Phenylbutazone-13C12 is the 13C12 labeled Phenylbutazone. Phenylbutazone is an efficient reducing cofactor for the peroxidase activity of prostaglandin H synthase (PHS). Phenylbutazone, a hepatotoxin, is a nonsteroidal anti-inflammatory agent (NSAID). Phenylbutazone induces muscle blind-like protein 1 (MBNL1) expression and has the potential for ankylosing spondylitis research.