OVERDOSAGE
(See also.)
ADVERSE REACTIONS
Symptoms
Primarily symptoms of central nervous system depression to the point of somnolence or coma. Hypotension and extrapyramidal symptoms.
Other possible manifestations include agitation and restlessness, convulsions, fever, autonomic reactions such as dry mouth and ileus, EKG changes and cardiac arrhythmias.
Treatment
It is important to determine other medications taken by the patient since multiple drug therapy is common in overdosage situations. Treatment is essentially symptomatic and supportive. Early gastric lavage is helpful. Keep patient under observation and maintain an open airway, since involvement of the extrapyramidal mechanism may produce dysphagia and respiratory difficulty in severe overdosage. Extrapyramidal symptoms may be treated with anti-parkinsonism drugs, barbiturates or diphenhydramine. See prescribing information for these products. Care should be taken to avoid increasing respiratory depression.
Do not attempt to induce emesis because a dystonic reaction of the head or neck may develop that could result in aspiration of vomitus.
If administration of a stimulant is desirable, amphetamine, dextroamphetamine or caffeine with sodium benzoate is recommended. Stimulants that may cause convulsions (e.g., picrotoxin or pentylenetetrazol) should be avoided.
If hypotension occurs, the standard measures for managing circulatory shock should be initiated. If it is desirable to administer a vasoconstrictor, norepinephrine and phenylephrine are most suitable. 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. Limited experience indicates that phenothiazines are dialyzable.
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