Bromocriptine reduces the level of the hormone prolactin by affecting the pituitary gland. It is sometimes used to treat conditions in which there is too much prolactin, such as certain forms of PMS and infertility.
The herb chasteberry inhibits prolactin secretion and might have unpredictable effects if combined with bromocriptine. 1–4
References
REF1 Milewicz A, et al. Vitex agnus-castus extract in the treatment of luteal phase defects due to latent hyperprolactinemia. Results of a randomized placebo-controlled double-blind study. Arzneimittelforschung 43(7): 752–756, 1993.
REF2 Jarry H, et al. In vitro prolactin but not LH and FSH release is inhibited by compounds in extracts of Agnus-castus: Direct evidence for a dopaminergic principle by the dopamine receptor assay. EYP Clin Endocrinol 102: 448–454, 1994.
REF3 Sliutz G, et al. Agnus-castus extracts inhibit prolactin secretion of rat pituitary cells. Horm Metab Res 25(5): 253–255, 1993.
REF4 Schulz V, et al. Rational phytotherapy. New York: Springer-Verlag, 1998: 241–242.