Ecdysterone is a phytosteroid widely discussed for its various pharmacological, growth-promoting, and anabolic effects, mediated by the activation of estrogen receptor beta (ERbeta). Performance-enhancement in sports was demonstrated recently, and ecdysterone was consequently included in the Monitoring Program, to detect potential patterns of misuse in sport. Only few studies on the pharmacokinetics of ecdysterone in humans have been reported so far. In this study, post-administration urine samples in twelve volunteers (single dose of 50 mg of ecdysterone) were analyzed using dilute-and-inject liquid-chromatography–tandem mass spectrometry. Identification and quantitation of ecdysterone and of two metabolites, 14-deoxy-ecdysterone and 14-deoxy-poststerone, was achieved. Ecdysterone was the most abundant analyte present in post-administration urine samples, detected for more than 2 days, with a maximum concentration (Cmax) in the 2.8–8.5 h urine (Cmax = 4.4–30.0 µg/mL). The metabolites 14-deoxy-ecdysterone and 14-deoxy-poststerone were detected later, reaching the maximum concentrations at 8.5–39.5 h (Cmax = 0.1–6.0 µg/mL) and 23.3–41.3 h (Cmax = 0.1–1.5 µg/mL), respectively. Sex-specific differences were not observed. Cumulative urinary excretion yielded average values of 18%, 2.3%, and 1.5% for ecdysterone, 14-deoxy-ecdysterone, and 14-deoxy-poststerone, respectively. Ecdysterone and 14-deoxy-ecdysterone were excreted following first-order kinetics with half-lives calculated with three hours, while pharmacokinetics of 14-deoxy-poststerone needs further evaluation.

Ecdysterone is a phytosteroid widely discussed for its various pharmacological, growth-promoting and anabolic effects mediated by activation of estrogen receptor beta (ERbeta). Performance-enhancement in sports was demonstrated recently, and ecdysterone was consequently included in the Monitoring Program to detect potential patterns of misuse in sport. Only few studies on the pharmacokinetics of ecdysterone in humans have been reported so far. In this study, post-administration urines in twelve volunteers (single dose of 50 mg of ecdysterone) were analyzed using dilute-and-inject liquid chromatography-tandem mass spectrometry. Identification and quantitation of ecdysterone and of two metabolites, 14-deoxy ecdysterone and 14-deoxy poststerone was achieved. Ecdysterone was the most abundant analyte present in post-administration urines, detected for more than 2 days with a maximum concentration (Cmax) in the 2.8-8.5 h urines (Cmax = 4.4-30.0 µg/mL). The metabolites 14-deoxy ecdysterone and 14-deoxy poststerone were detected later reaching the maximum concentrations at 8.5-39.5 h (Cmax = 0.1-6.0 µg/mL) and 23.3-41.3 h (Cmax = 0.1-1.5 µg/mL), respectively. Cumulative urinary excretion yielded average values of 18%, 2.3% and 1.5% for ecdysterone, 14-deoxy ecdysterone and 14-deoxy poststerone, respectively. Ecdysterone and 14-deoxy ecdysterone were excreted following first order kinetics with half-lives calculated with three hours, while pharmacokinetics of 14-deoxy poststerone needs further evaluation.