No abstract

Caffeine is a widely consumed psychostimulant with several mechanisms of action and various positive and negative effects on organisms. Caffeine undergoes extensive hepatic metabolism to form main metabolites such as theobromine, theophylline, paraxanthine, and 1,3,7-trimethyluric acid. However, interspecies diversities have been observed in caffeine metabolism. In the present study, we developed a sensitive and straightforward ultra-high-performance liquid chromatography-tandem mass spectrometry method to quantify caffeine and its primary metabolites, namely theobromine, theophylline, paraxanthine, and 1,3,7-trimethyluric acid in rat plasma. After extraction of analytes using micro solid-phase extraction plate, analytes were separated by elution gradient on the Acquity UPLC HSS T3 (50 × 2.1 mm, 1.8 μm) column over 4 min. The detection was done on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring modes using a positive electrospray ionization interface.The method was successfully validated according to the European Medicine Agency guideline over a concentration range of 5-1500 ng/ml for caffeine, 5-1200 ng/mL for theobromine, and 2.5-1200 ng/mL for theophylline, paraxanthine, and 1,3,7-trimethyluric acid. The developed method was applied to analyze samples from animal experiments focusing on the metabolism and effects of caffeine and caffeine-containing beverages.

Rationale Tuberculosis (TB) remains a challenging global infectious disease, mainly affecting the lungs. First‐line anti‐TB drugs play a crucial role in slowing down the rapid spread of TB. In addition, the patient might benefit from therapeutic drug monitoring since it has become an accepted clinical tool for optimizing TB treatment. Methods A simple and sensitive liquid chromatography/tandem mass spectrometry method was developed to monitor the plasma level of isoniazid, ethambutol and pyrazinamide in plasma samples. A one‐step extraction procedure using an Ostro™ plate was applied, and extracts were analyzed by gradient elution followed by detection on a mass spectrometer by multiple reaction monitoring mode. Results The analytes were separated within 4.2 min and over the concentration range of 0.2–10 μg/ml for isoniazid and ethambutol and 1–65 μg/ml for pyrazinamide. The method was successfully validated according to the European Medicine Agency guideline for the selectivity, linearity and lower limit of detection, precision and accuracy, matrix effect, extraction recovery, carryover, dilution integrity and stability, and applied for quantification of analytes in clinical samples from TB patients. Conclusions The presented method allows sensitive and reproducible determination of selected anti‐TB drugs with advantages such as low sample volume requirement, short run time of analysis, one‐step sample preparation procedure with capabilities for phospholipids removal, and a low quantification limit as well as a high degree of selectivity.

Highlights The Euro-American lineage 4.7 was the most represented among the XDR-TB/MDR-TB resistant strains. Seven of 12 isolates (58%) belonged to the same recent transmission chain. Strains originally from Eastern European countries were diagnosed in patients without any epidemiological links with these countries. Incidence of resistant XDR-TB/MDR-TB in Slovakia, while low, still should be taken to monitor.

Direct oral anticoagulants are widely used in many indications to prevent thromboembolic events. Routine therapeutic monitoring is not required; however, there is increasing evidence suggesting the benefit of plasma level measurement in some situations. In addition, laboratory monitoring might help improve patient and drug non‐compliance and thus individualize therapy. In the present study, we developed a sensitive and high throughput ultra‐high‐performance liquid chromatography‐tandem mass spectrometry method for simultaneous quantification of apixaban, dabigatran, edoxaban, and rivaroxaban in human plasma. A one‐step extraction procedure in 96‐well formate for phospholipid and protein removal was used for sample pre‐treatment, and analytes were separated using gradient elution over 4.2 min. Analytes were detected on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring mode. The method was validated according to the European Medicine Agency guideline for the selectivity, linearity, and lower limit of detection, precision and accuracy, matrix effects, extraction recovery, carryover, dilution integrity, and stability over a concentration range of 3.0–1000 ng/ml for all analytes. The validated method was applied to real clinical samples of patients treated with one of the drugs. Therefore, we can conclude that our method is suitable for therapeutic drug monitoring of direct oral anticoagulants.