Haloperidol — Haldol — is the high-potency FGA workhorse. It is the most studied, most familiar, and most accessible antipsychotic in emergency settings. In every emergency department in the world that handles psychiatric agitation, haloperidol is part of the toolkit. Its pharmacology is essentially pure D2 antagonism with minimal off-target effects.
- Class
- High-potency first-generation antipsychotic
- Mechanism
- Potent D2 antagonist; minimal H1, M1, or alpha-1 effects
- Typical dose
- PO 0.5-20 mg/day; IM 2-10 mg per dose for acute agitation; decanoate 50-200 mg IM monthly
- Half-life
- ~24 hours (PO, range ~15-37h); IM ~21 hours; decanoate ~3 weeks
- FDA indications
- Schizophrenia, acute psychosis, severe agitation, Tourette syndrome, delirium agitation (off-label)
- Key adverse effects
- Acute dystonia (high incidence), akathisia, parkinsonism, tardive dyskinesia, NMS, QTc prolongation (particularly with IV)
Black box: Increased mortality in elderly patients with dementia-related psychosis
Rapid IM agitation control: workhorse for ED and inpatient acute psychiatric agitation. IV haloperidol associated with QTc prolongation and torsades — use cautiously, ECG monitoring. Often combined with lorazepam ("B-52": haldol 5 + benadryl 50 + ativan 2 — historical regimen).
For acute agitation, intramuscular haloperidol 2-10 milligrams produces antipsychotic effect within about thirty minutes. It is often combined with intramuscular lorazepam for synergistic effect and with benztropine prophylactically to prevent acute dystonia. The classic combination — sometimes called "B-52" historically — was haloperidol 5 mg plus diphenhydramine 50 mg plus lorazepam 2 mg. Modern regimens vary but the principle persists: D2 blockade for the psychosis, GABA enhancement for the calming, anticholinergic for the EPS prevention.
Haloperidol is the prototype high-potency FGA — tight, selective D2 blockade that delivers strong antipsychotic effect and strong EPS in the same stroke.
Mechanism note: Haloperidol's value is potent, hemodynamically clean antipsychotic effect; its cost is high EPS burden. The decanoate form solves adherence in chronic psychosis.
The EPS profile is haloperidol's defining clinical concern. Acute dystonia is especially common in young men in the first hours to days. Akathisia is frequently underrecognized and undertreated. Parkinsonism develops over days to weeks. Tardive dyskinesia is the long-term risk that accumulates over months and years. Prophylactic anticholinergic — benztropine 1-2 mg — is often added with each haloperidol dose for patients at high risk, particularly young men receiving IM doses.
IV haloperidol can prolong QTc and has been associated with torsades. ECG monitoring is appropriate when IV use is prolonged or combined with other QTc-prolonging agents.
Haloperidol decanoate is the long-acting injectable form, dosed monthly in oily depot. It was foundational for adherence-limited schizophrenia, predating modern SGA LAIs. It is largely supplanted by paliperidone palmitate, aripiprazole maintena, and other SGA LAIs where available — those have better tolerability profiles. Haloperidol decanoate remains in use in cost-constrained settings and for patients with established response.
For rapid agitation control, haloperidol remains a first-line tool. For long-term schizophrenia maintenance, SGA LAIs have largely taken over. The choice today reflects the setting and the patient's specific situation.
- Cost
- Generic: ~$10-30/month oral. Decanoate (LAI) ~$30-80/dose.
- Generic status
- Generic for decades.
- Formulary typical
- Tier 1 generic. No PA.
- Access friction
- Pharmacies universally stock oral. Decanoate sometimes requires advance order. IM in ED is universally available.
Prescriber tip: For rapid agitation, IM haloperidol + IM lorazepam + IM benztropine is the standard combination — cheap, reliable, every ED has it. Reserve for acute use; chronic use rare today.