Purpose: To establish a UPLC-MS/MS method for the simultaneous determination of chlorpheniramine (CPM) and its metabolites, desmethylchlorpheniramine (DCPM) and didesmethylchlorpheniramine (DDCPM), in blood and saliva, and to evaluate the feasibility of using saliva as an alternative biological matrix for CPM exposure assessment.

Methods: A UPLC-MS/MS method was established for the simultaneous determination of CPM, DCPM, and DDCPM in blood and saliva. Mobile phase A consisted of water and mobile phase B consisted of acetonitrile. After comparing eight extraction solvents, dichloromethane–acetonitrile (1:1, v/v) was selected for liquid–liquid extraction. An aliquot of 0.1 mL of sample was mixed with internal standard and extraction solvent, vortexed, and centrifuged. The supernatant was filtered, and 5 μL was injected for analysis. Six healthy volunteers received a single oral dose of 8 mg CPM capsules. Blood and saliva samples were collected simultaneously at predetermined time points after administration, and saliva sampling continued until 18 days after the initial 48 h period. Pearson correlation analysis was performed using SPSS 27.0 (α = 0.05), the saliva-to-blood concentration ratio (S/P) was directly calculated, and pharmacokinetic parameters were calculated using DAS 2.0 software.

Results: The established UPLC-MS/MS method enabled simultaneous qualitative and quantitative analysis of CPM and its metabolites in blood and saliva, with method validation results meeting all acceptance criteria. After a single oral dose of 8 mg CPM, the elimination half-life (t₁/₂) of CPM in saliva was (81.4 ± 21.9) h and the time to peak concentration (Tₘₐₓ) was (5.06 ± 1.82) h; in blood, t₁/₂ was (35.8 ± 17.4) h and Tₘₐₓ was (2.13 ± 0.58) h. For DCPM, t₁/₂ in saliva was (54.3 ± 43.0) h and Tₘₐₓ was (52.8 ± 9.60) h; in blood, t₁/₂ was (19.0 ± 5.54) h and Tₘₐₓ was (48.12 ± 1.62) h. The concentration range of DDCPM was 1.02–2.86 ng/mL in blood and 1.00–1.53 ng/mL in saliva. CPM concentrations in saliva and blood showed a positive correlation across all time points (r = 0.848 ± 0.09, P < 0.05), and the concentration–time profiles also demonstrated a significant positive correlation (r = 0.778 ± 0.091, P < 0.05). The S/P ratio was 2.38 ± 0.98.

Conclusions: This study systematically elucidates, for the first time, the pharmacokinetic characteristics of CPM and its metabolites in saliva, demonstrating a strong positive correlation between salivary and blood CPM concentrations and a longer detection window in saliva. Saliva can serve as a non-invasive alternative matrix for CPM exposure assessment, providing a new technical approach and scientific basis for poisoning diagnosis in children and adults, therapeutic drug monitoring, and forensic toxicology analysis.