Hair analysis for the detection and quantification of letrozole after single and repeated use

Letrozole is an aromatase inhibitor, used to treat post-menopausal women with hormone receptor-positive or 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 repetitive 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, this study aims at investigating the incorporation into hair of single or repeated doses of letrozole.