How should brexpiprazole (Rexulti) be started, titrated, and monitored in an elderly patient requiring an atypical antipsychotic?

Brexpiprazole (Rexulti) Initiation and Management in Elderly Patients

For elderly patients requiring brexpiprazole, start at 0.5 mg daily for 7 days, increase to 1 mg daily for another 7 days, then advance to the target dose of 2 mg daily on day 15, with a maximum of 3 mg daily if needed after at least 14 additional days at 2 mg. 1

Starting Dose and Titration Schedule

The FDA-approved dosing for elderly patients (specifically for agitation in Alzheimer's dementia, which represents the most vulnerable elderly population) follows a conservative, stepwise approach:

• Days 1-7: 0.5 mg once daily
• Days 8-14: 1 mg once daily
• Day 15 onward: 2 mg once daily (target dose)
• Maximum dose: 3 mg once daily (only after ≥14 days at 2 mg, based on response and tolerability) 1

This slower titration compared to younger adults (who may start at 1 mg) reflects the increased vulnerability of elderly patients to antipsychotic adverse effects 2.

Critical Dose Adjustments Required

Reduce maximum dose to 2 mg daily if:

• Creatinine clearance <60 mL/min 1
• Moderate to severe hepatic impairment (Child-Pugh ≥7) 1

Reduce dose by 50% if:

• Patient is a known CYP2D6 poor metabolizer 1
• Concomitant strong CYP3A4 inhibitors (e.g., clarithromycin, itraconazole) 1
• Concomitant strong CYP2D6 inhibitors (e.g., paroxetine, fluoxetine) 1

Double the dose if:

• Concomitant strong CYP3A4 inducers (e.g., rifampin, carbamazepine) are used, then taper back down over 1-2 weeks when inducer is stopped 1

Monitoring Requirements

Before Initiating Treatment

The 2016 APA guidelines mandate a comprehensive risk-benefit discussion with the patient (if feasible) and surrogate decision-maker before starting any antipsychotic in elderly patients with dementia 3. This discussion must explicitly address:

• Black box warning: Increased mortality risk in elderly patients with dementia-related psychosis 1
• That brexpiprazole should only be used when symptoms are severe, dangerous, or cause significant distress 3
• That non-pharmacological interventions should be attempted first 3

Ongoing Safety Monitoring

Monitor at each visit for:

• Extrapyramidal symptoms: Akathisia occurs in approximately 5.5% (though only marginally higher than placebo at 4.6%) 4
• Sedation/somnolence: Reported in 3.7% vs 1.8% placebo 5
• Cerebrovascular events: 0.5% incidence in pooled trials 5
• Falls risk: Given the elderly population's vulnerability 2
• Weight gain: Approximately 10% of patients gain ≥7% body weight (vs 4% placebo), though effects are modest short-term 4

Metabolic monitoring:

• Minimal effects on glucose and lipids observed in trials 4
• Minimal prolactin elevation 4
• No clinically significant QTc prolongation 4

Cognitive assessment:

• No worsening of cognition observed in 24-week trials 5
• Use a quantitative measure to assess treatment response 3

Treatment Response Assessment

At 4 weeks: If no clinically significant response after 4 weeks at an adequate dose, taper and discontinue the medication 3. This is critical—do not continue ineffective treatment in this vulnerable population.

If effective: Periodically reassess the continued need for treatment through discussion with patient/surrogate, reviewing initial goals, observed benefits, side effects, and risks of continued exposure 3.

Key Safety Considerations

The 2025 JAGS geriatric emergency guidelines found that oral antipsychotics (particularly quetiapine) had the best safety profile, with serious adverse events occurring in 16.8% of elderly patients receiving antipsychotics or anxiolytics 2. Favor oral administration over IV/IM routes, which increase adverse event risk 2.

Common adverse events in elderly patients on brexpiprazole include headache (7.6-8%), fatigue (15.2%), and restlessness (12.9%), with most being mild to moderate 6, 5. Discontinuation due to adverse events occurs in approximately 6-8% of patients 6, 5.

Critical Pitfall to Avoid

Brexpiprazole is NOT a PRN medication 1, 7. It is a maintenance treatment requiring daily administration with gradual titration. Using it "as needed" for breakthrough agitation is inappropriate and ineffective.

The medication requires 2-3 weeks to reach therapeutic dosing in elderly patients, so plan accordingly and maintain non-pharmacological interventions during titration 1.