False-positive fentanyl screening kit results during treatment with long term injectable risperidone (Risperdal-Consta).

Fentanyl, a highly potent synthetic opioid, is a major cause of overdose deaths in the United States and worldwide. Urine drug immunoassay tests that include fentanyl in their drug panel are the common screening tool. However, false positive results may compromise test accuracy and cause grave clinical outcomes. In this preliminary report we describe 3 cases of patients with schizophrenia, who are treated with long-term injectable risperidone (Risperdal Consta) and were false positively screened for fentanyl by a rapid commercial screening kit. This finding warrants clinical attention to the possibility of inaccurate results regarding fentanyl misuse in multiple clinical settings.