Management of Partial Response to Valbenazine 80mg for Tardive Dyskinesia
Before adding another medication, first ensure the patient has been on valbenazine 80mg for at least 8 weeks, as improvements continue to increase substantially through 48 weeks of treatment, with elderly patients showing mean AIMS score improvements from -4.5 at week 8 to -8.8 at week 48. 1
First-Line Strategy: Optimize Current Therapy Duration
- Continue valbenazine 80mg for a longer duration rather than immediately adding another agent, as clinical trial data demonstrate progressive improvement over time with sustained treatment 1
- At week 8, only 40% of elderly patients achieved ≥50% AIMS improvement, but this increased to 82.1% by week 48, indicating substantial delayed response 1
- The therapeutic effect of valbenazine has a rapid onset within 2 weeks but continues to improve significantly over months of treatment 2
What NOT to Add
- Do not add anticholinergic medications, as the American Psychiatric Association explicitly advises against their use for tardive dyskinesia—they are indicated only for acute dystonia and parkinsonism, not TD 3
- Avoid adding typical antipsychotics or increasing dopamine receptor blocking agents, as these worsen TD 4
Alternative Pharmacologic Options (Not "Add-On" Therapy)
The evidence does not support combination therapy with multiple VMAT2 inhibitors or adding other agents to valbenazine. Instead, consider these alternatives:
Switch to Deutetrabenazine
- Deutetrabenazine is the other FDA-approved VMAT2 inhibitor for TD with demonstrated efficacy in class 1 studies 3
- Key difference: deutetrabenazine requires twice-daily dosing with food and titration to efficacy/tolerability, versus valbenazine's once-daily dosing 5
- Deutetrabenazine has different drug-drug interaction profile (primarily CYP2D6) and is contraindicated in hepatic impairment 5
Re-evaluate the Causative Agent
- If the patient is still on a dopamine receptor blocking agent, gradually withdraw it if clinically feasible 3, 4
- If antipsychotic therapy must continue, switch to an atypical antipsychotic with lower D2 affinity (e.g., quetiapine, clozapine) 3, 4
- This addresses the root cause rather than simply adding more symptomatic treatment 4
Clinical Pitfalls to Avoid
- Do not prematurely judge treatment failure—the majority of improvement may occur between weeks 8 and 48 1
- Do not combine two VMAT2 inhibitors (valbenazine + deutetrabenazine), as there is no evidence supporting this approach and it increases risk of adverse effects 5
- Ensure psychiatric stability is monitored, as psychiatric symptom scales should remain stable during valbenazine treatment 1
Monitoring During Extended Treatment
- Continue using the Abnormal Involuntary Movement Scale (AIMS) every 3-6 months to objectively track response 3, 4
- Assess both clinician-rated improvement (CGI-TD) and patient-reported outcomes (PGIC), as 85.7% of elderly patients reported being "much improved" or "very much improved" by week 48 1
- Monitor for common adverse events including urinary tract infections (10.9%) and somnolence (10.9%) in elderly patients 1