What is the best course of treatment for a 32-year-old female experiencing abnormal movements on one side of her body after a drug reaction?

Management of Unilateral Abnormal Movements After Drug Reaction in a 32-Year-Old Female

Immediately discontinue the offending medication and administer anticholinergic agents (such as diphenhydramine or benztropine) or antihistamines if acute dystonia is suspected, as this represents a potentially reversible drug-induced movement disorder that requires urgent treatment. 1, 2

Immediate Assessment and Stabilization

Identify the Drug-Induced Movement Disorder Type

The unilateral abnormal movements following a drug reaction most likely represent one of four acute extrapyramidal syndromes:

• Acute dystonia: Sudden spastic contractions of distinct muscle groups, often unilateral, occurring within hours to days of drug exposure 1, 2
• Akathisia: Severe restlessness manifesting as pacing or physical agitation 1, 2
• Drug-induced parkinsonism: Rigidity, bradykinesia, and tremor 1
• Tardive dyskinesia: Less likely in acute presentation but characterized by choreoathetoid movements 1, 2

Critical First Steps

• Stop the causative medication immediately if clinically feasible, as this is the primary treatment for all drug-induced dyskinesias 2, 3
• Assess for life-threatening complications: Check for respiratory distress, dysphagia, or laryngeal involvement that could compromise the airway 1
• Rule out metabolic contributors: Check calcium, magnesium, and glucose levels, as hypocalcemia can induce or worsen movement disorders 1

Acute Treatment Protocol

For Acute Dystonia (Most Likely Given Unilateral Presentation)

Administer anticholinergic medications or antihistamines immediately, as these are the first-line treatments for acute dystonic reactions 1:

• Diphenhydramine 25-50 mg IV/IM, or
• Benztropine 1-2 mg IV/IM
• Symptoms typically resolve within 15-30 minutes of treatment 1

For Akathisia

If the presentation suggests akathisia rather than dystonia:

• Lower the antipsychotic dose if the medication must be continued 1
• Consider β-blockers (propranolol) or benzodiazepines if dose reduction is insufficient 1
• Note that antiparkinsonian agents are not consistently helpful for akathisia 1

Diagnostic Workup

Essential Investigations

• Medication history: Identify all recently started or dose-adjusted medications, particularly antipsychotics, antiemetics (metoclopramide, prochlorperazine), or other dopamine antagonists 1
• Metabolic panel: Calcium, magnesium, parathyroid hormone, and thyroid function to exclude hypocalcemia-induced movement disorders 1
• Neuroimaging: Brain MRI if focal neurological signs are present, history of head trauma, or if symptoms don't resolve with medication discontinuation to exclude structural lesions 1
• EEG: If seizure activity is suspected, as seizures can present with unilateral movements 1

Differentiate from Other Causes

Consider alternative diagnoses if drug-induced etiology is unclear:

• Functional neurological disorder: Variable symptoms, entrainability, improvement with distraction 1, 4
• Stroke or TIA: Sudden onset, associated focal deficits, vascular risk factors 1
• Seizure: Altered consciousness, postictal confusion 1
• Chorea from systemic lupus erythematosus: Associated with antiphospholipid antibodies 1

Ongoing Management

If Symptoms Resolve After Drug Discontinuation

• Avoid reintroduction of the offending medication 2, 3
• If antipsychotic therapy is necessary, switch to an atypical antipsychotic with lower extrapyramidal symptom risk (such as quetiapine or clozapine) 1, 2
• Document the reaction clearly in the medical record to prevent future exposure 1

If Symptoms Persist Beyond 2-4 Weeks

• Reassess the diagnosis: Persistent symptoms suggest either tardive dyskinesia or an alternative neurological condition 1, 2
• Neurology consultation: Recommended for persistent or treatment-resistant movement disorders 1
• Consider tetrabenazine for persistent dyskinesia if other measures fail, though this requires careful dose titration and monitoring 5

Prevention and Monitoring

For Future Medication Use

• Use atypical antipsychotics when antipsychotic therapy is required, as they have significantly lower risk of extrapyramidal symptoms compared to typical antipsychotics 1, 2
• Baseline movement assessment: Document any pre-existing abnormal movements before starting medications that can cause dyskinesia 1, 3
• Regular monitoring: If antipsychotics must be continued, assess for dyskinesias every 3-6 months using standardized scales like the Abnormal Involuntary Movement Scale (AIMS) 1, 3

Patient Education

• Inform the patient that withdrawal dyskinesia may occur with medication cessation but typically resolves over time, unlike tardive dyskinesia which may persist 1, 2
• Provide clear instructions to report any new movement symptoms immediately if medications are restarted 1
• Ensure the patient understands which medications to avoid in the future 2

Critical Pitfalls to Avoid

• Do not restart the offending medication to "test" if it was the cause—this risks worsening or perpetuating the movement disorder 2, 3
• Do not use dopamine antagonists (including antiemetics like metoclopramide) for nausea or other symptoms, as these can worsen drug-induced movement disorders 1
• Do not assume symptoms will resolve immediately—acute dystonia responds within minutes to anticholinergics, but other drug-induced movement disorders may take weeks to months to improve after medication discontinuation 1, 2
• Do not overlook hypocalcemia as a contributing factor, especially in patients with parathyroid disorders, recent surgery, or pregnancy 1
• Do not delay treatment while awaiting specialist consultation if acute dystonia is suspected—this is a medical emergency requiring immediate anticholinergic administration 1