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In the event of overdosage, emergency treatment should be started immediately. Consultation with a poison center should be considered. All patients suspected of having taken an overdose should be hospitalized as soon as possible.
The toxic effects of perphenazine (perphenazine) are typically mild to moderate with death occurring in cases involving a large overdose. Overdosage of perphenazine (perphenazine) primarily involves the extrapyramidal mechanism and produces the same side effects described under ADVERSE REACTIONS, but to a more marked degree. It is usually evidenced by stupor or coma; children may have convulsive seizures. Signs of arousal may not occur for 48 hours. The primary effects of medical concern are cardiac in origin including tachycardia, prolongation of the QRS or QTc intervals, atrioventricular block, torsade de pointes, ventricular dysrhythmia, hypotension or cardiac arrest, which indicate serious poisoning. Deaths by deliberate or accidental overdosage have occurred with this class of drugs.
Treatment is symptomatic and supportive. Induction of emesis is not recommended because of the possibility of a seizure, CNS depression, or dystonic reaction of the head or neck and subsequent aspiration. Gastric lavage (after intubation, if the patient is unconscious) and administration of activated charcoal together with a laxative should be considered. There is no specific antidote.
Standard measures (oxygen, intravenous fluids, corticosteroids) should be used to manage circulatory shock or metabolic acidosis. An open airway and adequate fluid intake should be maintained. Body temperature should be regulated. Hypothermia is expected, but severe hyperthermia may occur and must be treated vigorously. (See CONTRAINDICATIONS.)
An electrocardiogram should be taken and close monitoring of cardiac function instituted if there is any sign of abnormality. Close monitoring of cardiac function is advisable for not less than five days. Vasopressors such as norepinephrine may be used to treat hypotension, but epinephrine should NOT be used.
Since overdosage is often deliberate, patients may attempt suicide by other means during the recovery phase.
Perphenazine (perphenazine) products are contraindicated in comatose or greatly obtunded patients and in patients receiving large doses of central nervous system depressants (barbiturates, alcohol, narcotics, analgesics, or antihistamines); in the presence of existing blood dyscrasias, bone marrow depression, or liver damage; and in patients who have shown hypersensitivity to perphenazine (perphenazine) tablets, their components, or related compounds.
Perphenazine (perphenazine) products are also contraindicated in patients with suspected or established subcortical brain damage, with or without hypothalamic damage, since a hyperthermic reaction with temperatures in excess of 104°F may occur in such patients, sometimes not until 14 to 16 hours after drug administration. Total body ice-packing is recommended for such a reaction; antipyretics may also be useful.
Last reviewed on RxList: 10/21/2008
This monograph has been modified to include the generic and brand name in many instances.
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