Discharging a Patient Suspected of Diversion
Question: I recently prescribed oxycodone and acetaminophen (Percocet) 5 mg four times per day to a patient who had tripped and fallen and sustained some painful injuries. When she asked for a refill earlier than I had expected, I ordered a urine drug screen, which came back negative for opioids. She swore she was taking the Percocet, but I discharged her from my practice because I believe she must have been diverting the drug. Am I justified in my conclusion?
Answer: Not if your conclusion was based solely on the urine drug screen. The immunoassay used in the usual urine drug screen reacts only with natural opioids (such as morphine, hydrocodone, hydromorphone, and codeine). This test is likely to miss semisynthetic and synthetic opioids (such as fentanyl, oxycodone, and oxymorphone), although very high doses of semisynthetic opioids (eg, oxycodone, oxymorphone) may be picked up on the immunoassay. To identify specific drugs and quantify their concentrations in the urine, laboratories offer gas chromatography/mass spectrometry or high-performance liquid chromatography. Unexpected positive and negative immunoassay results should be confirmed by one of these more specific techniques. To avoid making mistakes such as erroneously firing patients who indeed have taken their prescribed fentanyl or oxycodone, a good approach is to write on the lab slip order “urine drug screen + oxycodone” or whatever other controlled substances the patient was prescribed.1 And when the confirmatory urine test for oxycodone comes back also positive for both oxycodone and oxymorphone, recognize that this too is an expected finding: oxymorphone is the chief metabolite of oxycodone.2 You can read more in the following references.
Jennifer Schneider, MD, PhD
Internal Medicine, Addiction Medicine, and Pain Management