Lesser degrees of overdosage may case muscular twitching, drowsiness or dizziness. Symptoms of gross overdosage may include central nervous system depression, weakness, tremor, torticollis and dystonia. Agitation and restlessness may occur. Salivation, dysphagia, or disturbances of gait may also be present. Treatment is essentially symptomatic and supportive.
Gastric lavage is helpful if performed early.
Do not attempt to induce emesis because a dystonic reaction of the head or neck may develop that could result in aspiration of vomitus. The patient should be kept under careful observation and particular attention should be directed to maintaining an open airway, since involvement of the extrapyramidal mechanism may produce dysphagia and respiratory difficulty in severe cases of overdosage. Other pressor agents, including epinephrine, are not recommended because phenothiazine derivatives may reverse the usual elevating action of these agents and cause a further lowering of blood pressure. Extrapyramidal symptoms may be treated with antiparkinsonian drugs or diphenhydramine. Peritoneal dialysis and hemodialysis have been found ineffective in the treatment of acute phenothiazine poisoning.