Available LAI Aripiprazole Formulations for Bipolar Maintenance
Two long-acting injectable formulations of aripiprazole monohydrate are FDA-approved for bipolar I disorder maintenance: aripiprazole once-monthly 400 mg (AOM 400) and aripiprazole 2-month ready-to-use 960 mg (Ari 2MRTU 960). 1, 2
Formulation Details
Once-Monthly Formulation (AOM 400)
- Dosing: 400 mg administered intramuscularly every 4 weeks
- FDA approval: Approved for bipolar I disorder maintenance since 2017 3
- Delivery: Requires reconstitution before administration
Two-Month Ready-to-Use Formulation (Ari 2MRTU 960)
- Dosing: 960 mg administered intramuscularly every 8 weeks (also available as 720 mg dose)
- FDA approval: More recently approved for both schizophrenia and bipolar I disorder maintenance 4, 2
- Delivery: Ready-to-use formulation requiring no reconstitution 4
Clinical Efficacy Evidence
The once-monthly formulation demonstrated robust efficacy in the pivotal maintenance trial, with 73.5% of patients remaining free from mood episode recurrence at 52 weeks versus 48.9% with placebo (NNT = 5) 5. This translates to preventing one relapse for every 5 patients treated.
The efficacy breakdown by episode type shows:
- Manic episodes: NNT = 5 (highly effective)
- Mixed episodes: NNT = 4 (highly effective)
- Depressive episodes: No significant benefit demonstrated 5
A critical caveat: Both LAI formulations are proven effective for preventing manic and mixed episodes but their efficacy for preventing bipolar depression remains unproven 1. This is an important limitation when counseling patients.
Pharmacokinetic Considerations
The 2-month formulation delivers mean steady-state aripiprazole concentrations of 263 ng/mL, well above the therapeutic threshold of ≥95 ng/mL associated with 4.41-fold lower relapse risk 6. The once-monthly formulation provides comparable exposure with more frequent dosing 4.
Both formulations maintain therapeutic aripiprazole levels throughout their respective dosing intervals, with the 2-month formulation offering the practical advantage of less frequent administration while maintaining efficacy comparable to the monthly option 2.
Safety Profile
Discontinuation due to adverse events was actually lower with AOM 400 (17.4%) versus placebo (25.6%) 5, indicating good tolerability. The most common adverse events are:
- Akathisia (most frequent, occurring in ≥10% of patients combined with restlessness at 23%) 7
- Injection site pain
- Sedation
- Weight increase 1
Most adverse events are mild to moderate in severity 7.
Clinical Bottom Line
Aripiprazole is the only dopamine partial agonist available in LAI formulations for bipolar I disorder maintenance 1, 8. The choice between monthly and 2-month formulations should be based on patient preference for injection frequency, as both maintain therapeutic drug levels and demonstrate comparable efficacy profiles 2.