💊 PHARM STUDY GUIDE: HALOPERIDOL (Haldol) Class: First-generation antipsychotic

🧠 MOA (80/20): High-potency D2 receptor antagonist → ↓ mesolimbic dopamine (helps positive symptoms). D2 block in other tracts drives side effects.

🧭 Dopamine Pathways (clinical relevance):

• Mesolimbic: D2 block → ↓ hallucinations/delusions ✅.
• Nigrostriatal: D2 block → EPS/pseudoparkinsonism ⚠️.
• Tuberoinfundibular: D2 block → ↑ prolactin (galactorrhea, menstrual changes).

📋 Indications (common): Schizophrenia; acute agitation (IM lactate); Tourette’s tics; long-term adherence with decanoate IM depot (not IV). Some off-label (e.g., delirium) are used with caution.

⚠️ Boxed/Geriatric Warning: Not approved for dementia-related psychosis; ↑ mortality and stroke risk—avoid unless benefits outweigh risks.

❤️ Cardiac Risks: QT prolongation/TdP; risk higher with IV use and high doses; correct K/Mg, monitor ECG, avoid other QT-prolongers. (IV haloperidol is not FDA-approved.)

🔥 Life-Threatening:

• NMS: fever, rigidity, AMS, autonomic instability → stop drug, ICU care.
• Severe hematologic/hepatic events (rare) → check CBC/LFTs if symptomatic.

🩺 Common/Important AEs: EPS (akathisia, dystonia, parkinsonism), TD with chronic use; sedation/orthostasis less than many SGAs due to weaker H1/α1 effects. Use AIMS to screen for TD. Treat acute dystonia/akathisia with anticholinergic or dose change.

💊 Formulations & PK pearls:

• IM lactate: rapid control (peaks ~20–40 min).
• PO: peaks 2–6 h; bioavailability ~60%.
• IM decanoate: depot; peak ≈6 days; t½ ≈3 weeks; IM only.
• Metabolism: hepatic CYP2D6/CYP3A4 → active hydroxyhaloperidol. Poor 2D6 metabolizers: ↑ EPS risk.

🚫 Major Contra/Interactions (high-yield):

• Avoid with strong QT-prolongers (e.g., pimozide, quinidine; many azoles) → TdP.
• CYP inhibitors ↑ levels/QT (e.g., ketoconazole + paroxetine combo raised QTc). Ritonavir/fluvoxamine/fluoxetine can elevate levels—consider dose ↓ and ECG.
• CYP inducers (rifampin, carbamazepine) ↓ levels → relapse risk.
• Parkinson’s disease: avoid—worsens motor symptoms.

🧑‍⚕️ Nursing/Monitoring:

• Baseline and periodic ECG, vitals; correct electrolytes.
• EPS/TD checks (AIMS), fall precautions.
• Prolactin-related effects counseling.
• Reassess need regularly in older adults; document non-pharm attempts for BPSD.

🎯 Top 5 NCLEX Takeaways:

1. High-potency D2 blocker → great for positive sx, high EPS/TD risk.
2. QT/TdP risk (esp. IV/high dose) → ECG & avoid QT drugs.
3. Not for dementia psychosis (boxed warning).
4. Decanoate = IM only depot; no IV.
5. Watch for NMS—fever + rigidity = emergency