An 18‑year‑old male recently started on divalproex sodium 500 mg twice daily and risperidone 1 mg in the morning and 2 mg at night presents with acute cervical dystonia (torticollis) after missing today’s doses; what immediate treatment is indicated and is this reaction a side effect of the medications?

Immediate Treatment for Acute Risperidone-Induced Torticollis

Administer benztropine 1–2 mg intramuscularly or intravenously immediately—this acute dystonic reaction will resolve within minutes and represents a medical emergency that requires prompt anticholinergic therapy. 1, 2, 3

Understanding This Reaction

Your patient is experiencing acute drug-induced dystonia (torticollis), a well-established adverse effect of risperidone that occurs through dopamine D2 receptor blockade in the nigrostriatal pathway. 1, 2 This is absolutely a medication side effect—young males are at the highest risk for acute dystonia, particularly within the first few days of antipsychotic initiation. 1, 2, 3

The fact that he missed today's doses is irrelevant to causation; acute dystonia typically manifests within the first 4 days of treatment or after dose changes, and your patient is within that critical window. 2, 4

Immediate Pharmacologic Management

First-Line Treatment

• Benztropine 1–2 mg IM or IV provides the most rapid relief, with improvement often visible within minutes 1, 2, 3
• Expect complete resolution within 30–60 minutes 2

Alternative if Benztropine Unavailable

• Diphenhydramine 25–50 mg IM or IV offers equivalent efficacy for acute dystonic reactions 1, 2, 3
• Use the same dosing route (IM or IV) for rapid onset 3

Critical Post-Treatment Management

Continuation Therapy

After the acute episode resolves, continue oral anticholinergic therapy for 48–72 hours minimum to prevent recurrence:

• Benztropine 1–2 mg orally twice daily, OR 1
• Diphenhydramine 25–50 mg orally every 6 hours 1

The anticholinergic must be maintained even after symptoms resolve because dystonia can recur as the acute dose wears off. 1

Medication Adjustment Required

You cannot simply restart risperidone at the current dose (1 mg morning, 2 mg evening) without addressing the dystonia risk. 1, 2 Choose one of these strategies:

1. Reduce risperidone dose significantly (e.g., to 0.5 mg twice daily) and titrate slowly while maintaining anticholinergic coverage 1, 3

2. Switch to a lower-EPS-risk atypical antipsychotic such as quetiapine, olanzapine, or clozapine, which have substantially lower dystonia rates 1, 3

3. Continue current risperidone dose ONLY if you provide prophylactic anticholinergic therapy for at least 2–4 weeks, then attempt gradual withdrawal 1

Why This Happened

Risperidone carries dose-dependent extrapyramidal symptom risk that is higher than other atypical antipsychotics. 1 At his current total daily dose of 3 mg, this 18-year-old male hit multiple high-risk factors:

• Young age (highest risk group) 1, 2, 3
• Male gender (2–3× higher risk than females) 1, 2
• First few days of treatment (90% of acute dystonia occurs in days 1–5) 2, 4
• Risperidone specifically (higher EPS risk than quetiapine/olanzapine/clozapine) 1

Critical Safety Monitoring

Watch for Life-Threatening Progression

While treating, monitor continuously for laryngeal dystonia, which presents as:

• Choking sensation 1
• Stridor or difficulty breathing 1
• Inability to swallow 2

Laryngeal involvement is a medical emergency requiring immediate airway management in addition to anticholinergics. 2

Contraindications to Anticholinergics

Before administering benztropine or diphenhydramine, quickly screen for:

• Acute angle-closure glaucoma 2, 3
• Severe benign prostatic hypertrophy with urinary retention 2, 3
• Known anticholinergic drug intoxication (unlikely here but critical to exclude) 2

If any contraindication exists, immediate psychiatric consultation is required for alternative dystonia management. 2

Common Pitfall to Avoid

Do NOT interpret this dystonia as anxiety, malingering, or voluntary behavior. 3 Acute dystonia is frequently misdiagnosed in emergency settings, leading to:

• Inappropriate psychiatric admission for "behavioral issues" 3
• Dose escalation of the offending antipsychotic (catastrophic error) 3
• Patient refusal of future psychiatric treatment due to traumatic experience 2

The fact that you can temporarily relieve his symptoms with manual pressure and positioning does not make this voluntary—it demonstrates the muscular nature of dystonia and the effectiveness of physical countermaneuvers that patients instinctively discover. 2

Disposition and Follow-Up

After acute treatment:

• Observe for at least 2 hours to ensure no recurrence as the anticholinergic peaks 1
• Provide a 3–5 day supply of oral anticholinergic with explicit instructions to take it even if asymptomatic 1
• Urgent psychiatry follow-up within 24–48 hours to reassess the risperidone regimen 1, 3
• Document this reaction prominently in the medical record as a significant adverse drug event 2

The divalproex is not contributing to this dystonia—mood stabilizers do not cause acute dystonic reactions. 1, 2