Population Pharmacokinetic Analysis and Model-Based Simulations of Aripiprazole for a 1-Day Initiation Regimen for the Long-Acting Antipsychotic Aripiprazole Lauroxil.

Unlabelled: BACKGROUND AND OBJECTIVES: Aripiprazole lauroxil (AL), a long-acting injectable antipsychotic for the treatment of schizophrenia, requires 21 days of oral aripiprazole supplementation upon initiation (21-day initiation regimen). An alternative 1-day initiation regimen utilizing a nano-crystalline milled dispersion of AL (AL) plus a single 30 mg oral aripiprazole dose achieved aripiprazole concentrations associated with therapeutic doses of aripiprazole in the same time frame as the 21-day initiation regimen when starting AL (441 or 882 mg). A population pharmacokinetic (PopPK) model was developed to describe aripiprazole pharmacokinetics following administration of AL, AL and oral aripiprazole, and evaluate dosing scenarios likely to be encountered in clinical practice.

Methods: In total, 12,768 plasma aripiprazole concentrations from 343 patients (from 4 clinical studies) were included in the PopPK analysis and used to construct the model.

Results: Concomitant administration of the 1-day initiation regimen with all approved AL dosing regimens (441, 662, or 882 mg monthly, 882 mg every 6 weeks, or 1064 mg every 2 months) is predicted to achieve aripiprazole concentrations associated with therapeutic doses of AL using the 21-day initiation regimen within 4 days, maintaining these concentrations until the next AL dose. Administration of the first AL injection 10 days after the 1-day initiation regimen resulted in median aripiprazole concentrations just before the second dose of AL ≥ 77% of that when coadministered on the same day. Coadministration of AL with a single AL injection was predicted to be effective in rapidly re-establishing concentrations associated with therapeutic doses of AL following dose delay.

Conclusions: Model-based simulations demonstrate that the 1-day initiation regimen is suitable for starting treatment with all AL doses, allowing a window of ≤ 10 days between initiation and AL administration. AL may also be used to re-establish concentrations associated with therapeutic doses of AL in conjunction with a delayed AL dose.