. diclofenac belongs to the family of non-steroidal anti-inflammatory drugs (NSAIDs) . It works by inhibiting cyclooxygenase. These enzymes help make chemicals in the body called prostaglandins, which are released at sites of injury and cause pain and inflammation It is used to reduce fever and reduce pain and inflammation in the following cases: Rheumatic pain. arthritis. menstrual pain Inflammation of muscles and tendons. Headaches of all kinds. Toothache. Sports injuries. side effects of this medicine: Abdominal pain. diarrhea. Fatigue. burning sensation stomach upset; The appearance of signs of allergy, such as a rash or redness.