Acemetacin is prescribed to ease pain and reduce inflammation in people with painful muscles or joints. Typical conditions it is prescribed for include osteoarthritis, rheumatoid arthritis and ankylosing spondylitis. It is also prescribed to ease pain after surgical operations. Acemetacin works by blocking the effect of natural substances called cyclo-oxygenase (COX) enzymes. These enzymes help to make other chemicals in the body, called prostaglandins. Some prostaglandins are produced at sites of injury or damage, and cause pain and inflammation. By blocking the effect of COX enzymes, fewer prostaglandins are produced, which means pain and inflammation are eased.