SOFT 2004 Meeting Abstracts - Society of Forensic Toxicologists

P8
A CASE OF FATAL OVERDOSE WITH LABETALOL
Karen Woodall"', Centre of Forensic Sciences, Toxicology Section, 25 Grosvenor Street, Toronto, Ontario,
Canada
Labetalol (Normodyne®, Trandate®) is an alpha and beta-adrenergic and beta-adrenergic receptor
antagonist used in the treatment of hypertension. A typical dose oflabetalol ranges from 200 400 mg/day
however some individuals may require up to 2100 mg/day. Symptoms of labetalol overdose are excessive
hypotension and bradycardia. There is very limited information available regarding labetalol concentrations
and toxicity and no reports where the cause of death has been attributed solely to a labetalol overdose. This
study describes a case where the cause ofdeath was attributed to an acute overdose of labetalol.
A 79-year-old female was admitted to hospital for high blood pressure and chest pain. She was stabilized
and after remaining in hospital for 7 days was being prepared for discharge. At this time she was observed
to have swallowed numerous tablets by another patient. She subsequently became hypotensive and
bradycardic, and resuscitation attempts were unsuccessful. A blood sample taken during the attempted
resuscitation was tested at the hospital and the drug screen showed that labetalol was significantly higher
than the therapeutic range. Empty prescription bottles of labetalol, lorazepam and furosemide (medications
she brought with her to the hospital) were found at the scene, however the actual number of tablets taken is
not known. There were no other significant findings in the hospital drug screen except for the elevated
labetalol concentration.
A postmortem was conducted and toxicology testing was performed on a heart blood sample. Labetalol was
measured by high-pressure liquid chromatography (HPLC) and the detected concentration was 15 mg/L.
Lorazepam was measured by mass spectrometry (MS) and was detected at a concentration of 73 ng/mL. In
addition to specific testing for labetalol and lorazepam, a general basic drug screen using gas
chromatography and mass spectrometry (GC and GCIMS) was performed and traces of sertraline and
metoprolol were detected. This laboratory does not have a method for the analysis of furosemide.
Therapeutic concentrations of labetalol in serum have been shown to range from 0.02 - 0.25 mg/L, and
levels over 0.5 mg/L are considered to be toxic. In one case report, a woman who suffered renal failure
following an acute ingestion of labetalol (16g) had a serum concentration of 29 mg/mL. The concentration
of labetalol in this case is approximately 60 times higher than the therapeutic levels. The autopsy showed
signs of chronic hypertension but no gross or microscopic cause of death. In the absence of other
significant drug findings the cause ofdeath was reported as acute labetalol intoxication.
Key words: labetalol, fatality, overdose
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