Laboratory monitoring of OxyContin (oxycodone): clinical pitfalls

Some patients have headaches that are refractory to standard treatments, and they require chronic administration of opioid analgesics. The use of opioids in a clinical setting must be closely monitored due to the medications' potential for addiction, abuse, and fatal interactions. Limited access to opioids and the demand for them outside the clinical setting leads to another danger. Patients can mislead their providers into prescribing opioids, intending to sell the medications instead of using them to alleviate their own pain. For protection of the patient, as well as the community, it is vital that such activity be prevented. We recently encountered a patient we suspected of abusing or misusing OxyContin (oxycodone). In order to determine whether the patient was taking the medication as prescribed, we ordered a urine-based immunoassay drug screen. The results were negative; the patient appeared to not have oxycodone in his system. Based on these results, we dismissed the patient from our practice. At the patient's request, a second test was performed, this time using gas chromatography-mass spectrometry. It indicated that the patient did indeed have sufficiently high levels of oxycodone in the urine. The minimum level threshold was too high to detect the presence of oxycodone in the immunoassay. We would like to help prevent future misunderstandings such as we experienced. To do so, we will first present the case of our patient, followed by a discussion of the actions taken. Finally, we will provide an overview of analgesic monitoring systems.