​N-butyl Pentylone is a synthetic cathinone first reported in 1960s German patent literature, emerging on the recreational drug market in late 2018. Cathinone analogs have seen widespread abuse since the mid-2000s and are derived from the alkaloid cathinone found in khat. N-butyl Pentylone has been identified on illicit research chemical websites and in seized drug samples. While several similar cathinone analogs are Schedule I controlled substances, N-butyl pentylone remains uncontrolled as of mid-2020. The goal of this monograph is to identify its probable phase I metabolites using HLM assays. This study can provide insights into the metabolic pathway of N-butyl pentylone, and by analysis with high-resolution Orbitrap mass spectrometry, we aim to provide forensic toxicologists with the key ions/fragments that can help identify this novel synthetic cathinone in biological samples.