Diclofenac is a nonsteroidal anti-inflammatory drug (NSAID) of the phenylacetic acid class with analgesic, anti-inflammatory, and antipyretic properties.
Its primary mechanism of action is inhibition of cyclooxygenase (COX-1 and COX-2) enzymes, leading to decreased synthesis of prostaglandins, which are mediators of pain and inflammation.
Diclofenac is available in multiple formulations: oral (sodium and potassium salts), topical gels and solutions, transdermal patches, and as diclofenac epolamine for topical use.
It is FDA-approved for the management of mild to moderate acute pain, osteoarthritis pain, rheumatoid arthritis, ankylosing spondylitis, and primary dysmenorrhea, among other indications.
Clinically, diclofenac is associated with dose-dependent gastrointestinal, cardiovascular, and renal adverse effects, similar to other NSAIDs.
Recommended oral dosages vary by indication: for osteoarthritis, 100–150 mg/day in divided doses; for rheumatoid arthritis, 150–200 mg/day in divided doses; and for primary dysmenorrhea or mild to moderate pain, 50 mg three times daily.
Topical formulations (e.g., Voltaren gel), are used for localized pain and inflammation, particularly in osteoarthritis, and are associated with lower systemic absorption and reduced risk of systemic adverse effects.
Diclofenac’s pharmacologic activity extends beyond COX inhibition, with additional effects on thromboxane-prostanoid receptors, lipoxygenase enzymes, and other pathways.