Determination of higenamine and coclaurine levels in human urine after the administration of a throat lozenge containing Nandina domestica fruit

Higenamine is a key component of traditional Chinese herbal medicine. The fruit of Nandina domestica (which contains this component) is available as an ingredient in the so-called Nanten-nodo-ame throat lozenge found on the Japanese market, which is an over-the-counter pharmaceutical and is easy to purchase for Japanese athletes. However, higenamine is a non-selective β2-agonist, which is exemplified in the prohibited list of the World Anti-Doping Agency (WADA). Therefore, some have raised a concern regarding the potential cause of increased unintentional higenamine doping cases in the Asian region. This study aimed to investigate components of throat lozenges and develop a mass-spectrometry method for the quantification of higenamine and coclaurine in human urine. Moreover, a population study of Japanese subjects (n = 246) and an excretion study (n = 4) of the corresponding throat-lozenge recipients were performed to test the applicability of the current reporting threshold (i.e., 10 ng/mL) of higenamine set by WADA. The estimates of higenamine and coclaurine were 2.2 ± 0.1 μg/drop (mean of n = 12) and 0.5 ± 0.01 μg/drop (mean of n = 12), respectively. The maximum concentrations of higenamine and coclaurine were 0.2-0.4 and 0.3-1.0 ng/mL, respectively, at 10-12 h after administration of higenamine (nine drops); however, the concentrations in all four volunteers did not reach the positivity criterion of 10 ng/mL. No higenamine and coclaurine could be detected in the Japanese subjects. Therefore, there is no risk of detecting unintentional higenamine doping when the WADA reporting threshold is used.