Lomerizine Hydrochloride

Lomerizine (LMZ) is an antimigraine drug that works as a calcium channel blocker and has selective effects on the central nervous system. It is metabolized into trimetazidine (TMZ), which is a prohibited substance owing to its performance‐enhancing effects in both human and animal sports. Effective doping control measures are imperative to distinguish the source of TMZ in samples to ensure integrity and fairness of the sport, therefore a comprehensive analysis of LMZ metabolites is essential to identify potential biomarkers in camel urine for effective doping control.

Camel urine samples were collected from four healthy animals following a single oral administration of LMZ at a dosage of 1 mg/kg body weight. In vitro studies were conducted using homogenized camel liver samples. Lomerizine and its metabolites were extracted using solid‐phase extraction and analyzed with a Thermo Fisher Orbitrap Exploris liquid chromatography mass spectrometry system. The acquired data was processed with the Compound Discoverer software.

The study conducted a comprehensive analysis of LMZ metabolites in camels and identified 10 phase I and one phase II metabolites. The primary pathway for the formation of phase I metabolites was de‐alkylation, while phase II metabolite was formed through alkylation of the parent drug. The study provided valuable insights into the unique metabolic pathways of LMZ in camels under specific experimental conditions.

The developed method enables the detection and characterization of LMZ and its metabolites in camels. The identified metabolites has the potential to act as marker metabolites for the distinctive detection of LMZ in camel urine to ensure efficient analytical strategies for routine doping control applications.

Dried blood spot (DBS) analysis has been an inherent part of sports drug testing through the technological advancements of the past decade. Trimetazidine, a non‐threshold banned substance, is excreted into urine after a dose of the permitted drug lomerizine. Therefore, a lomerizine‐specific metabolite (M6) is analyzed to confirm the origin of trimetazidine in traditional urine analysis. Application studies were conducted to develop an analytical method for trimetazidine applicable to DBS. These studies comprise (1) the effect of different sampling sites on the detection of trimetazidine, (2) the determination of the appropriate trimetazidine level required for DBS analysis, and (3) differentiating between trimetazidine and lomerizine use. A high‐resolution mass spectrometric method for detecting trimetazidine in DBS was validated. After oral administration of trimetazidine (n = 7), venous and capillary blood (fingertip and upper arm) were spotted on cellulose paper. Trimetazidine could be identified in DBS in all subjects up to 60 h after administration. The limit of detection was 0.05 ng/ml, and the limit of identification was 0.06 ng/ml, suggesting the minimum required performance level of 0.2 ng/ml. In the fingertip capillary blood, biases of 9.7% (vs. upper arm) and 13.0% (vs. vein) were observed in the trimetazidine intensity; however, there were no concerns in the qualitative analysis. After administering lomerizine (n = 10), the intact lomerizine has a strong peak intensity in blood compared to trimetazidine. Contrary to urine analysis, the M6 was less detectable in blood. Laboratories should confirm intact lomerizine whenever trimetazidine is identified in DBS.