agnus castus
an herbal preparation derived from the flowers of the chasteberry tree and approved in Germany for use in the management of symptoms associated with the late luteal phase of the menstrual cycle (see premenstrual dysphoric disorder) and in the alleviation of menstrual cycle abnormalities or irregularities. Although its active components and mechanism of action are unknown, agnus castus has been shown to possess significant estrogenic activity and is thought to act upon the pituitary gland. Agnus castus may also possess dopaminergic activity, and thus its concurrent use with either dopamine-receptor agonists or dopamine-receptor antagonists is not recommended, given the potential interactions that may occur. Side effects of agnus castus use are rare but may include rashes and itching, nausea and vomiting, dizziness, headache, drowsiness, and confusion. Also called vitex agnus castus.