Diclofenac inhibits the activity of the enzyme cyclo - oxygenase, resulting in decreased formation of precursors of prostaglandins and thromboxanes from arachidonic acid. Diclofenac may block pain impulse generation via a peripheral action that may involve reduction of the activity of prostaglandins, and possibly inhibition of the synthesis or actions of other substances that sensitize pain receptors to mechanical or chemical stimulation.

Indicated for rheumatoid arthritis, osteoarthritis, and ankylosing spondylitis. Immediate - release tablets only indicated for pain and primary dysmenorrhea, and may also be used to relieve acute attacks of gout or calcium pyrophosphate deposition disease (pseudogout) and pain associated with nonrheumatic inflammatory conditions or vascular headaches.

This medication should not be used when the following medical problems exist: Allergic reaction, severe, such as anaphylaxis or angioedema, that induced by aspirin or other NSAIDs, history of; Nasal polyps associated with bronchospasm, aspirin-induced (high risk of severe allergic reactions because of cross - sensitivity); Blood dyscrasias, active or history of; Bone marrow depression (diclofenac may induce or exacerbate these conditions). Risk benefit should be considered when the following medical problems exist:
Allergic reaction, mild, such as allergic rhinitis, urticaria, or skin rash, indured by aspirin or other NSAIDs, history of (possibility of cross - sensitivity); Anemia; Asthma; Hypertension; Edema; Inflammatory or ulcerative disease of the upper or lower gastrointestinal tract; Diabetes mellitus; Hemophilia or other bleeding problems; Hepatic or renal function impairment; Stomatitis; Systemic lupus erythematosus; Porphyria, hepatic (diclofenac may precipitate an acute attack).

Embryotoxicity and other adverse effects, but not teratogenicity, demonstrated in animal studies.
FDA Pregnancy Category B.

Diclofenac is distributed into breast milk.

ln addition to the interactions listed below, the possibility should be considered that additive or multiple effects leading to impaired blood clotting and / or increased risk of bleeding may occur if any NSAID is used concurrently with any medication having a significant potential for causing hypoprothrombinemia, thrombocytopenia, or gastrointestinal ulceration or hemorrhage.
Acetaminophen, Alcohol, Potassium supplements, Anticoagulants, Heparin, Thrombolytic agents, Potassium-sparing diuretics, Lithium, Probenecid, Salicylates, Digoxin, Antidiabetic agents or insulin, Corticosteroids, Cyclosporine, Valproic acid.

Hypersensitivity reactions such as: Rhinosinusitis / asthma or angioedema / urticaria; Anaphylaxis.
Gastrointestinal problems; Dermatologic effects; Headache; Renal and hepatic function impairment; Hearing problems; CNS effects; Hyperkalemia; Edema.

Retard tablets:
Usual adult dose:
Antirheumatic (nonsteroidal anti-inflammatory)-Oral, 1 Diclofenac retard (100 mg) tablet once a day, in the moming or evening.
Note: The retard dosage form is not intended as initial therapy; the daily maintenance dose should be determined using an immediate -or delayed -release formulation. The retard dosage form may then be used, if desired, provided that the required dose can be achieved with the available strengths.
Usual pediatric dose:
Safety and efficacy have not been established.