Diclofenac: an update on its mechanism of action and safety profile

Abstract

Background:

Diclofenac is a proven, commonly prescribed nonsteroidal anti-inflammatory drug (NSAID) that has analgesic, anti-inflammatory, and antipyretic properties, and has been shown to be effective in treating a variety of acute and chronic pain and inflammatory conditions. As with all NSAIDs, diclofenac exerts its action via inhibition of prostaglandin synthesis by inhibiting cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) with relative equipotency. However, extensive research shows the pharmacologic activity of diclofenac goes beyond COX inhibition, and includes multimodal and, in some instances, novel mechanisms of action (MOA).

Data sources:

Literature retrieval was performed through PubMed/MEDLINE (through May 2009) using combinations of the terms diclofenac, NSAID, mechanism of action, COX-1, COX-2, and pharmacology. Reference citations resulting from publications identified in the literature search were reviewed when appropriate.

Methods:

This article reviews the established, putative, and emerging MOAs of diclofenac; compares the drug’s pharmacologic and pharmacodynamic properties with other NSAIDs to delineate its potentially unique qualities; hypothesizes why it has been chosen for further recent formulation enhancement; and evaluates the potential effect of its MOA characteristics on safety.

Discussion:

Research suggests diclofenac can inhibit the thromboxane-prostanoid receptor, affect arachidonic acid release and uptake, inhibit lipoxygenase enzymes, and activate the nitric oxide–cGMP antinociceptive pathway. Other novel MOAs may include the inhibition of substrate P, inhibition of peroxisome proliferator activated receptor gamma (PPARγ), blockage of acid-sensing ion channels, alteration of interleukin-6 production, and inhibition of N-methyl-D-aspartate (NMDA) receptor hyperalgesia. The review was not designed to compare MOAs of diclofenac with other NSAIDs. Additionally, as the highlighted putative and emerging MOAs do not have clinical data to demonstrate that these models are correct, further research is necessary to ascertain if the proposed pathways will translate into clinical benefits. The diversity in diclofenac’s MOA may suggest the potential for a relatively more favorable profile compared with other NSAIDs.

Key words::

• COX 1 and 2
• Diclofenac
• Enzyme inhibition
• Equipotency
• Mechanism of action
• NSAID
• Receptor inhibition

Transparency

Declaration of funding

This research was supported by Xanodyne Pharmaceuticals, Inc.

Declaration of financial/other relationships

T.J.G. has disclosed that he has received grant/research support from Baxter, Eisai, Schering-Plough, Acacia, and Aspect, and that he has participated in speakers bureaus for Baxter, Edwards Lifesciences, Fresenius, Xanodyne Pharmaceuticals, Inc., and GlaxoSmithKline.

Peer reviewers may receive honoraria from CMRO for their review work. The peer reviewers have disclosed no relevant financial relationships.

Acknowledgment

The author would like to thank Xanodyne Pharmaceuticals, Inc., for support of this manuscript. He also thanks Lamara D. Shrode, PhD, of The JB Ashtin Group, Inc., who, on the behalf of Xanodyne Pharmaceuticals, Inc., provided editorial assistance. This editorial assistance was funded by Xanodyne Pharmaceuticals, Inc.

Notes

*Voltaren is a registered trade name of Novartis, East Hanover, NJ, USA.

†Voltaren-XR is a registered trade name of Novartis, East Hanover, NJ, USA.

‡Cataflam is a registered trade name of Novartis, East Hanover, NJ, USA.

§Arthrotec is a registered trade name of Pfizer, New York, NY, USA.

*Zipsor is a registered trade name of Xanodyne Pharmaceuticals, Inc., Newport, KY, USA.

†ProSorb dispersion technology licensed to Xanodyne Pharmaceuticals, Inc., Newport, KY, USA, from AAIPharma Inc., Wilmington, NC, USA.

‡Voltaren Gel is a registered trade name of Novartis, East Hanover, NJ, USA.

§Solaraze is a registered trade name of PharmaDerm, Melville, NY, USA.

¶Flector is a registered trade name of King Pharmaceuticals, Bristol, TN, USA.

⊥Pennsaid is a registered trade name of Nuvo Research, Varennes, Quebec, Canada.