Method for determination of cytisine in post-mortem biological matrices and its application to two forensic cases

Cytisine is the active ingredient in preparations used for smoking cessation. Its popularity is attributed to its low cost, efficacy, and low incidence of adverse effects. Additionally, its easy over-the-counter availability is also significant. This accessibility makes it a potential substance for use in suicidal attempts. The aim of this study was to develop a method for the determination of cytisine in biological material for use in clinical and forensic toxicology, and to apply this method in authentic cases.

Biological samples were subjected to liquid-liquid extraction using cytisine-d₄ as an internal standard. Analyses were performed using a Hydrophilic Interaction Liquid Chromatography (HILIC) column with the technique of ultra-high-performance liquid chromatography coupled with triple quadrupole tandem mass spectrometry.

For both matrices (blood and urine), the linear concentration range was 5-1000 ng/mL. The method met all validation requirements. The concentration of cytisine in a man taking it for smoking cessation in post-mortem materials was 21.4 ng/mL in blood, 958.9 ng/mL in urine, ca. 30 ng/mL in vitreous humor, and ca. 40 ng/mL in bile. In contrast, for a man with cytisine intoxication, the concentration was 174.6 ng/mL in blood and > 10,000 ng/mL in urine. In both cases, no N-methylcytisine was detected.

The developed method can be used for the determination of cytisine in post-mortem biological matrices as well as for clinical purpose. We presented the concentrations of cytisine in the post-mortem biological samples of a man taking cytisine for smoking cessation and of a man with suicidal cytisine poisoning.