| ||||||||||||||
|
|
|||||||||||||
Pharmacology Program, ICBM, Faculty of Medicine, University of Chile, Santiago, Chile
Address correspondence and reprint requests to H. F. Miranda, PhD, Pharmacology Program, PO Box 70.000, Santiago 7, Chile. Address e-mail to hmiranda{at}machi.med.uchile.cl
We evaluated the noradrenergic modulation of the antinociceptive activity of diclofenac in mice using the acetic acid writhing test. Dose-responsecurves were obtained for the antinociceptive effect of diclofenac, phenylephrine, clonidine, desipramine, prazosin, and yohimbine administered both systemically and intrathecally, and ED50s were calculated. Noradrenergic modulation was evaluated by performing an isobolographic analysis of the systemic or intrathecal coadministration of fixed-ratio combinations of diclofenac with each adrenergic drug. The systemic, but not the intrathecal, combinations of diclofenac with phenylephrine or clonidine showed supraadditivity, suggesting that the activation of
1 and
2 adrenoceptors interfered with the nociceptive transmission at spinal and supraspinal levels. Supraadditive effects were not demonstrated for the intrathecal injection of diclofenac combined with phenylephrine, clonidine and a selective norepinephrine uptake inhibitor (desipramine) or adrenergic antagonists. We conclude that interaction between adrenoceptors and diclofenac can modulate antinociception by activating common or different mechanisms. Diclofenac has an antinociceptive activity that, in addition to cyclooxygenase inhibition, can be modulated by additive and supraadditive interactions with adrenergic drugs.
IMPLICATIONS: Diclofenac analgesia in mice can be modulated by interaction with adrenergic drugs. The systemic but not the intrathecal administration of phenylephrine and clonidine produced supraadditive interactions. For desipramine, prazosin, and yohimbine, supraadditive interactions were not statistically demonstrated. The coadministration of drugs inducing supraadditive effects could be clinically relevant for the treatment of chronic pain because of reduction of doses and side effects.
This article has been cited by other articles:
![]() |
K. R. Schmelzer, B. Inceoglu, L. Kubala, I.-H. Kim, S. L. Jinks, J. P. Eiserich, and B. D. Hammock Enhancement of antinociception by coadministration of nonsteroidal anti-inflammatory drugs and soluble epoxide hydrolase inhibitors PNAS, September 12, 2006; 103(37): 13646 - 13651. [Abstract] [Full Text] [PDF] |
||||
|