These symptoms usually can be controlled by an antiparkinsonian agent. Tardive dyskinesia can occur with long-term therapy, and the risk of developing this effect is increased in geriatric patients. It occurs rarely unless thiethylperazine use is prolonged for weeks or months. Symptoms of tardive dyskinesia are persistent and include rhythmic involuntary movements of the tongue, face, mouth, or jaw, which can be accompanied by involuntary movements of the extremities. Other CNS effects include drowsiness, dizziness, and seizures.
Drowsiness is common and disappears with time.
Dizziness may be due to a central effect or to orthostatic hypotension. Seizures occur because of a lower threshold. Seizures are not common but should be considered, especially when using thiethylperazine in patients with a seizure history. Anticholinergic effects and adrenergic blockade are seen with thiethylperazine. Patients may complain of xerostomia, blurred vision, constipation, and urinary retention.