Symptoms: Dizziness, ataxia, drowsiness, stupor, nausea, vomiting, restlessness, agitation, disorientation, tremor, involuntary movements, opisthotones, abnormal reflexes (slowed or hyperactive): mydriasis, nystagmus, flushing, cyanosis and urinary retention.
Hypotension or hypertension may develop. Coma may ensue. The EEG may show dysthythmias. Laboratory findings in isolated instances of overdosage have included leukocytosis, reduced leukocyte count, glycosuria and acetonuria.
Treatment: There is no known specific antidote to carbamazepine. Experience with accidental carbamazepine overdosage is limited. Since carbamazepine is chemically related to tricyclic antidepressant imipramine, reference to treatment of imipramine overdosage is relevant. Induce emesis and perform gastric lavage. Observe vital signs and administer symptomatic treatment as required. Hyperirritability may be controlled by the administration of parenteral barbiturates; however, barbiturates should not be used if drugs that inhibit MAO have also been taken by the patient, either overdosage or in recent therapy (within two weeks).
Barbiturates may also induce respiratory depression, particularly in children. Have equipment available for artificial ventilation and resuscitation when barbiturates are employed. Paraldehyde may be used to counteract muscular hypertonus without producing respiratory depression. Treat shock (circulatory collapse) with supportive measures including IV fluid, oxygen and corticosteroids. Monitor the EGG to detect any cardiac arrhythmias or conduction defects, particularly in children.