Most muscle relaxants, such as Flexeril, do not show any adverse drug interactions with nabumetone. However, a group of people taking nabumetone and chlorzoxazone were studied for drug interactions. Very few people exhibited specific symptoms such as stomach problems, serotonin syndrome (increased serotonin levels causing fever, shivering and increased heart rate), agitation, confusion, diarrhoea, kidney-related anaemia, possible psychotic disorders, chronic kidney disease in males, kidney failure and gastro-oesophageal reflux disease.
You should consult your physician while taking any other muscle relaxants along with nabumetone. Get a free second opinion here.