Valbenazine for Tardive Dyskinesia

Clozapine and tardive dyskinesia in patients with schizophrenia: A systematic review

BACKGROUND

It is commonly recommended that a switch to clozapine be implemented in the face of tardive dyskinesia, even if current treatment involves another "atypical" agent. However, reports do indicate clozapine carries a liability for tardive dyskinesia.

AIMS

This review sought to evaluate clozapine in relation to tardive dyskinesia in the context of available evidence.

METHODS

Medline, Embase, and PsycINFO databases were searched for studies published in English, using the keywords: clozapine AND tardive dyskinesia OR TD. References from major review articles were searched for additional relevant publications. Studies were included if they investigated: tardive dyskinesia in clozapine-treated patients diagnosed with schizophrenia spectrum disorders, and reported on two or more assessments of tardive dyskinesia severity measured by the Abnormal Involuntary Movement Scale; or clozapine's tardive dyskinesia liability.

RESULTS

In total, 513 unique citations were identified and 29 reports met the inclusion criteria. Thirteen studies suggest clozapine reduces dyskinetic symptoms over time (n=905 clozapine-treated participants); however, the minimum required dose and effect of withdrawal requires further investigation. The majority of reports which address clozapine's liability for tardive dyskinesia are case studies (11 of 14 reports, 79%), and clozapine was only the first-line treatment in one of the remaining three studies reporting treatment-emergent dyskinetic symptoms with clozapine in 12% of patients. No significant between-drug differences were identified comparing clozapine's risk to other atypical antipsychotics.

CONCLUSIONS

Research to date supports switching to clozapine for the purpose of reducing tardive dyskinesia risk and/or treating existing tardive dyskinesia, but prospective randomized controlled trials are necessary if we are to substantiate existing recommendations.

Comparing pharmacologic mechanism of action for the vesicular monoamine transporter 2 (VMAT2) inhibitors valbenazine and deutetrabenazine in treating tardive dyskinesia: does one have advantages over the other?

The two approved treatments for tardive dyskinesia both inhibit the vesicular monoamine transporter type 2 (VMAT2) yet have pharmacologic properties that distinguish one from the other. Knowing these differences may help optimize which treatment to select for individual patients.

Treatment of tardive dyskinesia with VMAT-2 inhibitors: a systematic review and meta-analysis of randomized controlled trials

Aim

The aim of this study was to summarize the characteristics, efficacy, and safety of vesicular monoamine transporter-2 (VMAT-2) inhibitors for treating tardive dyskinesia (TD).

Materials and methods

We conducted a literature search in PubMed, Cochrane Database, and ClinicalTrials.gov, screening for systematic reviews, meta-analyses or double-blind, randomized, placebo-controlled trials (DBRPCTs) reporting efficacy or safety data of VMAT-2 inhibitors (tetrabenazine, deutetrabenazine, and valbenazine) in patients with TD. A random effects meta-analysis of efficacy and safety data from DBRPCTs was performed.

Results

Two acute, 12-week DBRPCTs with deutetrabenazine 12–48 mg/day (n=413) and 4 acute, 4–6-week double-blind trials with valbenazine 12.5–100 mg/day (n=488) were meta-analyzable, without meta-analyzable, high-quality data for tetrabenazine. Regarding reduction in total Abnormal Involuntary Movement Scale (AIMS) scores (primary outcome), both deutetrabenazine (k=2, n=413, standardized mean difference [SMD] =−0.40, 95% confidence interval [CI] =−0.19, −0.62, p<0.001; weighted mean difference (WMD) =−1.44, 95% CI =−0.67, −2.19, p<0.001) and valbenazine (k=4, n=421, SMD =−0.58, 95% CI =−0.26, −0.91, p<0.001; WMD =−2.07, 95% CI =−1.08, −3.05, p<0.001) significantly outperformed placebo. Results were confirmed regarding responder rates (≥50% AIMS total score reduction; deutetrabenazine: risk ratio [RR] =2.13, 95% CI =1.10, 4.12, p=0.024, number-needed-to-treat [NNT] =7, 95% CI =3, 333, p=0.046; valbenazine: RR =3.05, 95% CI =1.81, 5.11, p<0.001, NNT =4, 95% CI =3, 6, p<0.001). Less consistent results emerged from patient-rated global impression-based response (p=0.15) and clinical global impression for deutetrabenazine (p=0.088), and for clinical global impression change for valbenazine (p=0.67). In an open-label extension (OLE) study of deutetrabenazine (≤54 weeks) and a dose-blinded valbenazine study (≤48 weeks), responder rates increased over time. With valbenazine, discontinuation effects were studied, showing TD symptom recurrence towards baseline severity levels within 4 weeks after valbenazine withdrawal. No increased cumulative or specific adverse (AEs) events versus placebo (acute trials) in extension versus acute trial data were observed.

Conclusion

The 2 VMAT-2 inhibitors, valbenazine and deutetrabenazine, are effective in treating TD, both acutely and long-term, without concerns about increased risk of depression or suicide in the TD population. No head-to-head comparison among VMAT-2 inhibitors and no high-quality, meta-analyzable data are available for tetrabenazine in patients with TD.