False-positive Fentanyl Urine Detection after Initiation of Labetalol Treatment for Hypertension in Pregnancy: A Case Report.

ABSTRACT

BACKGROUND: Labetalol hydrochloride (LH) is a pharmacologic treatment for hypertensive disease (HD) in pregnancy. However, for pregnant persons with substance use disorders (SUDs), LH may interfere with urine drug testing. CASE SUMMARY: We present 3 pregnant or postpregnant persons with SUDs who experienced presumptive positive urine immunoassays for fentanyl while prescribed LH for perinatal HD. DISCUSSION: Labetalol hydrochloride treatment for HD in pregnancy can result in presumptive positive urine immunoassays for fentanyl. Unrecognized or misinterpreted, this phenomenon can lead to significant consequences for pregnant and postpartum persons with co-occurring substance use and hypertensive disorders. Clinicians caring for pregnant persons with SUDs must be aware of this phenomenon and its sequelae when ordering and interpreting urine immunoassays for fentanyl.