Droperidol (Inapsine)

What it treats

Droperidol is FDA-approved for the reduction of nausea and vomiting associated with surgical and diagnostic procedures. In practice it's also widely used off-label in emergency departments for acute agitation, severe headache, and hyperemesis, backed by decades of experience. It works quickly, which is what makes it valuable in acute settings.

Droperidol isn't used for chronic maintenance treatment of schizophrenia or any other outpatient psychiatric condition. Its role is a single dose or a short course in a monitored setting.

How it works

Droperidol is a butyrophenone antipsychotic, the same chemical family as haloperidol. It blocks dopamine D2 receptors, which calms acute agitation and reduces nausea signals in the brain. Its onset by intramuscular or intravenous route is fast, often within minutes, and its effect lasts a few hours.

Receptor mechanism (detail)

Droperidol is a D2 receptor antagonist with additional alpha-1 blockade that can cause some blood pressure lowering. Its effect on cardiac hERG potassium channels drives the QTc prolongation flagged in the boxed warning.

Potency and typical dosing pattern

Ranges are typical framework only, not a prescription for any individual.

For acute agitation or postoperative nausea, a typical dose is 2.5 to 5 mg intramuscularly or intravenously as a single dose. It can be repeated per protocol if needed. The prescriber or emergency clinician sets the dose based on the situation.

Safety monitoring

• Continuous ECG monitoring for two to three hours after a dose to watch for QTc changes. This is the standard framework.
• Baseline potassium and magnesium in the acute setting when possible, low levels raise QTc risk.
• Blood pressure and heart rate monitored around and after the dose.
• Sedation level checked as the effect wears off.
• Not typically used in patients with known long QT syndrome or with other QTc-prolonging drugs on board.

Metformin co-commencement: Aoife Carolan / Schizophrenia Bulletin guideline.

A clinical guideline led by Aoife Carolan strongly recommends co-commencing metformin alongside high-risk antipsychotics like olanzapine or clozapine. This proactive approach helps mitigate severe metabolic side effects, significantly reducing antipsychotic-induced weight gain and improving insulin resistance. The Schizophrenia Bulletin guideline states that when prescribing olanzapine or clozapine, metformin should be initiated immediately to prevent weight gain and cardiometabolic issues. Droperidol is used only for single-dose or short-course acute care, not chronic treatment, so the co-commencement framework doesn't apply here.

Typical titration used in the guideline: 500 mg once daily, then 500 mg twice daily after one week, then 500 mg increments every two weeks as tolerated, up to 1000 mg twice daily by about week six. Contraindicated with eGFR below 30 mL/min/1.73 m². Renal function is checked annually and metformin is held during acute illness or dehydration.

Source: Carolan A, et al. Metformin for the Prevention of Antipsychotic-Induced Weight Gain: Guideline Development and Consensus Validation. Schizophrenia Bulletin. 2025;51(5):1193 to 1203.

What to expect

Common side effects

• Sedation.
• Mild drop in blood pressure.
• Restlessness or akathisia after the dose wears off.
• Nausea (less common, occasionally paradoxical).
• Dysphoria in some people.

Serious side effects and warnings

Boxed warning. Droperidol carries an FDA boxed warning for QTc prolongation and torsades de pointes, including at doses at or below the recommended range. Continuous ECG monitoring around the dose is the recommended framework.

• QTc prolongation and torsades de pointes. The central serious risk. Care teams screen for known long QT syndrome, other QT-prolonging drugs, and electrolyte imbalance before use.
• Extrapyramidal reactions. Acute dystonia and akathisia can occur, treatable with diphenhydramine or benztropine.
• Neuroleptic malignant syndrome. Rare but serious.
• Hypotension. Can occur, especially in volume-depleted patients.

This isn't medical advice. Any concern about a serious side effect should be raised with the treating clinician promptly.

Sexual side effects

Not typically a concern with single-dose or short-course use.

Weight, appetite, and sleep

Not typically a concern with single-dose or short-course use. Sedation for a few hours after a dose is common.

Starting and dosing basics

This section is general background, not a dosing instruction. Droperidol is given by IM or IV injection in acute care settings. It isn't a take-home medication. The dose and route depend on the clinical situation and the protocols of the department using it.

Missed doses and interactions

Because droperidol is a single-dose acute care medication, missed doses aren't a routine concern. Interactions matter in the acute setting: other QTc-prolonging drugs (some antibiotics, some antipsychotics, some antiarrhythmics) increase risk. The care team screens for those before dosing.

Stopping and tapering

Not applicable in the acute care context. Droperidol isn't used long-term.

Pregnancy and breastfeeding

Droperidol is sometimes used for hyperemesis in pregnancy under specialist care. Because it's a single-dose or short-course medication in monitored settings, decisions are made case by case with the treating team. This isn't medical advice.

Cost and generic availability

Droperidol is generic and inexpensive per dose. Its availability in the U.S. has been variable over the years, dropping after the boxed warning was added in 2001 and rebounding as clinicians pushed back on the strength of the warning. Availability varies by hospital and pharmacy.

Common questions

Why is droperidol used in the ER but not in outpatient psychiatry? Its fast onset, short duration, and reliable effect on acute agitation and nausea make it valuable in acute settings where a person can be continuously monitored. Its QTc profile and short half-life mean it isn't suited to chronic treatment. Outpatient antipsychotics need to work over the long term with tolerable ongoing side effects, which isn't droperidol's role.

What's the story on the boxed warning? In 2001 the FDA added a boxed warning based on post-marketing reports of QTc prolongation and sudden cardiac death. Many emergency medicine clinicians have argued that the underlying data was weaker than the warning implied, and multiple studies since have shown droperidol is safe at typical ED doses when standard precautions are followed. The warning remains on the label.

Is it stronger than haloperidol for agitation? Onset is faster, and some clinicians find it calms agitation more reliably at typical ED doses. Direct head-to-head evidence is limited.

Is it addictive? No. Droperidol has no abuse potential.

Questions to ask the treating clinician

• Why are we using droperidol here?
• How long will monitoring continue after the dose?
• Are there other options if I've had a bad reaction to droperidol before?
• What should I watch for after I leave the ER or recovery area?

Sources

This guide draws on current prescribing information and public health references. It is reviewed for clinical accuracy and updated as guidance changes, and current as of June 8, 2026.

• U.S. Food and Drug Administration. Droperidol prescribing information.
• MedlinePlus, U.S. National Library of Medicine. Droperidol.
• American College of Emergency Physicians clinical policy on acute agitation.
• Perkins J, Ho JD, Vilke GM, DeMers G. American Academy of Emergency Medicine position statement on safety of droperidol use in the emergency department. J Emerg Med. 2015.
• Carolan A, et al. Metformin for the Prevention of Antipsychotic-Induced Weight Gain: Guideline Development and Consensus Validation. Schizophrenia Bulletin. 2025;51(5):1193 to 1203.