A fatal interaction of methocarbamol and ethanol in an accidental poisoning.

Author(s): Ferslew KE, Hagardorn AN, McCormick WF

Affiliation(s): Department of Pharmacology, Quillen-Dishner College of Medicine, East Tennessee State University, Johnson City.

Publication date & source: 1990-03, J Forensic Sci., 35(2):477-82.

Publication type: Case Reports

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 micrograms/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 micrograms/mL; bile, 927 micrograms/L; urine, 255 micrograms/L; gastric, 3.7 g; liver, 459 micrograms/g; and kidney, 83 micrograms/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.