Furosemide as a potential unintended urine drug screen confounder during methadone maintenance treatment.

Patients receiving chronic methadone maintenance treatment (MMT) for addiction are closely monitored for signs of relapse. Urine drug screen (UDS) comprises a major component of ongoing patient assessment. As patients continue with MMT, developing medical conditions may necessitate addition of medications that interfere with UDS. Although widely accepted as masking agents, little guidance is available regarding management of patients receiving MMT with legitimate medical need for diuretics. The following describes a case in which furosemide clinically interfered with UDS interpretation for a patient receiving MMT. Potential management strategies are also discussed.