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. . Pharmacokinets of Diclofenac Sodium Absorption: Diclofenac sodium is rapidly absorbed after oral administration. It undergoes first pass metabolism and its bioavailability is 50 % only. Distribution: It is distributed in highly protein bound form. Metabolism: Diclofenac sodium is metabolised in the liver. Excretion: Drug and metabolites are primarily excreted in urine and some amount in the bile.