PRL and hyperprolactinemia: Some of the current antipsychotics cause hyperprolactinemia owing to their D2 receptor antagonism in the pituitary gland.9, 36 TAK‐063 does not cause hyperprolactinemia in rats as PDE10A expression is low in the pituitary gland.13, 39 Thus, combination of TAK‐063 with haloperidol at subeffective doses did not exacerbate the effects on plasma prolactin in rats.