration of Xen2174 at the time of spinal anesthesia might produce postoperative analgesia in humans.
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Comparative Study
Pronociceptive role of dynorphins in uninjured animals: N-ethylmaleimide-induced nociceptive behavior mediated through inhibition of dynorphin degradation.
Intrathecal (i.t.) administration into mice of N-ethylmaleimide (NEM), a cysteine protease inhibitor, produced a characteristic behavioral response, the biting and/or licking of the hindpaw and the tail along with slight hindlimb scratching directed toward the flank. The behavior induced by NEM was inhibited by the intraperitoneal injection of morphine. We have recently reported that dynorphin A and, more potently big dynorphin, consisting of dynorphins A and B, produce the same type of nociceptive response whereas dynorphin B does not [Tan-No K, Esashi A, Nakagawasai O, Niijima F, Tadano T, Sakurada C, Sakurada T, Bakalkin G, Terenius L, Kisara K. ⋯ NEM completely inhibited degradation of dynorphin A by soluble and particulate fractions of mouse spinal cord. Collectively, the results demonstrate that endogenous prodynorphin-derived peptides are pronociceptive in uninjured animals, and required for the NEM-induced behavior. The NEM effects may be mediated through inhibition of the degradation of endogenous dynorphins, presumably big dynorphin that in turn activates the NMDA receptor ion-channel complex by acting on the polyamine recognition site.
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Comparative Study
Dimensions of catastrophic thinking associated with pain experience and disability in patients with neuropathic pain conditions.
The objective of the present study was to examine the relative contributions of different dimensions of catastrophic thinking (i.e. rumination, magnification, helplessness) to the pain experience and disability associated with neuropathic pain. Eighty patients with diabetic neuropathy, post-herpetic neuralgia, post-surgical or post-traumatic neuropathic pain who had volunteered for participation in a clinical trial formed the basis of the present analyses. Spontaneous pain was assessed with the sensory and affective subscales of the McGill Pain Questionnaire. ⋯ Catastrophizing predicted pain-related disability over and above the variance accounted for by pain severity. The findings are discussed in terms of mechanisms linking catastrophic thinking to pain experience. Treatment implications are addressed.