Hair analysis to discriminate voluntary doping vs inadvertent ingestion of the aromatase inhibitor letrozole

AbstractLetrozole is an aromatase inhibitor, used to treat post ‐menopausal women with hormone receptor‐positive or unknown advanced breast cancer. It is prohibited in sport because it is used together with androgen anabolizing steroids to avoid their adverse effects. In case of adverse analytical finding, it may be important to distinguish between repetitiv e use due to voluntary administration and occasional use, possibly due to involuntary intake. With the objective to identify the dose capable of producing a positive hair testing, and to apply these results to the scenarios of letrozole inadvertent ingestion by an athlete, this study aims at investi gating the urinary excretion and incorporation into hair of single doses of letrozole.Seven subjects were recruited for an excretion study of letrozole and its metabolite bis(4 ‐cyanophenyl) methanol (M1) in urine, after the consumption of 0.62 mg, 1.25 mg, and 2.5 mg of letrozole, and to investigate the incorporation in hair after ingestion of 0.62 mg and 2.5 mg of letrozole. Urine and hair samples were also obtained from two women in chronic therapy.Urinary concentrations of letrozole and its metabolite M1 were lower in subjects administered once with 0.62 mg, 1.25 mg or 2.5 mg letrozole than in women in regular therapy with 2.5 mg/day. In hair collected after single dosage, concentrations of 16 ‐60 pg/mg were detected while in women in chronic therapy concentrations were higher than 160 pg/mg all along the hair shaf...
Source: Drug Testing and Analysis - Category: Drugs & Pharmacology Authors: Tags: RESEARCH ARTICLE Source Type: research