False-positive ODA testing results due to prescription medications .

M any over-the-counter, or OTC, medicines containing pseudoephedrine, ephedrine, or other sympathomimetic amines interfere with screening tests for amphetamines but do not cause positive test results in the gas chromatography/ mass spectrometric, or GC/MS, confirmation, thus pose no serious challenge in drugs-of-abuse (DOA) testing. In contrast, several prescription medicines containing opioid, amphetamines, or other ingredients can cause positive confirmed results in DOA testing. Use of Marinol to control severe pain produces a positive confirmatory test for marijuana metabolite (11-nor-9-carboxy-Δ 9-tetrahydrocannabinol; THC-COOH) in urine. Although the presence of benzodiazepines in urine is not always tested in federal workplace drug testing (five Substance Abuse and Mental Health Services Administration, or SAMHSA, drugs are amphetamines, cocaine as benzoylecgonine, opiates, marijuana as THC-COOH, and phencyclidine), private employers may test for benzodiazepines in a drugs-of-abuse panel. It is important for an individual undergoing workplace drug testing to report the use of such prescription medication and name of the prescribing physician so the Medical Review Officer can contact the physician and verify medical use of such controlled substances. Otherwise, employment may be denied or other adverse action may be taken by the employer against that individual. Interference with amphetamine/methamphetamine tests Some prescription medications contain amphetamine or meth-amphetamine, while the active ingredient of some prescription medication may be metabolized to amphetamine or metham-phetamine, causing positive amphetamine/methamphetamine test results (see Table 1). 1 For example, Adderall contains a mixed amphetamine salt widely prescribed as a psychostimulant medication for attention deficit hyperactive disorder, or ADHD, and use of such medication would cause a positive amphetamine test. In January 2002, the U.S. Food and Drug Administration approved Paremyd eye drops which contain hydroxyamphet-amine and tropicamide. Although amphetamine is metabolized to hydroxyamphetamine, hydroxyamphetamine is not metabo-lized to amphetamine. Therefore, use of such products should not cause a positive amphetamine test result. Several prescription medications for pain management contain morphine, codeine, hydrocodone, oxycodone, or related opioid. Oxycodone has variable cross-reactivity with different opiate-screening assays, and there is also a specific immunoassay which recognizes the presence of oxycodone in urine — but taking codeine or morphine containing analgesic medication produces positive opiate test results in drugs-of-abuse testing. Ingestion of fentanyl-containing drugs (which are also opioid) or use of the Duragesic fentanyl patch should not cause a positive opiate test because fentanyl has very poor cross-reactivity against antibodies used in opiate-screening assays, which recognize morphine and related substances only. Although marijuana is a Schedule …