Title : False-Positive Phencyclidine (PCP) result on 11-Panel Urine Drug Screen (UDS) in a 17-year-old Adolescent with long-term venlafaxine use
Abstract:
Venlafaxine is an antidepressant belonging to the class of serotonin-norepinephrine reuptake inhibitors (SNRIs) that is US Food and Drug Administration (FDA) approved to treat and manage symptoms of depression, anxiety, and other mood disorders in adults. Phencyclidine (PCP) is a dissociative anesthetic that became popular for recreational use in the 1970s. PCP use has rapidly increased in recent years; between 2005 and 2011, ED visits related to PCP have increased five to sixfold. We describe an adolescent patient who likely had a false-positive phencyclidine (PCP) result detected with an 11-panel urine drug screen (UDS) in an outpatient setting of long-term use of therapeutic venlafaxine extended-release (XR) for the treatment of recurrent MDD and GAD. We believe that this may be the first case report to characterize this phenomenon in a young patient in the absence of an acute overdose. There is some evidence that venlafaxine’s major metabolite, O-desmethylvenlafaxine (ODV), is in part associated with producing false-positive PCP results. One study prepared concentrations of venlafaxine or ODV in the laboratory, which resulted in positive results for PCP, indicating that there is some cross-reactivity between the drug and the metabolites with the PCP assay reagent. The other case report published in the literature among pediatric patients occurred in the setting of acute overdose. Our case presentation is unique in that it occurred in the absence of acute overdose and the medication was taken long-term. While there is a possibility that there may have been PCP use by the patient, the false-positive PCP result and subsequent discussion can lead to the erosion of trust between the patient and the provider. Repeatedly asking about substance misuse in the absence of misuse can lead to continued mistrust. Patients are often in vulnerable states during their psychiatry visits since they share personal details about their lives that are seldom shared with others. Thus, we believe there is a need to warn patients regarding the association between venlafaxine extended release (XR) use and false-positive PCP results as a part of transparent communication during patient-centered care. Venlafaxine remains one of the most prescribed medications in the United States for the treatment of depression, anxiety, and other mood disorders. There is a need to further study the association between venlafaxine metabolism and PCP assay reagents commonly used in UDS, particularly in pediatric patients, to improve patient-centered care.
Audience Take Away Notes:
- We believe that this may be the first clinical presentation to characterize a phenomenon of false-positive PCP result in a young patient in the absence of an acute overdose.
- Young patients are particularly vulnerable populations and moreover, false-positive results can erode the trust between the patient and the provider. There is a need to warn patients and clinicians regarding this possible association between venlafaxine XR use and false-positive PCP results to engage in patient-centered care.
- New research efforts can be directed to improve accuracy and detection methods.
