PHARM | 1st Gen Antipsychotics Haloperidol

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