A 28-year-old man with schizophrenia has been on antipsychotic therapy for 6 months. He develops involuntary repetitive movements of the mouth, tongue, and jaw. Which is the most common antipsychotic-induced movement disorder in patients on long-term therapy?

Explanation

## Most Common Antipsychotic-Induced Movement Disorder **Key Point:** Tardive dyskinesia (TD) is the most common late-onset extrapyramidal side effect, occurring in 20–30% of patients on chronic antipsychotic therapy, particularly with typical (first-generation) antipsychotics. ### Clinical Features of Tardive Dyskinesia - **Onset:** Typically after 6–12 months of continuous antipsychotic use (or higher cumulative dose). - **Movements:** Involuntary, repetitive orofacial dyskinesias (lip smacking, tongue protrusion, jaw movements), limb dyskinesias, and truncal movements. - **Irreversibility:** Often persists even after drug discontinuation, making it the most concerning extrapyramidal side effect. - **Risk factors:** Older age, female gender, mood disorders, higher antipsychotic dose, and longer duration of therapy. ### Comparison of Antipsychotic-Induced Movement Disorders | Movement Disorder | Onset | Mechanism | Reversibility | Frequency | | --- | --- | --- | --- | --- | | **Tardive Dyskinesia** | Months–years | Dopamine supersensitivity | Often irreversible | 20–30% (chronic use) | | **Acute Dystonia** | Minutes–hours | Acute dopamine blockade + cholinergic imbalance | Reversible (anticholinergic) | 5–10% (early) | | **Akathisia** | Days–weeks | Dopamine blockade in limbic/mesocortical regions | Partially reversible | 20–25% | | **Parkinsonism** | Days–weeks | Dopamine blockade in nigrostriatal pathway | Reversible (anticholinergic/beta-blocker) | 15–20% | **High-Yield:** TD is dose- and duration-dependent, more common with typical antipsychotics (haloperidol, chlorpromazine) than atypicals, and has NO reliable pharmacological treatment once established. **Clinical Pearl:** The risk of TD is one reason atypical antipsychotics (risperidone, olanzapine, quetiapine) are preferred as first-line agents in modern practice, though they are not risk-free. **Mnemonic — Early vs. Late Extrapyramidal Side Effects:** - **EARLY (days–weeks):** Acute Dystonia, Akathisia, Parkinsonism (DAP) — all reversible. - **LATE (months–years):** Tardive Dyskinesia (TD) — often irreversible.