RESUMEN
INTRODUCTION: Urine drug screens (UDS) assist in clinical planning and assessment of adherence in opioid agonist treatment (OAT). Urine drug screens may also be used in criminal justice and child protection settings. Buprenorphine (BPN) UDS testing is complex. Immunoassay often does not detect BPN and gas chromatography-mass spectrometry (GC-MS) is needed. A limited understanding of testing can negatively influence UDS interpretation and clinical decision making. OBJECTIVES: The primary aim was to determine detection rates of BPN in UDS in participants on BPN or buprenorphine/naloxone (BNX) treatment. The secondary aim was to identify if comorbidities, sex, co-prescribed medications, or dosing site and observation were associated with BPN detection. SETTING: Public outpatient clinic in a specialist addiction treatment service. DESIGN/PARTICIPANTS: In this retrospective observational study, records of clients on supervised BPN/BNX treatment between September 2017 and 2018 were reviewed. MEASURES: Data extracted included UDS results, age, sex, indication for BPN, frequency of observed doses, dose of BPN, dosing site, comorbid medical conditions, and medications. RESULTS: One hundred and sixty-one medical records were reviewed. Ninety-seven (60 percent) underwent screening urine immunoassay. Of these 97, 51 (53 percent) had further GC-MS testing for BPN of which 22 (43 percent) did not detect BPN despite directly observed OAT. Co-prescription of medications known to interact with cytochrome P450 3A4 was associated with nondetection of BPN (p < 0.05). No significant association between median dose, dosing site, and observed dosing and BPN detection was identified. CONCLUSION: Urine drug testing for BPN is complex. Failure to detect BPN does not betoken nonadherence to treatment and is associated with co-prescription of drugs interacting with cytochrome P450 3A4.