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Ask the Mental Health Expert Archives 2001-2004

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TD vs. EPS

Q. Do we know what is the minimum duration a patient has to be on a neuroleptic before developing TD, as opposed to EPS?

A. The short answer is that any movement disorder that develops within a month of beginning a conventional neuroleptic is probably not tardive dyskinesia (TD). By definition, tardive means "after a delay", and this is usually taken to mean after at least a month of treatment. However, one study of older patients with various neuropsychiatric diagnoses found that 16% of patients with less than 3 months of neuroleptic use did develop TD (Sweet et al, Arch Gen Psychiatry 1995;52:478-86). These authors concluded that "...for elderly patients, there may be no absolutely safe duration of neuroleptic treatment."

It must be kept in mind that rates of putative TD are subject to at least two confounding variables: (1) There are drugs that can produce so-called treatment emergent dyskinesias, which may not have the same pathophysiology as TD; e.g., some of the SSRIs can do this (fluoxetine, sertraline, etc.) Unlike most cases of TD, treatment-emergent dyskinesias often remit within a few weeks of drug discontinuation; and (2)dyskinetic movements indistinguishable from TD may occur in patients with a variety of neurological disorders, or in edentulous patients.

In the 19th century, Kraepelin observed some schizophrenic patients with TD-like movements, long before neuroleptics were even developed! Finally, keep in mind that withdrawal dyskinesias-which may be related to TD-can occur within days or weeks of suddenly stopping a conventional neuroleptic. The clinician should always be cautious in labeling a patient's abnormal movements as TD, since this label may be both incorrect and a source of undeserved legal liability.

April 2001

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