Bromocriptine has an ergot alkaloid structure. Ergot alkaloids are divided into 2 groups; amino acid ergot alkaloids and amine ergot alkaloids, bromocriptine is part of the former group. It contains a bromine halogen on the ergot structure which increases the affinity for the D2-receptor but often reduces the efficacy. The similarity between the dopamine structure and the ergoline ring in bromocriptine is likely the cause for its action on the dopamine receptors. It has shown to have equal affinity for D2- and D3-receptor and much lower affinity for D1-receptor.