LC-MS/MS method for rapid and accurate detection of caffeine in a suspected overdose case

Excessive intake of caffeine, otherwise known to be a safe and mild central nervous system stimulant, causes nausea, vomiting, convulsions, tachycardia, and eventually fatal arrhythmias and death. Caffeine intoxication, a global problem, has been increasing in Japan since 2013. Thus, there is a need for rapid and accurate diagnosis of caffeine poisoning in forensic and clinical toxicology investigations. Herein, we demonstrate rapid and accurate caffeine quantitation by liquid chromatography tandem mass spectrometry using the standard addition method in a fatal case. Biological samples were diluted 500–100,000-fold and subjected to a simple pretreatment (adding caffeine standard and internal standard and passing through a lipid removal cartridge). The multiple reaction monitoring transitions were 195 → 138 for quantitation, 195 → 110 for the qualifier ion, and 204 → 144 for the internal standard (caffeine-d9). The standard plots were linear over 0–900 ng/mL (r² = 0.9994–0.9999) for biological samples, and the reproducibility (%RSD) of the method was 1.53–6.97% (intraday) and 1.59–10.4% (interday). Fatal levels of caffeine (332 μg/mL) and toxic to fatal levels of olanzapine (625 ng/mL), along with other pharmaceuticals were detected in the external iliac venous blood. The cause of death was determined to be multi-drug poisoning, predominantly caused by caffeine. Our method is useful for not only forensic cases but also the rapid diagnosis of caffeine overdose in emergency clinical settings.