Risperidone side effects: what's common, what's serious, what to do

Risperidone is one of the more tolerable antipsychotics at low to moderate doses, which is part of why it's so widely prescribed. But it does have a distinctive side effect profile, and a few of those side effects — particularly hyperprolactinaemia — are commonly missed in clinical practice.

Common side effects (and what to do)

Sedation and fatigue

Common in the first 1–4 weeks. Usually improves significantly. If it doesn't:

• Take the dose at bedtime if you're not already
• Avoid combining with other sedating medications or alcohol
• Talk to your prescriber about a slight dose reduction

Orthostatic hypotension

Dizziness when standing up, especially during titration. Usually resolves. Stand up slowly, stay hydrated, and let your prescriber know if you faint or are still dizzy after 2 weeks.

Weight gain

Average 2–3 kg in the first year — less than olanzapine or clozapine, but still meaningful. Lifestyle support, monitoring of glucose and lipids, and (sometimes) metformin all apply. See our weight gain management guide.

Nausea and constipation

Mild GI symptoms are common in the first few weeks and usually settle.

Movement-related side effects (extrapyramidal symptoms)

Risperidone is more likely than other second-generation antipsychotics to cause movement-related side effects, especially at doses above 6 mg/day.

Akathisia

An intense inner restlessness — a feeling that you can't sit still, that you have to keep moving. Easy to misread as anxiety. Akathisia is one of the most distressing side effects and can lead to medication non-adherence or even suicide if not addressed.

What helps:

• Tell your prescriber immediately
• Lowering the dose often helps
• Beta-blockers (especially propranolol) work well
• Benzodiazepines short-term
• Switching to a lower-EPS antipsychotic if it persists

Parkinsonism

Stiffness, slowness, masked facial expression, tremor. Looks like Parkinson's disease and is caused by the dopamine blockade. Reversible by lowering the dose or switching medications. Anticholinergics like benztropine can help short-term.

Acute dystonia

Sudden muscle contractions, often in the neck, jaw, or eyes (oculogyric crisis). More common in young men, in the first few days of treatment. Frightening but treatable — IM benztropine or diphenhydramine reverses it within minutes.

Tardive dyskinesia

The most concerning long-term movement side effect — involuntary repetitive movements (especially of the face, mouth, and tongue) that can persist or become permanent. Risk increases with cumulative dose and duration. Annual screening with the AIMS (Abnormal Involuntary Movement Scale) is recommended for any patient on a long-term antipsychotic. See our TD guide.

Hyperprolactinaemia — the often-missed side effect

Risperidone raises prolactin (a pituitary hormone) more than almost any other modern antipsychotic. Yet many patients never have their prolactin checked, and the symptoms get attributed to other causes.

Symptoms in women:

• Irregular or absent periods
• Galactorrhea (milk discharge from breasts unrelated to pregnancy or breastfeeding)
• Reduced libido
• Difficulty getting pregnant
• Long-term: reduced bone density (osteoporosis risk)

Symptoms in men:

• Reduced libido
• Erectile dysfunction
• Gynecomastia (breast enlargement)
• Galactorrhea (less common but possible)
• Long-term: reduced bone density

What to do:

• Ask for a prolactin level check at baseline and if any symptoms appear
• If high and symptomatic, options include lower dose, switching to a prolactin-sparing antipsychotic (aripiprazole, ziprasidone, lurasidone), or adding low-dose aripiprazole as an adjunct
• Have bone density (DEXA scan) considered if prolactin is persistently elevated for years

Sexual side effects

Common but often unspoken. Causes include the prolactin elevation above plus the direct dopaminergic and serotonergic effects on sexual function. Strategies:

• Talk to your prescriber — many patients never raise this and quietly stop their medication because of it
• Dose reduction often helps
• Switch to a more sex-neutral antipsychotic (aripiprazole, brexpiprazole)
• Sildenafil/tadalafil for erectile difficulty

Less common but serious effects

• Neuroleptic Malignant Syndrome (NMS) — rare, life-threatening reaction with high fever, severe rigidity, autonomic instability, altered consciousness. Requires emergency care. Stop the medication immediately.
• Diabetic ketoacidosis — rare but reported, especially in patients with new-onset diabetes on antipsychotics
• Stroke risk in elderly with dementia — FDA black box warning
• Allergic reactions / DRESS syndrome — very rare, can be severe

The big picture

For most patients, risperidone at low to moderate doses is tolerable and effective. The keys to long-term success are:

• Use the lowest effective dose
• Check prolactin if any sexual or menstrual symptoms appear
• Annual screening for tardive dyskinesia
• Active management of weight and metabolic factors
• Open communication with your prescriber about side effects — including the embarrassing ones

This article is for educational purposes only and is not medical advice. Information is summarised from publicly available FDA labelling. Always consult your prescribing clinician before starting, stopping, or changing any medication.