Exposure-Response Analysis for Aripiprazole Once-Monthly in Patients Diagnosed With Bipolar I Disorder

Aripiprazole once-monthly (AOM) is approved for the maintenance monotherapy treatment of bipolar I disorder (BP-I) in adults. A previously developed population pharmacokinetic model was validated by applying it to data from patients diagnosed with BP-I. The model was then used to generate aripiprazole exposures for an exposure-response model intended to describe the relationship between aripiprazole exposure and time to recurrence of any mood episode in patients with BP-I. The BP-I data were best described by a continuous model in which higher aripiprazole exposure was associated with a lower risk of recurrence. For each 1 ng/mL increase in aripiprazole plasma concentration, the predicted hazard for recurrence decreased by 0.34%. An aripiprazole plasma concentration of 95 ng/mL (clinically relevant in schizophrenia) was tested in a separate categorical model and was a significant predictor of time to recurrence (P = .0270), with a 36% (1.55-fold) decrease in the predicted risk of recurrence with an aripiprazole concentration of ≥95 versus <95 ng/mL. Plasma aripiprazole concentration was identified as an important predictor of recurrence in patients diagnosed with BP-I treated with AOM, highlighting the importance of maintenance therapy. A 95 ng/mL threshold is relevant in BP-I, but with a smaller effect size compared with that in schizophrenia.