Risperidone (Risperdal)

What it treats

Risperidone is approved by the U.S. Food and Drug Administration to treat schizophrenia, to treat acute manic or mixed episodes of bipolar I disorder, and for irritability associated with autism spectrum disorder in children and adolescents. It is also used, off-label, for a range of related conditions including some behavioral disturbances of dementia, though as with all antipsychotics, that use is bounded by the boxed warning for older adults with dementia.

Risperidone is often chosen when a dependable and well-characterized antipsychotic is needed at moderate cost. It is not usually the first choice when a person has strong reasons to avoid prolactin elevation or movement side effects.

How it works

Risperidone is an atypical antipsychotic. It blocks dopamine and serotonin receptors most centrally, and it affects other receptors at higher doses. That combined action reduces psychotic symptoms and settles manic symptoms over days to weeks.

An important detail: risperidone is broken down in the body to an active metabolite called paliperidone, which is itself sold as a separate medication (Invega). Effects in a given person depend partly on how their body handles that conversion.

Receptor mechanism (detail)

Risperidone is a potent 5-HT2A and D2 antagonist. At higher doses it also blocks α1-adrenergic, α2-adrenergic, and H1 histamine receptors. Its main active metabolite, paliperidone (9-hydroxyrisperidone), shares much of the same receptor profile and does much of the clinical work. The relatively strong D2 blockade explains why risperidone is more likely than several other atypicals to cause extrapyramidal side effects, parkinsonism, akathisia, at higher doses, and why it raises prolactin more than most other atypicals. The 5-HT2A blockade softens some of that effect at lower doses.

Potency and typical dosing pattern

Ranges are typical framework only, not a prescription for any individual. Risperidone is moderate to high potency by milligram, small doses do meaningful work.

Oral risperidone typically starts at 1 to 2 mg per day, adjusted upward to a maintenance range of 4 to 8 mg per day, with a maximum of 16 mg per day in the prescribing information. Doses at the upper end come with more extrapyramidal side effects. Long-acting injectable options include Risperdal Consta, given intramuscularly at 25 to 50 mg every 2 weeks (with an oral overlap for the first three weeks while the injection reaches steady state), and Perseris, a subcutaneous once-monthly form. Long-acting forms are useful when adherence to daily oral dosing is difficult.

Safety monitoring

• Metabolic labs. Weight and BMI at baseline, weeks 4, 8, and 12, then quarterly. Fasting glucose or HbA1c and a lipid panel at baseline, three months, and at least annually. Risperidone's metabolic risk is moderate, lower than olanzapine and clozapine, higher than aripiprazole.
• Prolactin. Risperidone raises prolactin more than most other atypicals. Ask about galactorrhea (breast milk production not related to childbirth), amenorrhea (missed periods), gynecomastia (breast tissue development), and sexual dysfunction at follow-up. Check a prolactin level if any of those are present.
• Movement effects. Akathisia and parkinsonism are more common at higher doses. Ask at every early visit. AIMS every six months looks for tardive dyskinesia over the long term.
• Blood pressure at baseline and periodically, including orthostatic checks in older adults.

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. Risperidone is classified as medium-risk in the guideline; metformin co-commencement is recommended when other cardiometabolic conditions are present, and metformin should be started if weight rises by more than 3 percent of pre-medication weight.

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 experience some side effects. The common ones include:

• Extrapyramidal effects, parkinsonism (slowed movement, stiffness, tremor) and akathisia (restlessness).
• Prolactin-related effects, menstrual irregularity, breast tenderness or milk production, sexual difficulty.
• Sedation, especially early.
• Weight gain.
• Dizziness, especially on standing.
• Mild increase in appetite.

Movement effects and prolactin effects are the two most likely reasons a prescriber lowers the dose, changes the timing, or switches to a different antipsychotic. Both are worth reporting rather than tolerating quietly.

Serious side effects and warnings

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

Boxed warning. Like all antipsychotics, risperidone 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.

• Tardive dyskinesia. A movement disorder linked to long-term antipsychotic use, involving repetitive involuntary movements, often of the face or mouth. The risk rises with longer use and with higher doses.
• Neuroleptic malignant syndrome. A rare but serious reaction. Signs include high fever, muscle stiffness, confusion, and unstable heart rate or blood pressure. It is a medical emergency.
• Metabolic effects. Weight gain, hyperglycemia, and dyslipidemia are all monitored over time. Risperidone's risk is moderate, not negligible.
• Orthostatic hypotension and falls, particularly during initial titration and in older adults.
• Hyperprolactinemia. Sustained high prolactin can affect menstrual cycles, fertility, sexual function, and, over long periods, bone health.

Sexual side effects

Sexual side effects are more common with risperidone than with several other atypicals, largely because of prolactin elevation. Lower desire, difficulty with arousal or orgasm, and erectile difficulty can occur. If they occur and are bothersome, that is worth raising with the prescriber rather than living with it, because there are usually options, a dose reduction, a switch to a lower-prolactin antipsychotic, or occasionally the addition of another medication. This is not medical advice.

Weight, appetite, and sleep

Weight gain is possible with risperidone. It tends to sit between the low-weight-effect medications like aripiprazole and the higher-weight-effect medications like olanzapine and clozapine. Under the Carolan guideline it is classified as medium-risk, meaning routine metformin co-commencement is not automatic but is recommended if other cardiometabolic conditions are present, or if weight rises by more than 3 percent from baseline. Weight, blood sugar, and lipids are tracked over time.

Sedation is common early, but risperidone is not as strongly sedating as olanzapine or quetiapine. Timing of the dose can be adjusted based on how it affects sleep and daytime alertness.

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.

Risperidone comes as tablets, orally disintegrating tablets (M-Tabs), an oral solution, and long-acting injectable forms (Risperdal Consta, Perseris) given by a clinician. It can be taken with or without food. Prescribers tend to keep the daily dose in the lower part of the range when possible, because side effects, particularly extrapyramidal and prolactin effects, rise sharply at higher doses.

Missed doses and interactions

If you miss a 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.

Some medications change how the body processes risperidone. Strong CYP2D6 inhibitors and certain other drugs can raise risperidone levels; enzyme inducers can lower them. 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 can worsen sedation and orthostasis and is generally best limited.

Stopping and tapering

Stopping risperidone should be gradual and planned with a prescriber. The body adjusts to the medication over time, and stopping suddenly can cause discomfort or a return of the underlying symptoms. 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 bipolar disorder and psychosis carry their own risks during pregnancy, and risperidone also 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.

Cost and generic availability

Risperidone has been available as a generic for years and is inexpensive. The brand name Risperdal and generic risperidone contain the same active medication and work the same way. The long-acting injectable forms cost significantly more than oral tablets. Most insurance plans cover the generic tablets.

Common questions

Why does risperidone raise prolactin? Risperidone strongly blocks dopamine D2 receptors, including those in a part of the brain (the tuberoinfundibular pathway) where dopamine normally holds prolactin release in check. When that dopamine signal is blocked, prolactin rises. Among the atypical antipsychotics, risperidone raises prolactin the most, together with its metabolite paliperidone.

What is the difference between risperidone and paliperidone? Paliperidone (Invega) is the main active metabolite of risperidone, it is what the body converts risperidone into. As a standalone medication, paliperidone skips the conversion step, which can matter for people whose metabolism handles that step unusually fast or slow. Both share most of the receptor profile and side-effect pattern, including the tendency to raise prolactin.

Should I take metformin with it? The Carolan guideline classifies risperidone as medium-risk, so metformin is not automatically co-commenced. It is recommended when other cardiometabolic conditions are present at the start, or if weight rises by more than 3 percent of pre-medication weight during treatment. Whether that fits your situation is a decision to make with your prescriber.

What is akathisia? Akathisia is a feeling of restlessness and an inability to sit still, often with an urge to keep moving. It is a common side effect of risperidone, especially at higher doses. It is treatable, so it is worth reporting to the prescriber early.

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?
• Should we check a prolactin level if I notice specific symptoms?
• How will we track weight, blood sugar, and lipids?
• 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. Guidelines and prescribing information reviewed and current as of June 8, 2026.

• U.S. Food and Drug Administration. Risperidone (Risperdal) prescribing information (DailyMed).
• MedlinePlus, U.S. National Library of Medicine. Risperidone.
• National Institute of Mental Health. Mental health medications.
• 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.