A 42-year-old woman with bipolar disorder has been on haloperidol 10 mg/day for acute mania for 3 weeks. She now presents with involuntary orofacial grimacing, tongue protrusion, and lip smacking that persist even after dose reduction. Which is the most common extrapyramidal side effect occurring after prolonged antipsychotic exposure?

Explanation

## Extrapyramidal Side Effects: Timeline and Frequency **High-Yield:** Tardive dyskinesia (TD) is the most common late-onset extrapyramidal side effect, occurring in 20–30% of patients on long-term typical antipsychotics and 3–5% on atypical agents after ≥3 months of exposure. ### EPS Classification by Onset and Frequency | EPS Type | Onset | Frequency (Typical APD) | Frequency (Atypical APD) | Mechanism | Reversibility | |---|---|---|---|---|---| | **Acute dystonia** | Hours–days | 5–10% | <1% | D2 blockade → ↑ cholinergic tone | Fully reversible | | **Parkinsonism** | Days–weeks | 15–30% | 3–8% | D2 blockade in substantia nigra | Reversible | | **Akathisia** | Days–weeks | 10–20% | 5–10% | D2 blockade + noradrenergic effects | Reversible | | **Tardive dyskinesia** | Months–years (≥3 mo) | **20–30%** | **3–5%** | D2 supersensitivity, GABA↓ | Often **irreversible** | **Key Point:** The question stem specifies "prolonged antipsychotic exposure" (3 weeks → chronic use) and describes orofacial dyskinesia (involuntary grimacing, tongue protrusion, lip smacking), which is the classic presentation of tardive dyskinesia. ### Tardive Dyskinesia: Clinical Features **Mnemonic:** **BUCCAL** — Buccolingual movements, Uncontrolled orofacial, Choreoathetoid, Choreiform, Akathisia-like restlessness, Limb dyskinesia. 1. **Orofacial dyskinesia** (most common): lip smacking, tongue protrusion, grimacing, jaw clenching 2. **Limb dyskinesia**: choreiform movements of fingers, toes, wrists 3. **Truncal dyskinesia**: rocking, swaying 4. **Respiratory dyskinesia**: irregular breathing (rare, serious) ### Risk Factors for Tardive Dyskinesia - **Older age** (>50 years): 5–10× higher risk - **Female gender**: 1.5–2× higher risk - **Longer duration of antipsychotic use**: cumulative dose effect - **Higher antipsychotic potency**: typical > atypical - **Presence of mood disorder**: bipolar > schizophrenia - **Prior EPS**: suggests D2 sensitivity **Clinical Pearl:** TD may paradoxically worsen initially when the antipsychotic is reduced or discontinued (unmasking phenomenon), but gradual tapering over weeks–months is recommended to minimize this risk. ### Why Other EPS Are Not "Most Common" After Prolonged Exposure **Warning:** Acute dystonia and parkinsonism typically emerge within days to weeks and resolve with dose reduction or anticholinergics. Akathisia also appears early (days–weeks). Only tardive dyskinesia is **specifically a late-onset, prolonged-exposure phenomenon** with cumulative incidence increasing over years [cite:Maudsley Guidelines 2023; Harrison 21e Ch 387].