Robaxin, also known as methocarbamol, does not appear on most workplace drug tests because it is not a controlled substance or narcotic, according to Drugs.com. The package insert provided by the National Institutes of Health DailyMed library notes that Robaxin may result in false positives for certain urine screening tests that are used to diagnose and track cancerous tumors.
According to Datia.org, the Substance Abuse and Mental Health Services Administration requires all federal agencies to drug test for amphetamines, THC, cocaine, opiates, and phencyclidine. Private employers may test for any particular substance but often use eight- or 10-panel drug tests, neither of which include methocarbamol. Robaxin could appear on a drug test if a private employer decided to specifically test for methocarbamol.
Although methocarbamol is not included in drug tests, the Robaxin package insert from DailyMed warns it may cause false positives in urinary tests for 5-hydroxyindoleacetic acid, abbreviated as 5-HIAA, and vanillylmandelic acid, abbreviated as VMA. According to the National Institutes of Health, methocarbamol may increase the amount of 5-HIAA, which is a chemical produced during serotonin breakdown. Mayo Clinic notes that high 5-HIAA levels indicate potential tumors in the endocrine system, and high VMA levels are present in neuroblastoma patients.
Robaxin is a central nervous system depressant that acts as a sedative and muscle relaxant, notes DailyMed. It is prescribed as part of a comprehensive pain management plan for patients with musculoskeletal issues.