EMERGING DRUGS OF ABUSE IN THE CHRONIC PAIN POPULATION: A CLINICAL PHARMACOLOGY PERSPECTIVE ON KRATOM, NOVEL SYNTHETIC OPIOIDS, DESIGNER BENZODIAZEPINES, GABAPENTINOIDS, XYLAZINE, AND KETAMINE

F. Breve¹, G. Varrassi², J. Pergolizzi³, R. Raffa⁴ | ¹Mid Atlantic PharmaTech Consultants LLC, Ventnor City, NJ, USA; Temple University School of Pharmacy, Philadelphia, PA, USA; ²Fondazione Paolo Procacci, Rome, Italy; ³NEMA Research Inc., Naples, FL, USA; ⁴Temple University School of Pharmacy, Philadelphia, PA, USA; University of Arizona College of Pharmacy, Tucson, AZ, USA

Background and Aims. Chronic pain patients increasingly self-medicate with unregulated and emerging psychoactive substances, driven by opioid prescribing restrictions, cost barriers, and the widespread perception that "natural" alternatives are safe. Pain specialists face a critical knowledge gap: none of the substances reviewed in this analysis are detectable on standard immunoassay urine drug screens, rendering conventional monitoring strategies fundamentally insufficient for this evolving patient population. The aim is to characterize the pharmacology, clinical risk profiles, drug interaction mechanisms, regulatory status, and toxicological detection requirements of six emerging drug classes of direct relevance to pain medicine practice: kratom (Mitragyna speciosa), novel synthetic opioids (nitazenes), designer benzodiazepines, gabapentinoids (in the context of misuse), xylazine, and ketamine.
Methods. Narrative review of published peer-reviewed literature, pharmacovigilance databases, and regulatory agency communications (FDA, DEA, EMCDDA, EMA), supplemented by large-scale survey data. Analysis was conducted from a clinical pharmacology perspective with primary emphasis on patient safety implications for pain medicine practitioners operating in international settings.
Results. Kratom, used by an estimated 1.7 billion individuals globally, produces biphasic dose-dependent effects via mu-opioid receptor agonism and CYP3A4/CYP2D6 inhibition, creating clinically silent pharmacokinetic interactions with co-prescribed analgesics. Nitazenes — benzimidazole-class full MOR agonists 10–100× more potent than morphine — are increasingly detected in illicit opioid supplies across North America and Europe and require LC-MS/MS for identification, which is unavailable on standard panels. Designer benzodiazepines (etizolam, clonazolam, and flualprazolam) escape standard immunoassay detection entirely and produce respiratory depression synergistic with prescribed opioids. Gabapentinoid misuse is implicated in over 35% of opioid-related deaths in the United Kingdom. Xylazine adulteration of fentanyl creates a dangerous partial naloxone-response scenario with pathognomonic necrotic wound presentation. Ketamine’s expanding therapeutic use coexists with irreversible uropathy documented in 20–30% of chronic recreational users. Across all six substance classes, standard urine drug screens are uniformly inadequate; targeted confirmatory testing (LC-MS/MS, GC-MS) and specific, non-judgmental patient questioning are required.
Conclusions. Emerging drugs of abuse represent a clinically urgent and underrecognized patient safety challenge in pain medicine. Pain specialists must adopt substance-specific screening strategies, update patient communication frameworks, and engage professional societies to address the regulatory and educational gaps the rapidly evolving landscape exposes. Collaborative international pharmacovigilance and sustained research investment are essential to protect patients across jurisdictions.