Ask the Expert: Cash Patient on High-Dose Oxycodone With Negative Urine Screens
QUESTION: A 38-year-old man who weighs 280 lbs owns his own business and takes 300 to 450 mg of oxycodone 30-mg tablets each day. He attends the pain clinic with his wife who is a licensed registered nurse. He and his wife state that with opioids he works full time. The problem is that recent urine screens show no oxycodone. Both patient and wife claim he faithfully takes his oxycodone as prescribed. What should the physician do?
ANSWER: Before trying to figure out the patient’s motivations, effect of his weight, his job, and paying cash, the first step is to confirm that, indeed, the patient’s urine contained no oxycodone. The most likely explanation for this apparent finding is that the wrong test was ordered. The standard urine drug screen for opioids, an immunoassay, detects only natural opioids, but not synthetics or semisynthetics—including fentanyl, oxycodone, and oxymorphone—which will be reported as negative. Accordingly, the simplest course when ordering a urine drug test for any patient on opioids is to list the opioids the patient is being prescribed, and request that all be tested for. This will result in additional testing for those drugs that would not show up on the screening. Confirmatory testing by gas chromatography/mass spectrometry or high-performance liquid chromatography will detect these drugs. In the case of prescribed oxycodone, such follow-up testing will also usually come back positive for oxymorphone, which is a metabolite of oxycodone.1
If these follow-up tests confirm the absence of oxycodone and its metabolite, then you can assume that, indeed, the patient did not take his prescribed oxycodone. When patients are prescribed oxycodone for breakthrough pain and take it intermittently, another legitimate reason for a negative urine drug test is that more than 24 hours have elapsed since the last dose. However, if a patient is being prescribed up to 450 mg of oxycodone per day, it is most likely that it is being prescribed on the basis of round-the-clock dosing. With this patient, if the confirmatory test is negative, then it’s time for an honest discussion with the patient. Some possibilities are that the patient took more than the prescribed amount and ran out early, or that he is diverting his oxycodone rather than taking it. If you are not given an explanation that is consistent with the test results, then it is reasonable to stop prescribing opioids to this patient.