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BMJ Case Reports 2009; doi:10.1136/bcr.09.2008.0879
  • Reminder of important clinical lesson

Doxylamine toxicity: seizure, rhabdomyolysis and false positive urine drug screen for methadone

  1. Husnain Syed,
  2. Sumit Som,
  3. Nazia Khan,
  4. Wael Faltas
  1. Trinitas Hospital, Internal Medicine, 225 Williamson Ave, Elizabeth, New Jersey, 07207, USA
  1. Husnain Syed, husnainsyed{at}hotmail.com
  • Published 17 March 2009

Summary

The present report highlights the possible adverse effects of doxylamine, a common over the counter sleep aid. Doxylamine is an antihistamine that at toxic doses can cause anticholinergic effects, including seizures, rhabdomyolysis and death. The following case describes a patient with doxylamine toxicity who presented with seizure and confusion. Our patient was managed symptomatically, and remained otherwise stable throughout his hospitalisation. This case is atypical in terms of a delayed rhabdomyolysis and a false positive urine drug screen test for methadone. There is evidence that doxylamine at toxic levels can lead to false positives for methadone and phencyclidine testing using immunoassay-based urine drug screen kits. Urine drug screen testing on patients who are hospitalised is typically performed using immunoassays. However, in certain cases confirmatory secondary testing may be required. Doxylamine is prone to abuse and knowledge of the clinical presentation of its toxicity and the management of acute overdose can be life-saving.

Footnotes

  • Competing interests: None.

  • Patient consent: Patient/guardian consent was obtained for publication.

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