Rates of Hypoprolactinemia in Bipolar Patients Receiving Once-monthly Long-acting Injectable Aripiprazole

Hypoprolactinemia, an often overlooked condition in psychiatric practice, has been suggested to be associated with potential adverse effects on sexual and metabolic functions, similar to those reported in hyperprolactinemia. Recently, numerous studies have indicated that oral aripiprazole can lead to hypoprolactinemia in patients with various psychiatric disorders. However, the frequency and severity of hypoprolactinemia in bipolar patients receiving a 400-mg dose of once-monthly long-acting injectable aripiprazole remain unknown. This study aimed to assess the effects of once-monthly long-acting (400 mg) injectable aripiprazole on prolactin levels in patients with bipolar disorder.

Fifty patients with bipolar disorder (25 women and 25 men) receiving the 400-mg dose of once-monthly long-acting injectable aripiprazole, either as monotherapy or in combination with other psychiatric medications, were recruited for this study.

Overall, the rate of hypoprolactinemia was 52% among the study participants. When stratified by sex, the prevalence was 68% in men and 36% in women. In addition, 28% of male patients and 4% of female patients had serum prolactin levels below 1 ng/mL. Mean serum prolactin levels were significantly higher in women than in men (z=- 3.435, p=0.001). No significant correlation was observed between serum prolactin concentrations and age or treatment duration in either sex.

Once-monthly injectable aripiprazole treatment in bipolar disorder was associated with a relatively high prevalence of hypoprolactinemia in both female and male patients. Given emerging evidence of potential metabolic and sexual effects of hypoprolactinemia, monitoring prolactin levels may be clinically relevant in patients receiving injectable aripiprazole.