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Analgesic effects of antidepressants alone and after their local co-administration with morphine in a rat model of neuropathic pain

Lookup NU author(s): Dr Ilona Obara

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Abstract

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 injury. Results The ipl administration of amitriptyline (3, 15 mg), doxepin (1, 5, 10, 15 mg), or venlafaxine (2, 7 mg) was effective in antagonizing CCI-induced allodynia. Their sc injection at a site distal to the injured side, did not induce alterations in pain thresholds, which supports the local mode of action. Of the three antidepressants used in this study, only ipl co-administration of amitriptyline with morphine significantly enhanced its effect in contrast to doxepin and venlafaxine, both of which weakened the analgesic effect of morphine. Conclusions In summary, the results suggest that when amitriptyline (but not doxepin or venlafaxine) is locally co-administered with morphine the effectiveness under neuropathic pain is enhanced, although additional studies are necessary to explain differential mechanisms of interaction of antidepressant drugs with morphine after local administration. © 2014 Institute of Pharmacology, Polish Academy of Sciences. All rights reserved.

Publication metadata

Author(s): Jagla G, Mika J, Makuch W, Obara I, Wordliczek J, Przewlocka B

Publication type: Article

Publication status: Published

Journal: Pharmacological Reports

Year: 2014

Volume: 66

Issue: 3

Pages: 459-465

Print publication date: 01/06/2014

Online publication date: 03/04/2014

Acceptance date: 18/11/2013

ISSN (print): 1734-1140

Publisher: Elsevier

URL: https://doi.org/10.1016/j.pharep.2013.11.004

DOI: 10.1016/j.pharep.2013.11.004

PubMed id: 24905524

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