Like other drugs that antagonize dopamine D 2receptors, paliperidone elevates prolactin levels and the elevation persists during chronic administration. Paliperidone has a prolactin-elevating effect similar to that seen with risperidone, a drug that is associated with higher levels of prolactin than other antipsychotic drugs. 

Hyperprolactinemia, regardless of etiology, may suppress hypothalamic GnRH, resulting in reduced pituitary gonadotrophin secretion. This, in turn, may inhibit reproductive function by impairing gonadal steroidogenesis in both female and male patients. Galactorrhea, amenorrhea, gynecomastia, and impotence have been reported in patients receiving prolactin-elevating compounds. Long-standing hyperprolactinemia when associated with hypogonadism may lead to decreased bone density in both female and male subjects.

Tissue culture experiments indicate that approximately one-third of human breast cancers are prolactin dependent in vitro, a factor of potential importance if the prescription of these drugs is considered in a patient with previously detected breast cancer. An increase in the incidence of pituitary gland, mammary gland, and pancreatic islet cell neoplasia (mammary adenocarcinomas, pituitary and pancreatic adenomas) was observed in the risperidone carcinogenicity studies conducted in mice and rats [see Nonclinical Toxicology (13.1)] . Neither clinical studies nor epidemiologic studies conducted to date have shown an association between chronic administration of this class of drugs and tumorigenesis in humans, but the available evidence is too limited to be conclusive. 

In a long-term maintenance trial of INVEGA TRINZA, elevations of prolactin to above the reference range (>13.13 ng/mL in males and >26.72 ng/mL in females) relative to open-label baseline at any time during the double-blind phase were noted in a higher percentage of males in the INVEGA TRINZA group than in the placebo group (46% vs. 25%) and in a higher percentage of females in the INVEGA TRINZA group than in the placebo group (32% vs. 15%). During the double-blind phase, 1 female (2.4%) in the INVEGA TRINZA group experienced an adverse reaction of amenorrhea, while no potentially prolactin-related adverse reactions were noted among females in the placebo group. There were no potentially prolactin-related adverse reactions among males in either group.

Prior to the double-blind phase (during the 29-week open-label phase of the long-term maintenance trial), the mean (SD) serum prolactin values at baseline in males (N=368) were 17.1 (13.55) ng/mL and 51.6 (40.85) ng/mL in females (N=122). Twelve weeks after a single injection of INVEGA TRINZA at the end of the open-label phase, mean (SD) prolactin values were 25.8 (13.49) ng/mL in males (N=322) and 70.6 (40.23) ng/mL in females (N=107). During the open-label phases 27% of females and 42% of males experienced elevations of prolactin above the reference range relative to baseline, and a higher proportion of females experienced potentially prolactin-related adverse reactions compared to males (7.9% vs. 3.7%). Amenorrhea (4.7%) and galactorrhea (3.1%) were the most commonly observed (≥3%) potentially prolactin-related adverse reactions in females. Among males in the open-label phase, no potentially prolactin-related adverse reaction was observed with a rate greater than 3%.