Ofloxacin causes false-positive immunoassay results for urine opiates

Immunoassay drug screening tests are usually used as a control during methadone maintenance programmes, to check cleanliness of drugs during detoxification treatment and abstinence programmes. False-positive results can have catastrophic consequences for the patient, as shown in the case report. False-positive results were reported for opioids following ofloxacin or rifampicin and for LSD following mucolytic. Since inpatient and outpatient units usually employ an urine quick test (immunoassay), positive results should be checked with gas chromatography/mass spectroscopy (GC-MS) or high pressure liquid chromatography (HPLC) before conclusions from the positive urine screening results can be drawn.