Significance of Conventional and Alternative Biological Matrices in Evaluating the Extend of Use of New Psychoactive Substances (NPS)

New Psychoactive Substances (NPS) have flooded the illicit drug market, mimicked the effects of controlled substances while evading legal restrictions due to structural variations. Their widespread availability have led to significant public health concerns, including acute intoxication and fatalities. Consequently, developing effective detection methods is crucial to safeguard public health and enhance toxicological analysis capabilities. Conventional biological specimens include mainly blood and urine, while non-conventional mainly refer to hair. Hair testing is particularly beneficial for assessing past, chronic, sub-chronic, and, in certain cases, even acute exposure to xenobiotics, with a detection window extending up to several months. It is non-invasive, simple to collect, and allows for retrospective analysis. However, it is less effective for detecting acute exposure and may be influenced by environmental factors, leading to false results. Conversely, blood tests are effective for documenting recent drug use and are the only analyses that can correlate drug concentrations with symptomatology. The selection between hair and blood testing for NPS detection hinges on the investigation's objectives, recent or historical substance use, cost, time, and invasiveness. Given the pervasive presence of NPS in various communities, hair analysis offers a valuable tool for assessing the extent of use among different populations.