A 4-year-old girl with autism spectrum disorder and moderate intellectual disability presents with severe irritability, frequent tantrums, and aggressive behaviour towards peers and caregivers. Behavioural interventions have been partially effective. Which is the drug of choice for managing irritability and aggression in this child?

Explanation

## Pharmacotherapy for Irritability and Aggression in ASD **Key Point:** Risperidone is the first-line and FDA-approved atypical antipsychotic for irritability, aggression, and self-injurious behaviour in children with autism spectrum disorder. ### FDA Approval & Evidence Base - Risperidone is one of only two medications (along with aripiprazole) with FDA approval specifically for irritability in ASD - Approved for children aged 5–16 years with ASD - Robust evidence from randomized controlled trials showing 50–60% reduction in irritability and aggression scores - Effect size is larger for irritability than for core autism symptoms ### Mechanism of Action Risperidone is an atypical antipsychotic that blocks dopamine D~2~ and serotonin 5-HT~2A~ receptors. This combination reduces impulsivity, aggression, and emotional dysregulation while having lower extrapyramidal side effect risk compared to first-generation antipsychotics. ### Dosing in Pediatric ASD - Initial dose: 0.25–0.5 mg/day (lower in younger or smaller children) - Target range: 0.5–2 mg/day in divided doses - Titrate slowly over 1–2 weeks to minimize side effects - Maximum: 3–4 mg/day (rarely needed) **High-Yield:** Risperidone is preferred over other antipsychotics in ASD because it has the strongest evidence base and lowest rates of sedation compared to quetiapine or chlorpromazine. ### Monitoring Requirements - **Metabolic:** Weight, BMI, fasting glucose, lipid panel at baseline and regularly (risk of weight gain and metabolic syndrome) - **Neurological:** Monitor for tardive dyskinesia, parkinsonism, akathisia - **Cardiac:** ECG if family history of sudden cardiac death or prolonged QT - **Prolactin:** May elevate; monitor for gynecomastia or galactorrhoea **Clinical Pearl:** Children with ASD often have sensory sensitivities and may be more sensitive to medication side effects. Start low, go slow, and monitor closely for unexpected reactions. ### Common Side Effects - Weight gain (most common; 30–50% of children) - Sedation (usually transient) - Increased appetite - Tremor, rigidity (less common than with older antipsychotics) **Warning:** Do NOT use risperidone for ADHD symptoms alone or for core autism deficits (social communication, restricted interests). It is specifically indicated for irritability-related behaviours. [cite:DSM-5 p 53–54; FDA Approval for Risperidone in ASD; American Academy of Pediatrics]