A systematic review on the use of clozapine in treatment of tardive dyskinesia and tardive dystonia in patients with psychiatric disorders

Rationale: Though clozapine is recommended for treatment of tardive dyskinesia (TD) relating to the use of antipsychotic medications, studies comprehensively investigating the treatment effect of clozapine on TD are still limited. 

Objectives: This review examines the effectiveness of clozapine as an intervention for tardive dyskinesia and dystonia in patients with all psychiatric conditions. Effectiveness of clozapine, duration to exert the effect and dosage used were also analysed.

Methods: A search in the PubMed, PsycINFO and clinicaltrials databases was performed, using the search terms “Clozapine” AND “dyskinesia” OR “dystonia”. Full-text articles that reported the use of clozapine to treat abnormal involuntary movements and were written in English were included. 

Results: A total of 48 studies were identified, of which 13 were clinical trials and 35 were case reports. Significant improvement was seen in 86.7% of patients with schizophrenia spectrum disorders (average dose of clozapine = 355 mg/day) and 93% of patients with other psychiatric disorders (average dose of clozapine = 152.5 mg/day). Patients with other psychiatric diagnoses had faster improvement than the patients with schizophrenia spectrum disorders. Variation in improvements and dosage were also seen in the clinical trials. 

Conclusion: Results suggested an overall effectiveness of clozapine in the treatment of TD for patients with a range of psychiatric conditions. Different response time and clozapine dosage were seen in patients with different psychiatric conditions, suggesting different treatment protocols are required for different conditions. Most of the studies identified are of inadequate qualities, highlighting the need for high quality studies to provide clearer evidence.