Risperidone ๐
Always check the BNF link here for full prescribing guidance.
- ๐ Risperidone is an atypical antipsychotic (second-generation).
- Used in both psychiatric illness (schizophrenia, bipolar) and behavioural disturbance in dementia (short-term only).
โ๏ธ Mode of Action
- Antagonist at dopamine Dโ receptors โ antipsychotic effect (reduces positive symptoms of schizophrenia).
- Antagonist at serotonin 5-HTโA receptors โ helps with negative symptoms and fewer extrapyramidal side effects compared to typical antipsychotics.
- Also blocks ฮฑโ-adrenergic and histamine (Hโ) receptors โ sedation, hypotension, weight gain.
๐ Indications
- ๐ง Schizophrenia (acute and maintenance treatment).
- ๐ Acute mania in bipolar disorder.
- ๐ต Short-term treatment of persistent aggression in moderate-to-severe Alzheimerโs dementia (max 6 weeks, lowest dose possible).
- May be used off-label in challenging behaviour, learning disability, or agitation (specialist decision).
๐ Dose (examples โ check BNF/local guidance)
- ๐ต Aggression in dementia: 250โ500 mcg BD (max 1 mg BD).
- ๐ฐ Acute anxiety/agitation: 2 mg daily โ titrate up to 6 mg daily. Dispersible tablets useful if tablets may be spat out.
- ๐ Ongoing anxiety/agitation: 1โ2 mg BD PO. In elderly, start at 500 mcgโ1 mg BD.
- ๐ Available tablet strengths: 0.25 mg, 1 mg, 2 mg (also liquid and depot injections for long-term use).
๐ Interactions
- Reduce dose in renal/hepatic impairment.
- Multiple CYP2D6-mediated interactions (e.g. fluoxetine, paroxetine โ risperidone levels).
- Other CNS depressants โ sedation.
- QT-prolonging drugs โ arrhythmia risk.
โ Contraindications / Cautions
- โ Phenylketonuria (due to aspartame in oral solution).
- โ ๏ธ Caution in elderly with dementia (โ risk of stroke, mortality).
- โ ๏ธ Parkinsonโs disease or Lewy body dementia (worsens motor symptoms, โ sensitivity).
- โ ๏ธ Prolonged QT, cardiovascular disease.
โ ๏ธ Side Effects
- ๐ฉบ Cardiac: Hypotension, arrhythmias, prolonged QT, โ stroke risk in elderly.
- ๐ง CNS: Drowsiness, dizziness, extrapyramidal symptoms (tremor, rigidity), akathisia, tardive dyskinesia.
- โ๏ธ Metabolic: Weight gain, hyperglycaemia, โ cholesterol/triglycerides.
- ๐ฉธ Endocrine: โ prolactin โ galactorrhoea, menstrual irregularities, sexual dysfunction.
- Other: Constipation, dry mouth, blurred vision.
๐ Clinical Pearls
- Monitor weight, glucose, lipids, BP at baseline and during treatment.
- ECG if cardiovascular risk factors (QT prolongation risk).
- In dementia, use for the shortest possible duration at the lowest effective dose.
- Consider depot/long-acting injection for non-adherence in schizophrenia.
๐ References
