What medications can cause parkinsonism?

Medications That Can Cause Parkinsonism

The most common medications that cause drug-induced parkinsonism include antipsychotics (particularly conventional/typical neuroleptics), antiemetics, calcium channel blockers, and certain other classes of drugs that block dopamine receptors. 1, 2

Common Causative Medications

High-Risk Medications

1. Antipsychotic Medications

   • Conventional/Typical Antipsychotics

     • Haloperidol (high potency) 3
     • Chlorpromazine (low potency) 3, 4
     • Thioridazine 3
     • Other phenothiazines 4
     • Butyrophenones 1
     • Thioxanthenes 1

   • Atypical Antipsychotics (lower risk but still possible)

     • Risperidone (highest risk among atypicals) 5
     • Olanzapine 5
     • Note: Quetiapine, clozapine, and pimavanserin have lower risk 3

2. Antiemetics/Gastrointestinal Medications

   • Metoclopramide 6, 1, 2
   • Prochlorperazine 3
   • Other benzamide derivatives 1

3. Calcium Channel Blockers

   • Flunarizine 1, 2
   • Cinnarizine 1, 2

Moderate-Risk Medications

1. Dopamine-Depleting Agents

   • Reserpine 1
   • Tetrabenazine 1

2. Other Medications

   • Alpha-methyldopa 1
   • Amiodarone 1
   • Lithium 1
   • Valproate (when combined with other agents) 5

Clinical Features of Drug-Induced Parkinsonism

Drug-induced parkinsonism can be clinically indistinguishable from idiopathic Parkinson's disease, but certain features may help differentiate them:

• Bilateral and symmetric symptoms (though about half may present with asymmetric symptoms) 2
• Rapid onset following medication initiation or dose increase 7
• Co-occurrence with other drug-induced movement disorders (particularly tardive dyskinesia) 1
• Symptoms include:
  • Bradykinesia (slowness of movement)
  • Rigidity
  • Tremor (may be less prominent than in idiopathic Parkinson's disease)
  • Postural instability 2

Risk Factors

Certain populations are at higher risk for developing drug-induced parkinsonism:

• Elderly patients (particularly elderly women) 3, 6
• Very young patients 5
• Males (for acute dystonic reactions) 5
• Previous history of tremors 5
• Previous use of antipsychotics 5
• Patients on polypharmacy 5
• Higher doses of antipsychotics 5
• Patients with Parkinson's disease (extremely sensitive to antipsychotic effects) 5

Management Strategies

1. First-line approach:

   • Discontinue the offending medication if clinically feasible 7
   • If antipsychotic cannot be discontinued, consider:
     • Dose reduction 8
     • Switching to an agent with lower risk (quetiapine, clozapine, or pimavanserin) 3, 5, 9

2. Pharmacological management:

   • Anticholinergic medications (e.g., benztropine 1-2 mg daily, maximum 6 mg daily) 5, 8

     • Most effective for younger patients
     • Not recommended for routine prophylaxis 8
     • Contraindicated in elderly patients 8

   • Amantadine

     • Better tolerated in elderly patients 8
     • Similar efficacy to anticholinergics 8

3. For patients with Parkinson's disease requiring antipsychotics:

   • First-line: Pimavanserin 5
   • Second-line: Clozapine 5, 9
   • Third-line: Quetiapine 3, 5

Monitoring and Assessment

• Regular assessment for abnormal movements using standardized scales like the Abnormal Involuntary Movement Scale (AIMS) every 3-6 months 5
• Monitor for development of tardive dyskinesia, which may co-occur with drug-induced parkinsonism 3, 4
• Assess for other extrapyramidal symptoms including:
  • Acute dystonia
  • Akathisia
  • Tardive dyskinesia 3

Important Considerations

• Drug-induced parkinsonism may persist for months or even years after discontinuation of the offending medication 2
• Symptoms may be severe enough to significantly impact quality of life 2
• Dopamine transporter (DAT) imaging may help differentiate drug-induced parkinsonism from idiopathic Parkinson's disease in unclear cases 2
• Beta-blockers (propranolol 10-30 mg two to three times daily) may help manage akathisia, which can co-occur with parkinsonism 5

Drug-induced parkinsonism is often misdiagnosed as idiopathic Parkinson's disease, leading to inappropriate management. Careful medication review and recognition of the temporal relationship between medication initiation and symptom onset are crucial for accurate diagnosis and effective management.