title: The trazodone metabolite meta-chlorophenylpiperazine can cause false-positive urine amphetamine immunoassay results.
abstract: Amphetamines and methamphetamines are part of an important class of drugs included in most urine drugs of abuse screening panels, and a common assay to detect these drugs is the Amphetamines II immunoassay (Roche Diagnostics). To demonstrate that meta-chlorophenylpiperazine (m-CPP), a trazodone metabolite, cross-reacts in the Amphetamines II assay, we tested reference standards of m-CPP at various concentrations (200 to 20,000 g/L). We also tested real patient urine samples containing m-CPP (detected and quantified by HPLC) with no detectable amphetamine, methamphetamine, or MDMA (demonstrated by GC MS). In both the m-CPP standards and the patient urine samples, we found a strong association between m-CPP concentration and Amphetamines II immunoreactivity (r = 0.990 for the urine samples). Further, we found that patients taking trazodone can produce urine with sufficient m-CPP to result in false-positive Amphetamines II results. At our institution, false-positive amphetamine results occur not infrequently in patients taking trazodone with at least 8 trazodone-associated false-positive results during a single 26-day period. Laboratories should remain cognizant of this interference when interpreting results of this assay.
authors: Department of Pathology, Massachusetts General Hospital, Boston, MA 02114, USA. jmbaron@partners.org
authors: Jason M
authors: JM
authors: Baron
authors: David A
authors: DA
authors: Griggs
authors: Andrea L
authors: AL
authors: Nixon
authors: William H
authors: WH
authors: Long
authors: James G
authors: JG
authors: Flood
mesh_terms: D000661:Amphetamine / Q000097:blood / Q000652:urine*; D014151:Anti-Anxiety Agents / Q000097:blood / Q000652:urine*; D005189:False Positive Reactions; D006801:Humans; D007118:Immunoassay; D010879:Piperazines / Q000592:standards / Q000652:urine*; D015813:Substance Abuse Detection; D019966:Substance-Related Disorders / Q000097:blood / Q000652:urine; D014196:Trazodone / Q000097:blood / Q000652:urine*
chemical_list: D014151:Anti-Anxiety Agents; D010879:Piperazines; D000661:Amphetamine; C015068:1-(3-chlorophenyl)piperazine; D014196:Trazodone