VMAT2 inhibitors are the first effective pharmacologic treatment for tardive dyskinesia, and their arrival has substantially changed how this previously near-untreatable condition is managed. The mechanism is unusual: rather than acting on receptors, VMAT2 inhibitors block the vesicular monoamine transporter that packages dopamine (and other monoamines) into presynaptic storage vesicles. With packaging blocked, presynaptic dopamine is degraded by MAO before release. Less dopamine available for release. Less dopaminergic signaling overall.
- Class
- Vesicular monoamine transporter 2 (VMAT2) inhibitors
- Mechanism
- Inhibit VMAT2 → prevent packaging of monoamines (DA, NE, 5-HT) into presynaptic vesicles → reduced presynaptic monoamine availability → reduced dopaminergic signaling in nigrostriatum (treats hyperkinetic movements)
- Typical dose
- Valbenazine 40-80 mg daily; deutetrabenazine 12-48 mg/day in divided doses
- Half-life
- Valbenazine ~15-22h; deutetrabenazine ~9-10h (deuterated for longer half-life vs tetrabenazine)
- FDA indications
- Tardive dyskinesia (valbenazine, deutetrabenazine); Huntington's disease chorea (valbenazine, deutetrabenazine, tetrabenazine)
- Key adverse effects
- Somnolence, fatigue, akathisia, parkinsonism, depression (tetrabenazine has black box for suicidality; valbenazine/deutetrabenazine have better profile), QTc prolongation
- Representative agents
- Valbenazine (Ingrezza), deutetrabenazine (Austedo), tetrabenazine (Xenazine — older agent, more side effects)
Black box: Tetrabenazine: depression and suicidality. Newer agents have improved profile.
Game-changing for tardive dyskinesia — previously few effective options. Valbenazine and deutetrabenazine are newer agents (FDA approved 2017) with much better tolerability than older tetrabenazine. High cost is the constraint.
For tardive dyskinesia — the chorea-athetoid movements produced by chronic D2 blockade with compensatory dopamine receptor supersensitivity — reducing presynaptic dopamine availability attenuates the hyperkinetic movements. The effect is often substantial, and importantly, the underlying antipsychotic doesn't have to be discontinued for VMAT2 inhibitors to work.
VMAT2 inhibitors treat tardive dyskinesia and other hyperkinetic disorders by reducing dopamine packaging into synaptic vesicles — depleting the dopamine available for release.
Mechanism note: VMAT2 inhibitors treat tardive dyskinesia presynaptically — depleting releasable dopamine — which lets the causative antipsychotic often continue; monitor for sedation, parkinsonism, and depression.
Three agents: valbenazine (Ingrezza, FDA 2017), deutetrabenazine (Austedo, FDA 2017), and tetrabenazine (Xenazine, older). Valbenazine and deutetrabenazine are the newer agents with substantially better tolerability profiles than tetrabenazine. Both are FDA-approved for TD; deutetrabenazine and tetrabenazine are also approved for Huntington's chorea.
Tetrabenazine — the older agent — carries a black-box warning for depression and suicidality, and its side effect profile (sedation, parkinsonism, depression) limited its use. The newer agents preserve the antidyskinetic effect with substantially better tolerability.
Side effects of valbenazine and deutetrabenazine: somnolence, fatigue, modest akathisia, parkinsonism, occasional depression, QTc prolongation. Generally well-tolerated.
Cost is the constraint. Both newer agents are brand-only and expensive — prior authorization is typical. For the patient with TD that significantly affects quality of life, the benefit usually justifies the access work. For mild TD without functional impact, the cost-benefit calculation is less clear.
Prevention remains the priority — minimize antipsychotic exposure when possible, prefer agents with lower TD risk (clozapine, quetiapine), annual AIMS exams. When TD develops, VMAT2 inhibitors are what we have, and they work.