Risperidone and associated amenorrhea: A report of 5 cases

Background: We report a 5-case series in which risperidone use in usual or lower-than-usual doses was unexpectedly associated with amenorrhea. Case Reports: On regimens of risperidone (1-8 mg/day), 5 psychiatric patients with various diagnoses developed amenorrhea with elevated serum prolactin levels (mean = 121.7 ng/mL; range, 612-229.8 ng/mL). In 4 of 5 cases, menstruation resumed only when risperidone was withdrawn, and in 1 case, menstruation restarted when the dose was tapered. Follow-up serum prolactin levels dropped to a mean of 17.2 ng/mL (range, 6.4-37.6 ng/mL). Conclusion: These findings indicate that the occurrence of amenorrhea during risperidone treatment may be related to elevated serum prolactin levels. This phenomenon may be due either to the dopamine D₂ blocking effect of risperidone or to the large individual variability in the rate at which risperidone is metabolized.