UMEM Educational Pearls

Category: Toxicology

Title: Urine Drug Screens

Keywords: drug abuse, urine drug screen, cocaine (PubMed Search)

Posted: 7/14/2007 by Fermin Barrueto, MD (Emailed: 7/8/2007) (Updated: 2/18/2020)
Click here to contact Fermin Barrueto, MD

Urine Drug Screens Though we order them often, be sure you know what your results mean: Cannabinoids: an accurate test though clinically not important information, positive for 5 days to a full month with chronic users. Cocaine: the most accurate and precise test, positive for 3-5 days. Amphetamine: the most imprecise with many false positives and false negatives. Cough/cold preparations that contain pseudephedrine, phenylephrine or other decongestants can turn it falsely positive. BDZ: only benzodiazepines that are metabolized to oxazepam will turn positive. You can see false negatives with alprazolam and even lorazepam. Opioids: Semisynthetics like oxycodone and hydrocodone may give false negatives at low levels. This screen will NOT catch methadone, meperidine, fentanyl, propoxyphene, tramadol. PCP: False positives from dextromethorphan and ketamine