- Medical history: a) Paticipant has a known or suspected intolerance or hypersensitivity to guaifenesin or methocarbamol (or closely related compounds) or any of their stated ingredients. b) Paticipant has history of upper back pain with active hypersensitive spots - trigger point in the muscles of upper back/neck/shoulder/maxillofacial regions. c) Paticipant has a current or recent history of liver and/or kidney disease, neck/back/shoulder injuries, spinal disc disease, myocardial infarction (<12 months from Visit 1) and osteoporosis. d) Subjects have history of other chronic pain e.g. headache, osteoarthritis, arthritis, lower back pain etc.