Tetrahydropalmatine (THP) is an alkaloid found in several different plant species, mainly in the Corydalis genus (Yan Hu Suo), but also in other plants such as Stephania rotunda. These plants have traditional uses in Chinese herbal medicine. The pharmaceutical industry has synthetically produced the more potent enantiomer Levo-tetrahydropalmatine (Levo-THP), which has been marketed worldwide under different brand names as an alternative to anxiolytic and sedative drugs of the benzodiazepine group and analgesics such as opiates. It is also sold as a dietary supplement.