Usage
Risperidone is an atypical antipsychotic primarily prescribed for the treatment of schizophrenia, bipolar disorder, and irritability associated with autistic disorder in children and adolescents. It is also used for short-term treatment of agitation associated with dementia in Alzheimer’s disease.
Alternate Names
Risperidone is known internationally by the same name. Brand names include Risperdal, Risperdal Consta, Risperdal M-Tabs, Rykindo, Perseris, and Uzedy.
How It Works
Pharmacodynamics: Risperidone acts as a serotonin-dopamine antagonist. It has high affinity for serotonin 5-HT2A and dopamine D2 receptors. It also binds to alpha1-adrenergic and, to a lesser extent, histamine H1 and alpha2-adrenergic receptors. The therapeutic effects in schizophrenia and bipolar mania are believed to be mediated primarily through antagonism at serotonin 5-HT2A and dopamine D2 receptors.
Pharmacokinetics:
- Absorption: Risperidone is well absorbed orally. Food does not significantly affect absorption.
- Metabolism: Extensively metabolized in the liver, primarily by CYP2D6 to the active metabolite 9-hydroxyrisperidone (paliperidone).
- Elimination: Excreted in urine and feces. The elimination half-life is approximately 3 hours for risperidone and 24 hours for 9-hydroxyrisperidone.
Mode of Action: Risperidone binds to and blocks serotonin 5-HT2A and dopamine D2 receptors in the brain. This action helps regulate the neurochemical imbalances associated with schizophrenia, bipolar disorder, and autism spectrum disorder. The combined serotonin-dopamine antagonism results in a lower propensity for extrapyramidal side effects compared with typical antipsychotics.
Dosage
Standard Dosage
Adults:
- Schizophrenia: Initially 2 mg/day, increasing to 4 mg/day on the second day. May be further adjusted in 1-2 mg increments every 24 hours or more, up to a usual target dose of 4-6 mg/day. Maximum dose: 16 mg/day.
- Bipolar Mania: Initially 2-3 mg/day. May be increased in 1 mg increments every 24 hours, up to a maximum of 6 mg/day.
- Agitation in Alzheimer’s Dementia: Initially 0.25 mg twice daily. May be increased by 0.25 mg twice daily every other day, up to a maximum of 1 mg twice daily. Duration of therapy should not exceed 6 weeks.
- `<20 kg:** Initially 0.25 mg/day, increasing in 0.25 mg increments every 2 weeks as needed, not to exceed 1 mg/day.
- ≥20 kg: Initially 0.5 mg/day, increasing in 0.5 mg increments every 2 weeks as needed, not to exceed 2.5 mg/day.
Special Cases:
- Elderly Patients: Initiate at a lower dose (e.g., 0.5 mg twice daily) and titrate slowly.
- Patients with Renal Impairment: Lower starting dose and slower titration are recommended.
- Patients with Hepatic Dysfunction: Lower starting dose and slower titration may be necessary.
- Patients with Comorbid Conditions: Dosage adjustments may be required depending on the specific comorbidity (e.g., diabetes, cardiovascular disease).
Clinical Use Cases
Risperidone is not typically used for intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations like status epilepticus or cardiac arrest. It is primarily used for long-term management of psychiatric disorders.
Dosage Adjustments
Dosage adjustments should be made based on patient response, tolerability, and the presence of renal or hepatic impairment. Concomitant medications, particularly CYP2D6 inhibitors or inducers, may necessitate dosage adjustments.
Side Effects
Common Side Effects:
Insomnia, anxiety, agitation, headache, extrapyramidal symptoms (e.g., parkinsonism, dystonia, akathisia), drowsiness, dizziness, weight gain, nausea, constipation.
Rare but Serious Side Effects:
Neuroleptic malignant syndrome (NMS), tardive dyskinesia, hyperprolactinemia, QT prolongation, orthostatic hypotension, seizures, agranulocytosis.
Long-Term Effects:
Tardive dyskinesia, metabolic syndrome, weight gain, hyperprolactinemia.
Contraindications
Hypersensitivity to risperidone.
Drug Interactions
Drugs that inhibit or induce CYP2D6 can affect risperidone levels. Concomitant use with other central nervous system depressants can increase the risk of sedation. Risperidone can potentiate the effects of antihypertensive medications.
Pregnancy and Breastfeeding
Pregnancy Safety Category: C. Risperidone should be used during pregnancy only if the potential benefit outweighs the potential risk to the fetus. Risperidone is excreted in breast milk; caution is advised when administering to breastfeeding women.
Drug Profile Summary
- Mechanism of Action: Serotonin-dopamine antagonist.
- Side Effects: Extrapyramidal symptoms, drowsiness, weight gain, hyperprolactinemia, NMS, tardive dyskinesia.
- Contraindications: Hypersensitivity to risperidone.
- Drug Interactions: CYP2D6 inhibitors/inducers, CNS depressants.
- Pregnancy & Breastfeeding: Use with caution. Category C.
- Dosage: Varies by indication and patient factors.
- Monitoring Parameters: Weight, blood pressure, fasting glucose, lipids, extrapyramidal symptoms, prolactin levels, QTc interval.
Popular Combinations
Risperidone is sometimes used in combination with mood stabilizers (e.g., lithium, valproate) in bipolar disorder.
Precautions
Monitor for extrapyramidal symptoms, metabolic changes, and cardiovascular effects. Caution in patients with a history of seizures, cardiovascular disease, or cerebrovascular disease.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Risperidone?
A: Dosage varies depending on the indication, age, and patient factors. See detailed dosage information above.
Q2: What are the common side effects of Risperidone?
A: Common side effects include insomnia, anxiety, agitation, headache, extrapyramidal symptoms, drowsiness, dizziness, weight gain, nausea, and constipation.
Q3: How does Risperidone differ from other antipsychotics?
A: Risperidone is an atypical antipsychotic with a lower risk of extrapyramidal side effects compared to typical antipsychotics.
Q4: Can Risperidone be used in children?
A: Yes, risperidone is approved for use in children and adolescents for irritability associated with autism.
Q5: What are the serious side effects of Risperidone?
A: Serious side effects include neuroleptic malignant syndrome, tardive dyskinesia, QT prolongation, and seizures.
Q6: What should be monitored in patients taking Risperidone?
A: Monitor weight, blood pressure, fasting glucose and lipids, extrapyramidal symptoms, and prolactin levels. QTc interval should also be monitored.
Q7: What are the drug interactions with Risperidone?
A: Drugs that affect CYP2D6 activity can alter risperidone levels. Concurrent use of CNS depressants can increase sedation.
Q8: Can Risperidone be used during pregnancy?
A: Risperidone is Pregnancy Category C. Use only if the benefit outweighs the risk.
Q9: Is Risperidone safe for breastfeeding mothers?
A: Risperidone is excreted in breast milk. Caution is advised.
