Portrait of Samuel Tobias

Samuel Tobias, PhD

Substance use, drug policy & public health systems

BC Centre on Substance Use · University of British Columbia

Peer-Reviewed Publications

Citation metrics are available on Google Scholar.

2026
  1. Discordant drug checking results and risk reduction behaviours: Findings from the ChecKnow Study in France.
    Tobias S, Del Amo J, Albert S, Aubert M, Zerrari A, Chappard P, Ti L, Roux P.
    Drug and Alcohol Review, 2026;45(5):e70216
  2. The detection of novel nitazene-class opioids in unregulated drug markets in Canada.
    Gelgoot E, Scarfone KM, Maghsoudi N, McDonald K, Hao W, Stefan C, Beriault DR, Delaney SR, Ti L, Tobias S, Bowles JM, Werb D.
    Drug and Alcohol Review, 2026;45(5):e70189
  3. The comparative effects of prenatal exposure to methadone versus buprenorphine for opioid use disorder on neonatal outcomes: A systematic review and meta-analysis.
    Wilson LA, Tobias S, Gandhi P, Nosyk B, Buxton JA, Ti L.
    BMC Pregnancy and Childbirth, in press, 2026
  4. How population-level drug supply data are incorporated into health outcomes research: A scoping review.
    Tobias S, Bird J, Law MR, Buxton JA, Ti L.
    Epidemiologic Reviews, 2026;48(1)
  5. Temporal and regional associations between fentanyl concentrations in the unregulated drug supply and drug-related mortality in British Columbia, Canada.
    Tobias S, Bird J, Guzman SM, Palis H, Crabtree A, Hein JE, Wood E, Ti L.
    International Journal of Drug Policy, 2026;150:105200
  6. Development and validation of a fentanyl quantification model for drug checking services.
    Tobias S, Guzman SM, Hein JE, Ti L.
    Drug and Alcohol Dependence Reports, 2026;18:100415
  7. Risk reduction behaviours following the detection of unexpected drugs through community drug checking: A cross-sectional study.
    Tobias S, Grant CJ, Lysyshyn M, Roux P, Wood E, Kerr T, Ti L.
    Harm Reduction Journal, 2026;23:72
2025
  1. Emergence of medetomidine in the unregulated drug supply and its association with hallucinogenic effects.
    Sibley AL, Bedard ML, Tobias S, Chidgey BA, Phillips IG, Bell A, Dasgupta N.
    Drug and Alcohol Review, 2025;44(7):1896–1906
  2. Fentanyl concentrations in unregulated opioids and the blood of drug toxicity decedents.
    Tobias S, Tu A, Shapiro AM, Mérette SAM, Lysyshyn M, Wood E, Buxton JA, Ti L.
    AJE Advances: Research in Epidemiology, 2025;1(3):uuaf008
  3. Novel adulterants in unregulated opioids and their associations with adverse events.
    Tobias S, Angelucci A, Wood E, Buxton JA, Ti L.
    Canadian Journal of Public Health, 2025;116(3):356–363
  4. Sharing drug checking results in a Canadian setting: A multi-site analysis.
    Bird J, Tobias S, Grant C, Lysyshyn M, Tupper K, Wood E, Kerr T, Ti L.
    International Journal of Drug Policy, 2025;143:104903
  5. Detection of benzodiazepines in British Columbia's unregulated drug supply using point-of-care drug checking technologies: A validation study.
    Crepeault H, Tobias S, Angelucci A, Lysyshyn M, Wood E, Ti L.
    Drug and Alcohol Dependence, 2025;271
2024
  1. Local impact from international crises: Unregulated drug toxicity during the COVID-19 pandemic in British Columbia, Canada.
    Tobias S, Buxton JA, Ti L.
    American Journal of Public Health, 2024;114(6):587–589
  2. Motivators of and barriers to drug checking in British Columbia, Canada: Findings from a cross-sectional survey.
    Tobias S, Ferguson M, Palis H, Burmeister C, McDougall J, Liu L, Graham B, Ti L, Buxton JA.
    International Journal of Drug Policy, 2024;123:104290
  3. Fentanyl concentration in drug checking samples and risk of overdose death in Vancouver, Canada.
    Kennedy MC, Dong H, Tobias S, Buxton JA, Lysyshyn M, Tupper KW, Ti L.
    American Journal of Preventive Medicine, 2024;68(1):10–17
  4. Factors associated with obtaining prescribed safer supply among people accessing harm reduction services: Findings from a cross-sectional survey.
    Palis H, Haywood B, McDougall J, Xavier CG, Desai R, Tobias S, Burgess H, Ferguson M, Liu L, Kinniburgh B, Slaunwhite AK, Crabtree A, Buxton JA.
    Harm Reduction Journal, 2024;21:5
2023
  1. Associations with experience of non-fatal overdose in British Columbia, Canada: A repeated cross sectional survey study.
    Ferguson M, Choisil P, Lamb J, Burmeister C, Newman C, Lock K, Tobias S, Liu L, Buxton JA.
    Harm Reduction Journal, 2023;20:178
  2. Responding to changes in the unregulated drug supply: The need for a dynamic approach to drug checking technologies.
    Bhuiyan I, Tobias S, Ti L.
    American Journal of Drug and Alcohol Abuse, 2023;49(6):685–690
  3. What impact did the COVID-19 pandemic have on the variability of fentanyl concentrations in the Vancouver, Canada illicit drug supply? An interrupted time-series analysis.
    Tobias S, Grant CJ, Laing R, Lysyshyn M, Buxton JA, Tupper KW, Wood E, Ti L.
    BMJ Public Health, 2023;1:e000197
  4. Development of a neural network model to predict the presence of fentanyl in community drug samples.
    Ti L, Grant CJ, Tobias S, Hore DK, Laing R, Marshall BDL.
    PLOS ONE, 2023;18(7):e0288656
  5. Examining fentanyl and its analogues in the unregulated drug supply of British Columbia, Canada using drug checking technologies.
    Crepeault H, Socías ME, Tobias S, Lysyshyn M, Custance A, Shapiro A, Ti L.
    Drug and Alcohol Review, 2023;42(3):538–543
2022
  1. Changes in the unregulated opioid drug supply during income assistance payment weeks in Vancouver, Canada: An exploratory analysis.
    Beaulac M, Richardson L, Tobias S, Lysyshyn M, Grant C, Ti L.
    International Journal of Drug Policy, 2022;105:103707
  2. Tobias et al. respond to “Novel surveillance of the unregulated drug supply”.
    Tobias S, Lysyshyn M, Buxton J, Tupper KW, Ti L.
    American Journal of Epidemiology, 2022;191(2):253–254
  3. Time-series analysis of fentanyl concentration in the unregulated opioid drug supply in a Canadian setting.
    Tobias S, Grant CJ, Laing R, Arredondo J, Lysyshyn M, Buxton J, Tupper KW, Wood E, Ti L.
    American Journal of Epidemiology, 2022;191(2):241–247
2021
  1. Results from a mobile drug checking pilot program using three technologies in Chicago, IL, USA.
    Karch L, Tobias S, Schmidt C, Doe-Simkins M, Carter N, Salisbury-Afshar E, Carlberg-Racich S.
    Drug and Alcohol Dependence, 2021;228
  2. Identifying cocaine adulteration in the unregulated opioid drug supply in British Columbia, Canada.
    Patel P, Guzman S, Lysyshyn M, Buxton J, Kuo M, Tobias S, Matthews J, Arredondo J, Ti L.
    Canadian Journal of Addiction, 2021;12(2):39–44
  3. Is expected substance type associated with timing of drug checking service utilization? Findings from a point-of-care drug checking program in British Columbia, Canada.
    Beaulieu T, Wood E, Tobias S, Lysyshyn M, Patel P, Matthews J, Ti L.
    Harm Reduction Journal, 2021;18:66
  4. An outbreak of novel psychoactive substance benzodiazepines in the unregulated drug supply: Preliminary results from a community drug checking program using point-of-care and confirmatory methods.
    Laing MK, Ti L, Marmel A, Tobias S, Shapiro AM, Laing R, Lysyshyn M, Socías ME.
    International Journal of Drug Policy, 2021;93
  5. The utility of visual appearance on predicting the composition of street opioids.
    McCrae K, Wood E, Lysyshyn M, Tobias S, Wilson D, Arredondo J, Ti L.
    Substance Abuse, 2021;42(4):775–779
  6. Detection of synthetic cannabinoid adulteration in the unregulated drug supply in three Canadian settings.
    Ti L, Tobias S, Maghsoudi N, Milloy MJ, McDonald K, Shapiro A, Beriault D, Stefan C, Lysyshyn M, Werb D.
    Drug and Alcohol Review, 2021;40(4):580–585
  7. Drug checking identifies counterfeit alprazolam tablets.
    Tobias S, Shapiro AM, Grant CJ, Patel P, Lysyshyn M, Ti L.
    Drug and Alcohol Dependence, 2021;218
2020 and earlier
  1. Xylazine identified in the unregulated drug supply in British Columbia, Canada.
    Tobias S, Shapiro AM, Wu H, Ti L.
    Canadian Journal of Addiction, 2020;11(3):28–32
  2. Detecting fentanyl using point-of-care drug checking technologies: A validation study.
    Ti L, Tobias S, Lysyshyn M, Laing R, Nosova E, Choi J, Arredondo J, McCrae K, Tupper K, Wood E.
    Drug and Alcohol Dependence, 2020;212
  3. Assessing the limit of detection of Fourier-transform infrared spectroscopy and immunoassay strips for fentanyl in a real-world setting.
    McCrae K, Tobias S, Grant C, Lysyshyn M, Laing R, Wood E, Ti L.
    Drug and Alcohol Review, 2020;39(1):98–102
  4. Drug checking services at music festivals and events in a Canadian setting.
    McCrae K, Tobias S, Tupper K, Arredondo J, Henry B, Mema S, Wood E, Ti L.
    Drug and Alcohol Dependence, 2019;205
  5. The effect of pressure on DNA deposition by touch.
    Tobias S, Jacques GS, Morgan RM, Meakin GE.
    Forensic Science International: Genetics Supplement Series, 2017;6:e12–e14

Under Review & Preprints

  1. Fentanyl concentrations in British Columbia's unregulated opioids following decriminalization: A controlled interrupted time-series study.
    Tobias S, Law MR, McDonald K, Crabtree A, Delaney SR, Stefan C, Buxton JA, Ti L.
    Under review, 2026
  2. Fentanyl purity and overdose decline: A reexamination of geographic trends.
    Dasgupta N, Sibley AL, Gildner P, Gora-Combs K, Post LA, Tobias S, Kral A, Pacula RL.
    Preprint; under review, 2026
  3. Impact of scheduling on detection of bromazolam in the unregulated opioid supply: An interrupted time series analysis.
    Bird J, Tobias S, Palis H, Law MR, Angelucci J, Wood E, Crabtree A, Ti L.
    Under review, 2026
  4. Factors associated with drug checking service use in France: A cross-sectional study.
    Tobias S, Del Amo J, Zerrari A, Lopez C, Aubert M, Dècle P, Chappard P, Mora M, Ti L, Sagaon-Teyssier L, Roux P.
    Under review, 2026