Dystonia Secondary to Use of Antipsychotic Agents

Following the introduction of first-generation antipsychotics (FGAs) in the early 1950s, there was a radical change in the therapeutic regimens for schizophrenia. However, it soon became apparent that these antipsychotic agents produced serious side effects including distressing and often debilitating movement disorders known as extrapyramidal symptoms (EPS). To prevent EPS, second-generation antipsychotics (SGAs) were developed and introduced, including risperidone in 1996, quetiapine, perospirone, and olanzapine in 2001, aripiprazole in 2006, and blonanserin in 2008. Clozapine was approved in 2010 in Japan with strict regulation of its use. These newer medications differ from FGAs, primarily on the basis of their reduced risk of inducing EPS. EPS lie at the interface of neurology and psychiatry and have generated a vast literature in both disciplines. EPS can be categorized as acute (dystonia, akathisia and parkinsonism) and tardive (tardive dyskinesia, tardive akathisia and tardive dystonia). Acute EPS has often been reported as an early sign of predisposition to tardive dyskinesia. Acute and tardive EPS may also adversely influence a patient’s motor and mental performance and reduce compliance to treatment. Poor compliance leads to high relapse rates, with both ethical and economic consequences. Acute dystonic reaction is a common side effect of antipsychotics, but can be caused by any agents that block dopamine receptors, such as the antidepressant amoxapine and anti-emetic drugs such as metoclopramide.