Diclofenac Sodium Mechanism of Action of Diclofenac Sodium Diclofenac possess analgesic, anti-inflammatory and antipyretic action. It inhibits the enzyme cyclo-oxygenase and there by inhibits the synthesis of Prostaglandins (PGs). It is more potent against cyclo-oxygenase-2 enzyme as compared to other NSAIDs like Indomethacin, Naproxen etc. It reduces intracellular concentrations of free arachidonic acid in leukocyte by altering its release or uptake. . Interactions for Diclofenac Sodium Lithium & Digoxin : Blood levels of lithium and digoxin increased leading to enhanced efficacy and posible toxicity. Diuretics : Inhibits diuretics but efficacy of potassium sparing diuretics enhanced. Methotrexate : Toxicity enhanced. Salicylates : Efficacy of salicylates reduced. Cyclosporine : Increases nephrotoxicity of both agents. Hydantoins : Increases serum levels resulting in toxicity.