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LC-MS/MS Quantification of Five Antihistamines in Antemortem Blood: Method Validation and Application
Kenson Jean1, Kristin W Kahl1, Lisa J Reidy1
1Department of Pathology and Laboratory Medicine, Toxicology Laboratory, University of Miami Miller School of Medicine, Rosenstiel Medical Science Building, 1600 NW 10th Ave, 7th Floor, Suite 7025A, Miami, FL 33136 USA.
Journal of Analytical Toxicology
|August 13, 2026
Summary
A new LC-MS/MS method accurately quantifies five first-generation H1 antihistamines. This validated method is crucial for forensic casework involving driving under the influence of drugs (DUID) and drug-facilitated crimes (DFC).
Area of Science:
- Forensic Toxicology
- Analytical Chemistry
Background:
- First-generation H1 antihistamines cause central nervous system effects like sedation and cognitive impairment.
- These antihistamines present risks in driving under the influence of drugs (DUID) and drug-facilitated crimes (DFC) investigations.
Purpose of the Study:
- To develop and validate a sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method.
- To quantify five common first-generation H1 antihistamines: chlorpheniramine, diphenhydramine, doxylamine, hydroxyzine, and promethazine.
Main Methods:
- A validated LC-MS/MS method was employed.
- The method utilized a 1/x linear calibration model with a range of 1-200 ng/mL.
- Limit of detection was 0.5 ng/mL for all compounds, with acceptable bias, precision, and stability.
Main Results:
- The method demonstrated acceptable performance characteristics, including sensitivity and specificity.
- Analysis of authentic forensic specimens revealed a wide concentration range for diphenhydramine in DUID and DFC cases.
- The method proved stable for 24 hours post-injection.
Conclusions:
- The validated LC-MS/MS method is suitable for the reliable quantification of first-generation H1 antihistamines in forensic samples.
- This method is essential for accurate assessment in human-performance casework, particularly in complex DUID and DFC investigations involving polysubstance use.
