Clinical suspicion versus toxicological findings in psychoactive substance poisonings: evidence from emergency cases in Brazil (2023-2024).

INTRODUCTION: The emergence of new psychoactive substances and adulteration of illicit drugs complicate acute poisoning diagnosis. This study evaluated concordance between clinical suspicion and toxicological confirmation and factors associated with poisoning severity. METHODS: This cross-sectional observational study was conducted at the Poison Control Center of Campinas University and the analytical toxicology laboratory, Campinas, Brazil, between January 2023 and December 2024. A total of 385 cases of suspected psychoactive substance poisoning were included. Cases without biological samples or with toxicological requests unrelated to psychoactive substances were excluded. Clinical and demographic data were extracted from the DATATOX national database, and blood and urine toxicological results were obtained by chromatographic and mass spectrometric techniques. Concordance between clinical suspicion and toxicological confirmation, and associations with demographic and toxicological variables were assessed. Clinical severity was classified by the Poison Severity Score. RESULTS: Concordance between suspected and confirmed substances was low. Cocaine and cannabis were the most frequently suspected and confirmed illicit substances, while benzodiazepines, antidepressants, and antipsychotics were rarely suspected but frequently detected. Polysubstance exposures were highly prevalent, with a median of four substances per case. Severe or fatal cases were associated with a significantly higher number of detected substances and with older patient age. Fatalities were rare but consistently involved high-risk agents such as methanol and opioids. Neurological and cardiovascular symptoms predominated, with seizures strongly associated with stimulants and respiratory depression with sedative and opioid combinations. DISCUSSION: The substantial discrepancy between clinical suspicion and laboratory confirmation demonstrates that symptom-based assessment alone is insufficient for the evaluation of acute poisonings involving psychoactive substances. The routine integration of comprehensive toxicological testing may improve diagnostic confidence, facilitate the identification of unsuspected co-exposures, and enhance both patient management and toxicovigilance. CONCLUSION: Clinical suspicion alone is insufficient for accurate identification of psychoactive substances in acute poisonings. Comprehensive toxicological testing revealed frequent under recognition of benzodiazepines and therapeutic drugs, and a high prevalence of polysubstance use. Integration of laboratory confirmation into routine clinical practice is essential to improve patient care, inform toxicovigilance, and improve international surveillance of psychoactive substance use.