Volume 35, Issue 2 (March 1990)
A Fatal Interaction of Methocarbamol and Ethanol in an Accidental Poisoning
A case is presented of a fatal drug interaction caused by ingestion of methocarbamol (Robaxin®) and ethanol. Methocarbamol is a carbamate derivative used as a muscle relaxant with sedative effects. Therapeutic concentrations of methocarbamol are reported to be 24 to 41 μg/mL. Biological fluids were screened for ethanol using the Abbott TDx system and quantitated by gas-liquid chromatography (GLC). Determination of methocarbamol concentrations in biological tissue homogenates and fluids were obtained by colorimetric analysis of diazotized methocarbamol. Blood ethanol concentration was 135 mg/dL (0.135% w/v) and urine ethanol was 249 mg/dL (0.249% w/v). Methocarbamol concentrations were: blood, 257 μg/mL; bile, 927 μg/mL; urine, 255 μg/mL; gastric, 3.7 g; liver, 459 μg/g; and kidney, 83 μg/g. The combination of ethanol and carbamates is contraindicated since acute alcohol intoxication combined with carbamate usage can lead to combined central nervous system depression as a result of the interactive sedative-hypnotic properties of the compounds.