Symptoms of Acute

OVERDOSE

• Drowsiness, confusion, disorientation, agitation, coma, death.
• Dryness of mouth, edema of glottis, laryngeal spasms, nasal congestion, blurred vision, vomiting.
• Hyperpyrexia, dilated pupils, muscle rigidity, hyperactive reflexes, areflexia.
• Stupor, and CNS depression or stimulation with convulsions followed by respiratory depression.
• Cardiac abnormalities, including Q.R.S. changes, tachycardia, hypotension, bilateral bundle branch block, ventricular fibrillation, shock, cardiac arrest and congestive heart failure.(See case descriptions below).

Treatment of Acute

OVERDOSE

No specific antidote is known. The drug is not dialyzable.

Treatment should include:

• General supportive measures with emesis and gastric lavage.
• Respiratory assistance is apparently the most effective measure when indicated.
• The administration of barbiturates for control of convulsions alleviates an increase in the cardiac workload, but should be undertaken with caution to avoid potentiation of respiratory depression.
• Intramuscular paraldehyde or diazepam provides anticonvulsant activity with less respiratory depression than do the barbiourates; diazepam seems to be preferred.
• The use of digitalis and/or pliysostigmine may be considered in case of serious cardiovascular abnormalities or cardiac failure.
• Due to several cases of severe cardiotoxicity following Serentil^® (mesoridazine besylate) overdose, continuous ECG monitoring of these patients is recommended.

Two cases are described below:

Marrs-Simon, PA. et al.("Cardiotoxic Manifestations of Mesoridazine Overdose," Ann. Emerg. Med., 17:1074-1078, 1988) describes the management of a 20 year old female who experienced severe cardiotoxicity following an overdose of mesoridazine. The paper also describes similar cases from the published literature.

The serum mesoridazine level in a 115 lb. patient following ingestion of 4.5 to 6.0 grams of Serentil^® (mesoridazine besylate) was 2.5 mcg/mL. She was comatose, hypotensive, convulsing, and had EGG changes. Twenty-four hours later, after hemoperfusion with activated charcoal, the mesoridazine blood levels fell to 1.3 mcg/mL and the patient was normotensive and responsive.

As with other phenothiazines, Serentil^® (mesoridazine besylate) is contraindicated in severe central nervous system depression or comatose states from any cause including drug induced central nervous system depression (see WARNINGS).

Serentil^® (mesoridazine besylate) is contraindicated in individuals who have previously shown hypersensitivity to the drug.

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