SOFT 2004 Meeting Abstracts - Society of Forensic Toxicologists

P59
INTERPRETING ANTIHISTAMINE LEVELS IN POST~MORTEM BLOOD; ESTABLISHING
INCIDENTAL AND CONTRIBUTORY RANGES FOR EVALUATION PURPOSES
Michelle Sandberg *, Dan Anderson, and Kristina Fritz
Los Angeles County Department ofCoroner, Los Angeles, CA
Over the last ten years, the Food and Drug Administration has approved numerous prescription
antihistamines safe for over~the~counter (OTC) distribution. Antihistamines are a broad class of drugs,
frequently taken to offer symptomatic relief from colds, sinus congestion, allergies, and are also a class of
drugs frequently abused.
In forensic toxicology, post~mortem (PM) redistribution of drugs complicates the interpretation of results.
Many of the reference materials available are for clinical interpretation, and extrapolating PM levels for
comparison to clinical values is not ideal. The substantial volume of casework at the Los Angeles County
Department of Coroner (LACDOC) Laboratory provided us the ability to establish applicable PM blood
level ranges for interpretation ofthe first generation antihistamines by a query of the LACDOC toxicology
database over a three-year period. First generation antihistamines are easily detected using a basic liquidliquid
extraction with an acidic back extraction. Diphenhydramine, chlorpheniramine, doxylamine,
promethazine, and hydroxyzine are commonly detected at the LACDOC by GCINPD.
A brief summary ofthe query results and interpretation are as follows:
Categories
Published
Clinical
Therapeutic
Drug Levels
Post Mortem Central Blood Levels, mgIL
Diphenhydramine Doxylamine Promethazine Hydroxyzine Chlorpheniramine
(471 cases) (87 cases) (136 cases) (44 cases) (126 cases)
-0.11 -0.10 -0.08 -0.02
- 0.14
Determined
om 0.70 0.01- 0.70 0.01- 0.30 0.01 0.50 om 0.30
"Incidental"
81% (383) 84% (73) 74% (101) 73% (32) 96% (I21)
Drug Levels
0.31 - 0.0.90 0.51-1.1
Determined
16% (21) 18% (8)
"contributory" >0.70 > 0.70
>0.30
and
and
. to the cause of 17% (80) 15% (1) 4%(5)
>0.90 >1.1
death
10%(14) 9%(4)
Determined as
the > 19 > l32
"sole cause 2%(8) 1%(1) -- -- --
of death"
The query results were categorized as follows:
• Incidental - Levels that represent over 70% of the quantitated cases for a particular drug, and
correspond to therapeutic dosing
• Contributory - Levels that were greater than therapeutic and could not be ruled out as a
contributing cause ofdeath
• Sole Cause ofDeath - Due to the drug alone, not influenced by any other drug
This study determined PM therapeutic central blood levels for five, first-generation antihistamines and
central blood values that indicated the drug was a contributing factor in the cause of death. The Los
Angeles County Coroner Laboratory continues to evaluate the cases where levels are greater than the
"contributing" category and may have been the sole cause ofdeath, ifother weren't drugs present.
Keywords: Antihistamines, Interpretation, Post-mortem blood levels
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