Comparison of urinary excretion patterns among exposures to cosmetic preservative, herbicide, and nootropic stimulant in anti-doping analysis

Abstract

Doping with meclofenoxate, a nootropic stimulant prohibited in-competition by the World Anti-Doping Agency (WADA), is identified through the primary marker of urinary 4-chlorophenoxyacetic acid (4-CPA). However, the presence of 4-CPA can also arise from permissible sources. This study ventured into comparing urinary excretion patterns among exposures to permitted chemicals (chlorphenesin and 4-CPA) and the banned stimulant (meclofenoxate) and interpreting the analytical findings according to the reporting requirements. A validated method, utilising direct injection and ultra-performance liquid chromatography-tandem mass spectrometry, was employed for urine analysis. In the first experiment, participants applied chlorphenesin-containing cosmetics with varied functions, dosages, frequencies, and application sites. Sunscreen usage led to significantly higher urinary 4-CPA concentrations (up to 1049 ng/mL) as compared to others, highlighting the impact of cosmetic formulation composition for chlorphenesin delivery. The diagnostic marker for preservative exposure included 3-(4-chlorophenoxy)-2-hydroxypropanoic acid (4-CPP) and chlorphenesin and its conjugated metabolites, with 4-CPP reaching higher concentrations (C_max of 903-7629 ng/mL) and for a longer period, up to 7-14 days. In the second experiment involving meclofenoxate supplement administration, urinary C_max levels of 4-CPA were observed between 36,287 and 39,769 ng/mL at 3-10 h post-dosing, with the parent meclofenoxate undetected in all participants' samples. The third experiment, focused on occupational herbicide exposure in agricultural environments, detected minimal 4-CPA (< 10 ng/mL) in urine. WADA's current guidance for meclofenoxate aligns with reporting correct analytical results. Investigations, such as the experimental approach herein, offer valuable evidence addressing accuracy concerns in anti-doping tests, contributing insights for future amendments.

Keywords: 4-Chlorophenoxyacetic acid; Centrophenoxine; Chlorphenesin; Meclofenoxate; Sports drug testing; World Anti-Doping Agency.