Microfluidic Paper-Based Analytical Devices for On-Site Detection ofPharmaceuticals and Drugs of Abuse: A Review of Applications andInnovations

The escalating global burden of drug use disorders, affecting over 36 million individuals, necessitates rapid and accessible analytical tools for identifying both illicit substances and therapeutic pharmaceuticals. Traditional presumptive tests, such as spot tests, color tests, and thin-layer chromatography, offer initial screening capabilities at the point of need, but they often come with inherent limitations. This review highlights the growing role of microfluidic paper-based analytical devices (μPADs) as a transformative technology for on-site detection of pharmaceuticals and drugs of abuse. μPADs harness the intrinsic capillary action of paper, enabling cost-effective, portable, and rapid analysis with minimal sample preparation and no reliance on external power. We delve into the diverse applications of μPADs in forensic science and pharmaceutical analysis, including their utility for screening common illicit drugs (e.g., cocaine, opiates) and monitoring therapeutic drug levels. Furthermore, we explore recent innovations in μPADs’ design and fabrication, such as multiplexed detection, integration with smartphone-based analysis for semi-quantitative results, and advancements in detection mechanisms, which significantly enhance their sensitivity, specificity, and user-friendliness for widespread adoption in resource-limited settings and field investigations.