Haloperidol (Haldol)

What it treats

Haloperidol is approved by the U.S. Food and Drug Administration to treat schizophrenia, Tourette syndrome, and severe behavioral problems that have not responded to other treatments. In hospital and emergency settings, it is also widely used to calm acute agitation, given by mouth, by intramuscular injection, or occasionally intravenously. That emergency use is not always specifically on the label, but it is well established and reflects decades of experience.

Haloperidol is one of the oldest antipsychotics still in regular use. It is not usually a first choice for maintenance treatment of schizophrenia today, because newer antipsychotics generally have fewer movement side effects, but it remains an important option, especially when cost, availability, or a long-acting injection is a factor.

How it works

Haloperidol is a first-generation antipsychotic, sometimes called a typical antipsychotic. Nerve cells in the brain pass messages using chemical messengers, and dopamine is one of them. In psychosis and mania, dopamine activity in certain circuits is thought to be too high. Haloperidol works by strongly blocking dopamine at a specific receptor called D2, which quiets that overactive signaling and reduces symptoms like hallucinations, delusions, and severe agitation.

That strong, targeted block on dopamine is what makes haloperidol effective. It is also what gives it a higher rate of movement side effects than the newer antipsychotics. How that translates into day-to-day experience is not always predictable, and it is worth being honest about that.

Receptor mechanism (detail)

Haloperidol is a high-affinity D2 receptor antagonist with minimal action at muscarinic, histaminergic, or α-adrenergic receptors. That relatively "clean" profile means it does not cause much sedation, dry mouth, orthostasis, or weight gain the way older sedating antipsychotics like chlorpromazine do. The trade-off is that strong, selective D2 blockade produces the highest rate of extrapyramidal side effects (EPS), parkinsonism, akathisia, and acute dystonic reactions, and the highest long-term risk of tardive dyskinesia in the antipsychotic class. It also raises prolactin.

Potency and typical dosing pattern

Ranges are typical framework only, not a prescription for any individual. Haloperidol is very high-potency by milligram, small doses do meaningful work, and doses are much lower than for older low-potency antipsychotics.

For oral maintenance in schizophrenia, a common starting range is 0.5 to 5 mg once or twice daily, moving to a usual maintenance range of 5 to 20 mg per day. For long-acting injectable use, haloperidol decanoate is typically 50 to 200 mg intramuscularly every 4 weeks, given by a clinician. For acute agitation, a common dose is 2 to 5 mg by intramuscular or intravenous injection, repeated per protocol. The prescriber sets and adjusts the dose based on response, side effects, and other medications.

Safety monitoring

• Movement effects (EPS) and involuntary-movement screen. Ask about stiffness, tremor, and restlessness at every early visit. An AIMS (Abnormal Involuntary Movement Scale) screen every six months is important because haloperidol has the highest tardive dyskinesia risk in the class.
• ECG. A baseline ECG and periodic checks are appropriate, especially when haloperidol is given intravenously or at higher doses. QTc prolongation with IV haloperidol is well documented and clinically important.
• Prolactin. Check if a person develops symptoms such as breast changes, milk production, or menstrual changes.
• Metabolic labs. Weight, BMI, fasting glucose or HbA1c, and lipids at baseline and at least annually. Metabolic effects tend to be small compared with several newer antipsychotics, but they are still worth tracking.
• Blood pressure at baseline and periodically.

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. Haloperidol is a first-generation antipsychotic and is generally metabolically neutral; the guideline recommends metformin if weight rises by more than 3 percent of pre-medication weight or if other cardiometabolic conditions are present.

Typical titration used in the guideline: 500 mg once daily → 500 mg twice daily after one week → 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

Most people get some side effects. The common ones include:

• Parkinsonism, stiffness, slowness, tremor, and a shuffling walk. This looks like Parkinson's disease and improves when the dose is lowered or another medication is added.
• Akathisia, restlessness and an inability to sit still.
• Acute dystonia, sudden, painful muscle spasms, most often in the neck, jaw, tongue, or eyes. This can be frightening; it is treatable and usually reversible with medication.
• Sedation at higher doses.
• Raised prolactin, which can cause breast changes, milk production, or menstrual changes.

If a side effect is severe, or it is not improving, that is a conversation to have with the prescriber rather than a reason to stop on your own.

Serious side effects and warnings

Serious problems are uncommon, but a few are worth knowing.

Boxed warning. Like all antipsychotics, haloperidol carries an FDA boxed warning that it increases the risk of death in older adults with dementia-related psychosis, and antipsychotics are not approved for that use. Any decision to use haloperidol in an older person with dementia, including for short-term agitation, involves an explicit conversation about that increased risk.

• Tardive dyskinesia. A movement disorder linked to long-term antipsychotic use, involving repetitive involuntary movements, often of the face, tongue, or mouth. Haloperidol carries the highest tardive dyskinesia risk among commonly used antipsychotics, and the risk rises with longer use and higher doses.
• Neuroleptic malignant syndrome. A rare but serious reaction. Signs include high fever, muscle stiffness, confusion, and an unstable heartbeat or blood pressure. It is a medical emergency.
• QTc prolongation. Haloperidol, and especially intravenous haloperidol, can prolong the QTc interval on an ECG, which raises the risk of dangerous heart rhythms. Baseline and follow-up ECGs are important, particularly with parenteral use, and combining haloperidol with other QTc-prolonging medications should be discussed with the prescriber.
• Acute dystonic reactions. These can be frightening but are treatable and usually reversible with a dose of medication such as diphenhydramine or benztropine.

This is not medical advice. Any concern about a serious side effect should be discussed with a prescriber promptly.

Sexual side effects

Haloperidol can affect sex drive, arousal, or function. Some of that is related to raised prolactin. If sexual side effects appear, it is worth raising with a prescriber rather than living with it, because dose changes or a switch to another medication may help.

Weight, appetite, and sleep

Haloperidol is generally lighter on weight than many newer antipsychotics, particularly olanzapine and quetiapine. Weight, blood sugar, and cholesterol are still checked periodically, since effects vary from person to person.

Sedation is possible at higher doses. Some people find haloperidol activating in a way that disrupts sleep, and others find it slightly sedating. If sleep problems persist, that is worth raising with the prescriber.

Starting and dosing basics

This section is general background, not a dosing instruction for any individual. The right dose is a decision for a prescriber. Ranges are typical framework only, not a prescription for any individual.

Haloperidol comes as tablets, an oral concentrate, a short-acting injection (haloperidol lactate) used for acute agitation, and a long-acting injection (haloperidol decanoate) given every four weeks by a clinician. Doses for acute agitation, maintenance treatment, and long-acting injection are different, and the prescriber chooses the right form and dose for the situation. It can be taken with or without food.

Missed doses and interactions

If you miss an oral dose, the general guidance is to take it when you remember, unless it is almost time for the next dose. In that case, skip the missed dose and carry on. Don't take two doses to make up for one. For long-acting injections, the clinic will manage the schedule.

Some medications change how the body processes haloperidol or add to its QTc effect on the heart. Because of that, the prescriber and pharmacist need a full list of your medications and supplements, including over-the-counter ones. Alcohol is not formally prohibited, but it can worsen sedation and other side effects and is generally best limited.

Stopping and tapering

Stopping haloperidol should be gradual and planned with a prescriber. The body adjusts to the medication over time, and stopping suddenly can cause discomfort, movement problems, or a return of the symptoms it was treating. A prescriber can step the dose down over time in a way that fits the situation.

Pregnancy and breastfeeding

This is an area where individual circumstances matter and the decision belongs with a clinician. Untreated schizophrenia and severe agitation carry their own risks during pregnancy, and haloperidol passes into breast milk. Anyone who is pregnant, planning a pregnancy, or breastfeeding should talk it through with their prescriber so the specific risks and benefits can be weighed for their situation. This is not medical advice.

Cost and generic availability

Haloperidol has been available as a generic for decades and is one of the least expensive antipsychotics. Both the oral tablets and the injectable forms are widely stocked. Most insurance plans cover it without difficulty, and cash prices for oral haloperidol tend to be very low. That cost profile is one reason haloperidol remains important in resource-limited settings and in acute care.

Common questions

Why is haloperidol still used? It is effective, inexpensive, widely available, and has decades of clinical experience behind it. It works quickly for acute agitation, and it comes in a long-acting injection that helps some people stay well without needing to remember pills. It is not usually a first choice for maintenance today, mostly because of movement side effects, but it remains an important option.

What is tardive dyskinesia? Tardive dyskinesia is a movement disorder that can develop after long-term antipsychotic use. It usually involves repetitive involuntary movements, often of the face, tongue, or mouth. Haloperidol carries the highest risk in the class. Regular screening with the AIMS test helps catch it early, when there are more treatment options.

Why is haloperidol lighter on metabolic side effects? Because it is relatively selective for the dopamine D2 receptor and does not act strongly at histamine, muscarinic, or serotonin receptors that other antipsychotics use, it does not drive appetite, weight, or metabolic changes as much. That does not mean the risk is zero, weight and labs are still checked, but it tends to be favorable.

What are dystonic reactions? Dystonic reactions are sudden, painful muscle spasms, most often in the neck, jaw, tongue, or eyes. They can be frightening, but they are usually reversible with a single dose of a treating medication such as diphenhydramine or benztropine. They are more common early in treatment, especially with higher doses.

Questions to ask your prescriber

• What are we hoping this treats, and how will we know it's working?
• Which side effects should I expect early, and which ones should I call about?
• What should I watch for in terms of stiffness, tremor, or restlessness?
• Would a long-acting injection be a better fit for me than a daily pill?
• If we decide to stop it later, how would we do that safely?

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. Prescribing information (DailyMed).
• MedlinePlus, U.S. National Library of Medicine.
• National Institute of Mental Health.
• American Psychiatric Association. Practice Guideline for the Treatment of Patients with Schizophrenia, 3rd edition.
• National Institute for Health and Care Excellence (NICE). CG178, Psychosis and schizophrenia in adults.
• American Diabetes Association / American Psychiatric Association. Consensus Statement on Antipsychotic Drugs and Obesity and Diabetes.
• 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.