Common herbal supplements did not produce false-positive results on urine drug screens analyzed by enzyme immunoassay.

The use of the urine drug screen (UDS) to test for substances of abuse has become commonplace because urine is relatively easily obtained and concentrations of drug in urine tend to be higher than in other biological matrices (1). The UDS is increasingly utilized as a pre-employment requirement, toxicological screen in the emergency room, as part of a general admissions medical screen at inpatient psychiatric facilities, and as a measure of abstinence in patients being treated at substance abuse facilities (2). Also, members of the armed services and athletes are subject to periodic or random screens. Additionally, "off site" diagnostic kits are increasingly being utilized. Positive results are highly suggestive that an individual has been using the substance in question. The major UDS test methods used in the U.S. are automated immunoassay tests such as radioimmunoassay (RIA), fluorescence polarization immunoassay (FPIA), and enzyme immunoassay (EIA) (2). It has been recognized that a number of medications (2,3), certain foods (4), and herbal products (5) may cross-react and/or produce "false-positive" results for a number of analytes. The use of herbal supplements has expanded dramatically in the last decade and as part of our ongoing herb-drug interaction studies we sought to determine their potential to confound the results of the UDS. Accordingly, we assessed normal volunteers participating in a series of studies for the potential of commonly utilized herbal preparations to produce "false positive" results during formal study. Normal healthy volunteers who had provided written informed consent participating in studies to assess herb-drug interactions received a baseline morning UDS by an EIA method (Synchron LX ~ Systems, Beckman Coulter, Inc.) at the intitiation of the study following an overnight stay on our General Clinical Research Center (GCRC) while receiving no medications. The UDS was repeated again after an overnight visit at our GCRC after 14 days of treatment with a standardized herbal preparation. All herbal products used in the studies were analyzed for representative phytochemical contents (Table l). The UDS utilized in our studies included screens for amphetamine, barbiturates, benzodiazepines, cocaine, opiates, phencyclidine, and cannabinoids. Compliance with herbal treatment was reinforced by dispensing tablets or capsules in blister-packs or "medication minders" and performing follow up counts as previously described (6). Positive UDS results were followed by confirmatory testing on the urine specimen. Herbal products assessed included eight of the most commonly consumed herbal supplements in the U.S. (Table I). Subjects (n = 90) …