Hyperprolactinemia is associated with D2 occupancy in which range?

• A. 10-30%
• B. 50-75%
• C. 78%
• D. 80-95%

Answer: (B)

Prolactin secretion from the pituitary is normally kept in check by dopamine acting on D2 receptors. When an antipsychotic blocks these receptors, the degree of D2 receptor occupancy in the tuberoinfundibular pathway determines how much prolactin rises. Hyperprolactinemia is most consistently seen when D2 occupancy is in the mid-range, about 50-75%. At this level, dopaminergic inhibition is sufficiently reduced to release prolactin, but occupancy is not so high as to produce the most severe motor side effects yet. Lower occupancy tends not to elevate prolactin significantly, while very high occupancy increases the risk of extrapyramidal symptoms as well as prolactin elevation.