Ropinirole metabolite mimics a new psychoactive substance (4-HO-MET) in LC-MS/MS.

Area of Science:

• Analytical Chemistry
• Forensic Toxicology
• Pharmacology

Background:

• Liquid chromatography tandem mass spectrometry (LC-MS/MS) is a reliable method for detecting new psychoactive substances (NPS) in clinical and forensic toxicology.
• False positives can arise, leading to significant legal consequences.
• Accurate identification of NPS is crucial for patient care and legal proceedings.

Observation:

• A clinically implausible finding of 4-hydroxy-N-methyl-N-ethyltryptamine (4-HO-MET), a NPS, was detected in a urine specimen via LC-MS/MS.
• The interference was caused by N-despropyl-ropinirole, a metabolite of ropinirole, due to high structural similarity with 4-HO-MET.
• Standard spectral library matching failed to differentiate between the NPS and the interfering metabolite.

Findings:

• N-despropyl-ropinirole interferes with 4-HO-MET detection in LC-MS/MS toxicology screening.
• Structural similarities between drugs and metabolites can lead to misidentification.
• Rigorous review of mass spectra, including relative ion ratios, is essential for accurate identification.

Implications:

• Emphasizes the critical role of clinical context and drug history in interpreting toxicology results.
• Highlights the need for scientists and pathologists to collaborate for accurate analysis.
• Underscores the importance of understanding drug metabolism in troubleshooting and result interpretation to prevent erroneous reporting.