Pre-analytical stability of drugs of abuse in urine for confirmatory testing: a systematic review

Assessment of drugs of abuse in biological fluids requires thorough knowledge of stability of the drugs under various conditions, including sample collection, handling, transportation, and analysis, to ensure accurate interpretation of results. This systematic review provides an overview of the literature on the pre-analytical stability of selected clinically relevant drugs of abuse in urine. A systematic search of the PubMed and Embase databases was conducted in October 2020 and February 2024. The search strategy encompassed over 20 drugs and their relevant metabolites tested in urine, focusing on studies that examined the stability of opioids, amphetamine-like drugs (including ephedrine, cocaine and cathinone), and cannabis using mass spectrometry. A total of 2,688 records were identified, and 71 studies met the inclusion criteria. These studies evaluated storage conditions including room temperature, refrigeration, freezing, and deep freezing, as well as the effects of freeze-thaw cycles. Most drugs demonstrated stability for months when refrigerated or frozen, and deep freezing and freeze-thaw cycles generally had minimal impact on stability. However, storage at room temperature showed limited stability, with cathinone, cannabis, morphine, codeine, and cocaine being particularly prone to degradation under different conditions. This review offers valuable insights into the storage stability of a wide range of drugs of abuse in urine, serving as a practical resource for healthcare professionals and others working with these substances in laboratory settings.