Baclofen: To Screen or Not to Screen in Postmortem Blood?

Area of Science:

• Forensic Toxicology
• Clinical Pharmacology
• Drug Abuse Research

Background:

• Baclofen (BLF), prescribed for spasticity since 1972, is increasingly recognized for recreational misuse.
• Association with ethanol, GHB, pregabalin (PGL), and gabapentin (GBP) use/abuse, with reported deaths, necessitates investigation.
• Current postmortem (PM) screening lacks routine BLF analysis, obscuring the true extent of its misuse.

Purpose of the Study:

• To determine the prevalence and concentrations of BLF in UK Coroners' toxicology data.
• To investigate if BLF misuse with other substances (ethanol, GHB, PGL, GBP) contributes to mortality.
• To assess the potential underreporting of BLF-associated deaths.

Main Methods:

• Screening of 3,750 PM femoral vein blood samples for BLF between January 2016 and December 2017.
• Quantification of BLF in all positive samples.
• Analysis of co-ingested substances, including ethanol, GHB, PGL, and GBP.

Main Results:

• Baclofen (BLF) detected in 0.56% of samples, with concentrations ranging from 0.08 to 102.00 µg/mL (median 0.28 µg/mL).
• Routine screening without specific suspicion would have missed 43% of positive BLF cases, but this represents only 0.25% of the total cohort.
• Limited evidence of co-ingestion with GHB (one case), PGL/GBP (no deaths observed), or significant ethanol levels (two cases ≥50 mg%). Two cases of presumed intentional BLF overdose were identified.

Conclusions:

• Baclofen (BLF) abuse is occurring, but deaths directly attributable to its misuse are rare.
• Routine postmortem screening for BLF is not currently cost- or time-effective due to low incidence.
• Future investigations into BLF for alcoholism and drug withdrawal treatment may increase BLF-related deaths.