Generic Name

Risperidone

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Classification

FDA Approved Indications

• Schizophrenia
• Bipolar Disorder (Manic or Mixed Episodes)
• Irritability associated with Autistic Disorder

Mechanism of Action

Risperidoneworks by antagonizing dopamine D2 receptors and serotonin 5-HT2A receptors in the brain, which helps modulate neurotransmission involved in psychotic and mood disorders.

Dosage and Administration

Adult: Initial: 1 mg twice daily; titrate based on response and tolerability up to 16 mg/day in divided doses.

Pediatric: Dosing varies; typically, 0.5 mg to 3 mg twice daily, adjusted based on clinical response.

Geriatric: Start at lower doses (e.g., 0.25-0.5 mg twice daily), titrate cautiously.

Renal Impairment: No specific dose adjustment recommended, but caution advised.

Hepatic Impairment: Start at lower doses; titrate cautiously, monitoring for side effects.

Pharmacokinetics

Absorption: Well absorbed orally, with peak plasma concentrations in about 1-2 hours.

Distribution: Extensively bound to plasma proteins (~90%).

Metabolism: Primarily metabolized in the liver via CYP2D6 and CYP3A4 enzyme pathways.

Excretion: Metabolites are excreted primarily in the urine and feces.

Half Life: Approximately 20 hours for the parent drug; longer for risperidone conjugates.

Contraindications

• hypersensitivity to risperidone or its components
• concomitant use of other drugs that prolong QT interval

Precautions

• Increased mortality in elderly patients with dementia-related psychosis
• Risk of metabolic syndrome (weight gain, hyperglycemia, dyslipidemia)
• Monitor for tardive dyskinesia, orthostatic hypotension, neuroleptic malignant syndrome
• Caution in hepatic and renal impairment

Adverse Reactions - Common

• Extrapyramidal symptoms (Common)
• Weight gain (Common)
• Somnolence (Common)
• Dizziness (Common)

Adverse Reactions - Serious

• Neuroleptic Malignant Syndrome (Rare)
• QT prolongation (Uncommon)
• Tardive Dyskinesia (Less common)
• Hyperglycemia/Diabetes Mellitus (Uncommon)

Drug-Drug Interactions

• Other CNS depressants (additive sedative effects)
• Medications prolonging QT interval (e.g., amiodarone, quinidine)
• CYP2D6 and CYP3A4 inhibitors or inducers (affect risperidone levels)

Drug-Food Interactions

• Limited interaction data; monitor for adverse effects if combined with alcohol or CNS depressants

Drug-Herb Interactions

• Potential interactions with herbs affecting CYP enzymes (e.g., St. John’s Wort)

Nursing Implications

Patient/Family Teaching

• Take medication exactly as prescribed; do not stop abruptly.
• Report symptoms of abnormal movements, fever, or muscle rigidity.
• Be aware of potential weight gain, blood sugar, and cholesterol levels.
• Caution about alcohol and operating machinery until effects are known.
• Regular follow-up appointments for monitoring.

Special Considerations

Black Box Warnings:

• Increased mortality in elderly patients with dementia-related psychosis.

Genetic Factors: CYP2D6 poor metabolizers may have increased plasma concentrations.

Lab Test Interference: May increase serum prolactin levels; monitor accordingly.

Overdose Management

Signs/Symptoms: Drowsiness, tachycardia, hypotension, extrapyramidal symptoms, seizures.

Treatment: Supportive care; manage hypotension with IV fluids; monitor cardiac status; consider gastric lavage; activated charcoal may be used if ingestion recent.

Storage and Handling

Storage: Store at room temperature, 20-25°C, protected from moisture and light.

Stability: Stable up to the expiration date on the package under proper storage conditions.