(2014) 'Analgesic eects of antidepressants alone and after their local co-administration with morphine in a rat model of neuropathic pain.', Pharmacological reports., 66 (3). pp. 459-465. Further information on publisher's website: Additional information:
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IntroductionNeuropathic pain is defined as pain arising as a direct consequence of a lesion or disease affecting the somatosensory system [1]. The most frequent etiologic factors of neuropathic pain are trauma (including post-surgery scars), metabolic disturbances (e.g., diabetes mellitus) and ischemia. The pathological mechanism of neuropathic pain differs significantly from that of inflammatory pain; studies have shown that the changes in spinal gene expression under neuropathy and inflammations are different [2]. Thus, the response to antinociceptive drugs, especially opioids, is not the same. It has generally been accepted that neuropathic pain is somewhat resistant to morphine administration in clinical studies [3,4], and the reduced ability of morphine to attenuate allodynia and hyperalgesia in experimental models of neuropathic pain has been demonstrated [5][6][7][8]. For these reasons, it is a common clinical practice to use analgesic drug combinations. The primary approach to treat neuropathic pain is the use of coanalgesics such as tricyclic antidepressants (TCA); however, their systemic application is associated with significant side effects, which can hinder the desired analgesic effect. An alternative approach to this is the topical administration of analgesics. Currently, the possibility of the topical
Background:The therapy of neuropathic pain may include the use of co-analgesics, such as antidepressants, however, their desired analgesic effect is associated with significant side effects. An alternative approach to this is their local administration which has been proposed, but there is little data regarding their local co-administration with morphine and the nature of the interaction between morphine and either doxepin or venlafaxine, two antidepressant drugs that have been recently used in neuropathic pain therapies. Methods: This study was performed on rats after chronic constriction injury (CCI) to the sciatic nerve. The von Frey and Hargreaves' tests were used to assess mechanical allodynia and thermal hyperalgesia, respectively, after intraplantar (ipl) or subcutaneous (sc) administration of amitriptyline, doxepin, or venlafaxine, or their ipl co-administration with morphine on day 12-16 after inj...