Pain o soma 500 mg tablet is the brand name for carisoprodol, a muscle relaxant that works centrally to treat pain and discomfort in muscles caused by accidents or spasms. Pain in the muscles is eased by Prosoma 500, which blocks pain signals between nerves and the brain. The medicine comes in pills that you take by mouth. Each pill has 500 mg of the main ingredient Carisoprodol. Prosoma 500 is generally only suggested for a short time.