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VMAT2 inhibitors are drugs that block the vesicular monoamine transporter 2 (VMAT2)—a protein responsible for packaging monoamine neurotransmitters (like dopamine, serotonin, norepinephrine, and histamine) into synaptic vesicles for release into the synaptic cleft.
🧪 What is VMAT2?
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VMAT2 (Vesicular Monoamine Transporter 2) is found in neurons and is critical for:
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Storing monoamines (especially dopamine) in vesicles
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Protecting them from degradation by enzymes like monoamine oxidase (MAO)
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💊 What Do VMAT2 Inhibitors Do?
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Block VMAT2, which leads to:
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Decreased dopamine release
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Depletion of monoamines in presynaptic terminals
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This makes them useful for conditions where dopamine hyperactivity causes symptoms.
📋 Examples of VMAT2 Inhibitors
| Drug | Indication |
|---|---|
| Tetrabenazine | Chorea in Huntington's disease |
| Deutetrabenazine | Chorea, tardive dyskinesia (FDA-approved) |
| Valbenazine | Tardive dyskinesia (selective VMAT2 inhibitor) |
🧠 Clinical Uses
✅ 1. Tardive Dyskinesia (TD)
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Involuntary, repetitive movements caused by long-term dopamine receptor-blocking drugs (e.g., antipsychotics)
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Valbenazine and deutetrabenazine are first-line agents
✅ 2. Huntington’s Disease (Chorea)
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Reduces excessive movement caused by dopamine dysregulation
⚠️ Side Effects
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Depression and suicidality (especially with tetrabenazine)
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Parkinsonism (due to dopamine depletion)
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Fatigue, somnolence
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QT prolongation (dose-dependent)
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Risk of neuroleptic malignant syndrome (rare)
🔬 Mechanism Summary
Normal: VMAT2 → packages dopamine → synaptic vesicles → dopamine release
With VMAT2 inhibitor: ↓ dopamine storage → ↓ dopamine release → ↓ dyskinesia
🔎 Related Concepts
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Reserpine: An older, irreversible VMAT inhibitor, rarely used due to severe side effects (depression, hypotension).
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Selective VMAT2 inhibitors: Better tolerated, newer agents for movement disorders.
🧠 Memory Tip
"VMAT2 inhibitors help mute dopamine where it’s too loud—like in tardive dyskinesia or Huntington's chorea."
Would you like a comparison chart of VMAT2 inhibitors or a clinical vignette question for practice?
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