Postmortem Metaxalone (Skelaxin®) Data from North Carolina

The North Carolina Office of the Chief Medical Examiner Toxicology Laboratory identified 61 cases from 2002 to 2014 where metaxalone was detected during routine postmortem drug screening in support of a determination of cause and manner of death. Decedents were divided into groups based on the manner of death with the goal of studying metaxalone concentrations in overdose and non-overdose situations (natural, accident, suicide and undetermined). Subgroups were established for cases in which metaxalone contributed to the cause of death (attributed) and cases in which it did not (unattributed). Attributed cases were divided into those where metaxalone additively combined with other drugs and cases in which the drug was present in sufficient amounts to be the primary cause of death, regardless of other drugs present and the concentrations of those drugs. The mean metaxalone concentration for the additive deaths was 14.2 mg/L with a median value of 11 mg/L (n = 18) and a mean metaxalone concentration of 36.7 mg/L with a median value of 32 mg/L (n = 9) for primary deaths. For unattributed metaxalone concentrations, the mean was 3.4 mg/L with a median value of 2.9 mg/L (n = 31). Of the 61 cases, 34% fall at or below a therapeutic concentration of ≤4 mg/L. The selected case studies offer valuable information regarding postmortem interpretation.