Resperidone

# Resperidone ## Overview - **Classification**: Atypical antipsychotic (second-generation) - **Mechanism**: Potent antagonist of D2 (dopamine) and 5-HT2A (serotonin) receptors. Also antagonizes alpha1-adrenergic, H1-histaminergic, and alpha2-adrenergic receptors. ## Primary Indications 1. **Schizophrenia** - Treatment of acute and maintenance phases. 2. **Bipolar I Disorder** - Monotherapy or adjunctive treatment of manic or mixed episodes. 3. **Irritability associated with Autistic Disorder** - Short-term treatment in children and adolescents. ## Adult Dosing ### Standard Dosing **Schizophrenia** - **Dose**: Initial **0.5-1 mg** once or twice daily. - **Frequency**: Once or twice daily. - **Route**: Oral. - **Titration**: Increase by **0.5-1 mg/day** no more frequently than every 24 hours. - **Maintenance**: Typically **2-8 mg/day**. Max recommended **16 mg/day**. **Bipolar I Disorder (Manic/Mixed Episodes)** - **Dose**: Initial **2-3 mg** once daily. - **Frequency**: Once daily. - **Route**: Oral. - **Titration**: Adjust by **1 mg/day** if needed. - **Maintenance**: Typically **1-6 mg/day**. ### Dose Adjustments - **Renal Impairment**: CrCl < 30 mL/min: Initial **0.5 mg** once daily. Titrate slowly. Max **2 mg/day**. - **Hepatic Impairment**: Initial **0.5 mg** once daily. Titrate slowly. Max **2 mg/day**. - **Elderly Patients**: Initial **0.5 mg** twice daily. Increase by **0.5 mg** twice daily. Max **4 mg/day**. Increased risk of orthostatic hypotension and stroke. ## Pediatric Dosing ### Neonates (0-28 days) - **Dose**: **Not recommended**. - **Special Notes**: Safety and efficacy not established in this age group. ### Infants (1-12 months) - **Dose**: **Not recommended**. - **Special Notes**: Safety and efficacy not established in this age group. ### Children (1-12 years) **Irritability associated with Autistic Disorder (approved ≥5 years)** - **Weight < 20 kg**: - **Dose**: Initial **0.25 mg** once daily. - **Frequency**: Once daily. - **Titration**: Increase by **0.25 mg** every 4 days. - **Maximum**: Target **0.5 mg/day**. Max **1.5 mg/day**. - **Weight ≥ 20 kg**: - **Dose**: Initial **0.5 mg** once daily. - **Frequency**: Once daily. - **Titration**: Increase by **0.5 mg** every 4 days. - **Maximum**: Target **1 mg/day**. Max **2.5 mg/day**. - **Special Notes**: Oral solution (**1 mg/mL**) or ODT may aid precise dosing and administration. ### Adolescents (13-18 years) **Schizophrenia (approved ≥13 years)** - **Dose**: Initial **0.5 mg** once daily. - **Frequency**: Once or twice daily. - **Titration**: Increase by **0.5-1 mg/day** at intervals ≥24 hours. - **Target**: **3 mg/day**. - **Maximum**: **6 mg/day**. **Bipolar I Disorder (manic/mixed, approved ≥10 years)** - **Dose**: Initial **0.5 mg** once daily. - **Frequency**: Once daily. - **Titration**: Increase by **0.5-1 mg/day** at intervals ≥24 hours. - **Target**: **1-2.5 mg/day**. - **Maximum**: **6 mg/day**. ## Safety Information ### Contraindications - **Absolute**: Known hypersensitivity to risperidone or any component. - **Absolute**: Not approved for dementia-related psychosis due to increased mortality risk. ### Common Adverse Effects - **Very Common (>10%)**: Insomnia, anxiety, headache, weight gain, somnolence, increased prolactin. - **Common (1-10%)**: Dizziness, extrapyramidal symptoms (EPS), nausea, rhinitis, orthostatic hypotension, fatigue, blurred vision. - **Serious but Rare**: Neuroleptic Malignant Syndrome (NMS), tardive dyskinesia (TD), hyperglycemia/diabetes, cerebrovascular events (elderly with dementia), agranulocytosis, QT prolongation, priapism. ### Key Drug Interactions - **CYP2D6 Inhibitors (e.g., paroxetine)**: May increase risperidone plasma levels. Consider lower risperidone doses. - **CYP3A4 Inducers (e.g., carbamazepine)**: May decrease risperidone active fraction levels. May need to increase risperidone dose. - **Dopamine Agonists (e.g., levodopa)**: Risperidone antagonizes dopamine, potentially reducing efficacy of agonists. - **Antihypertensives**: Additive hypotensive effects. Monitor blood pressure closely. - **CNS Depressants (e.g., alcohol, benzodiazepines)**: Additive sedative effects. Use with caution. - **Drugs that prolong QT interval**: Increased risk of Torsades de Pointes. Avoid co-administration if possible. ## Monitoring & Follow-up - **Before Treatment**: Baseline weight, height, fasting glucose, lipids, blood pressure. ECG if cardiac risk factors. - **During Treatment**: - **Weight/BMI**: Monthly for 3 months, then quarterly. - **Fasting Glucose/Lipids**: At 3 months, then annually. - **Blood Pressure**: As clinically indicated. - **AIMS (Abnormal Involuntary Movement Scale)**: Baseline, then quarterly, to monitor for TD. - **Prolactin**: If symptoms of hyperprolactinemia develop. - **Clinical Signs**: Monitor for EPS, NMS, orthostatic hypotension, sedation, mental status changes. ## Clinical Pearls - 💡 **Tip 1**: Take with food to minimize GI upset. - 💡 **Tip 2**: Advise patients to rise slowly to reduce risk of orthostatic hypotension, especially during titration. - 💡 **Tip 3**: Monitor for hyperprolactinemia (galactorrhea, amenorrhea, gynecomastia, sexual dysfunction). - 💡 **Tip 4**: Oral solution or ODT formulation can be useful for patients with swallowing difficulties or for precise dose adjustments. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.