Quetiapine cross-reactivity among three tricyclic antidepressant immunoassays

Robert G. Hendrickson, Anthony P. Morocco

Research output: Contribution to journalArticlepeer-review

32 Scopus citations


Quetiapine is an atypical antipsychotic agent with structural similarities to the tricyclic antidepressants (TCA). We report a case of quetiapine overdose that was initially clinically similar to that of a TCA overdose and caused a false-positive TCA immunoassay. We then analyzed three common TCA immunoassays [Microgenics (formerly Diagnostic Reagents, Inc.) Tricyclics Serum Tox EIA Assay, Syva® RapidTest d.a.u.®, and Biosite Triage® Panel for Drugs of Abuse] with quetiapine in solution as well as urine from both an overdose patient and a therapeutic patient. There was significant variation of the cutoff of false-positivity in all three immunoassays. Both the Syva® and Microgenics® immunoassays tested positive in both the overdose and therapeutic samples and were positive at urine levels of 100 μg/mL and 10 μg/mL, respectively. The Triage® immunoassay was negative in solutions up to 1000 μg/mL and negative in both the therapeutic and overdose urine samples. Quetiapine may cause false-positive TCA immunoassay with both therapeutic use and in overdose. Significant variation exists between immunoassays to detect quetiapine as a false-positive test.

Original languageEnglish (US)
Pages (from-to)105-108
Number of pages4
JournalJournal of Toxicology - Clinical Toxicology
Issue number2
StatePublished - May 8 2003


  • False-positive
  • Overdose
  • Quetiapine
  • Tricyclic antidepressants
  • Urine tests

ASJC Scopus subject areas

  • Toxicology
  • Health, Toxicology and Mutagenesis


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