title: The effect of thioridazine on the Automatic Clinical Analyzer serum tricyclic anti-depressant screen.
abstract: A patient who had ingested thioridazine and flurazepam was brought to the authors' emergency department. Initial laboratory evaluation included a positive result for a serum screening test for tricyclic anti-depressants performed with the DuPont Automatic Clinical Analyzer. This false positive test result caused considerable unnecessary treatment and expense for the patient. The authors have found that a serum thioridazine concentration of 125 ng/mL (within the usual therapeutic range for this drug) will produce a false positive automatic clinical analyzer serum tricyclic anti-depressant screen result. Because thioridazine is the most widely used phenothiazine and is prescribed more frequently than the most widely used tricyclic anti-depressant, it is important to recognize this cause of a false positive result.
mesh_terms: D000929:Antidepressive Agents, Tricyclic / Q000097:blood* / Q000506:poisoning; D001322:Autoanalysis / Q000295:instrumentation*; D001774:Blood Chemical Analysis / Q000295:instrumentation*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008875:Middle Aged; D013881:Thioridazine / Q000097:blood* / Q000506:poisoning
chemical_list: D000929:Antidepressive Agents, Tricyclic; D013881:Thioridazine