Entacapone sodium salt is primarily used as a pharmaceutical agent in the treatment of Parkinson's disease. It functions as a catechol-O-methyltransferase (COMT) inhibitor, which helps to prolong the therapeutic effect of levodopa by preventing its breakdown in the body. This allows for more consistent dopamine levels in the brain, improving motor control and reducing the "wearing-off" phenomenon often experienced by patients. It is typically administered in combination with levodopa and carbidopa to enhance its efficacy and manage symptoms more effectively.