Challenges in Interpreting Unexpected Urine Drug Test Results.

Abstract

A 57-year-old man presented to his primary care physician (PCP) for a routine checkup. The patient complained of chronic pain from osteoarthritis in both shoulders, hands, and knees, and reported 5+ h of stiffness in the morning. The patient also had a history of gastric bypass, cholelithiasis, and insomnia. The patient was prescribed oxycodone (5 mg tabs, up to 4 tabs per day as needed) for pain, as well as zolpidem, amlodipine, and ibuprofen. During the clinic visit the PCP noted that the patient's affect seemed odd and decided to collect a urine sample to perform a urine drug screen because the patient was requesting a refill of oxycodone. The urine drug screen was performed and tested positive for oxycodone, opiates, ethanol, and benzodiazepines. The Toxicology Consultation service was contacted to help explain the unexpected positive benzodiazepines and opiates results. To elucidate the cause of the positive opiates results, the urine specimen was sent for definitive testing by LC-MS/MS for an expanded panel of opiates/opioids. It identified oxycodone (5000 ng/mL), oxymorphone (51 ng/mL), and noroxycodone (6600 ng/mL) only. No other common opiates/opioids were detected (i.e., morphine, codeine, hydrocodone, hydromorphone, norhydrocodone). Definitive testing for a panel of benzodiazepines was also performed on the urine specimen and identified nordiazepam (140 ng/mL), oxazepam (360 ng/mL), …