Apo-Amitriptyline Overdosage

Symptoms: High doses may cause temporary confusion, disturbed concentration, transient visual hallucinations, agitation, hyperactive reflexes, muscle rigidity, vomiting or hyperpyrexia, in addition to anything listed under Adverse Reactions. Based on amitriptyline's known pharmacologic actions, overdosage may cause drowsiness, hypothermia, tachycardia and other arrhythmic abnormalities such as bundle branch block. ECG evidence of impaired conduction and congestive heart failure. Other manifestations may be dilated pupils, convulsions, severe hypotension, stupor and coma. All patients suspected of having taken an overdose should be admitted to a hospital as soon as possible.
Treatment: Symptomatic and supportive. Empty the stomach as quickly as possible by emesis or gastric lavage. Follow with activated charcoal (50 to 100 g), plus saline cathartic every 4 to 6 hours during the first 24 hours after ingestion as the drug is enterohepatically recycled.
Monitor cardiac function for any signs of dysrhythmia. Asymptomatic patients should be monitored for 6 hours. Patients with ECG changes should be monitored for 24 to 48 hours after ECG has returned to normal.
Maintain ventilation; regulate body temperature.
Maintain fluid and electrolyte balance. Alkalinize blood to pH 7.4 to 7.5 with i.v. sodium bicarbonate. This may prevent tachycardia and other cardiac arrhythmias. Phenytoin may be used for arrhythmias refractory to sodium bicarbonate. Propranolol is effective but its negative inotropic effect may cause hypotension so it should be used with caution. Avoid quinidine and procainamide.
Diazepam i.v. may be given to control seizures.
Forced diuresis, peritoneal dialysis, hemodialysis or charcoal hemoperfusion are not effective in increasing eliminaton.
Since overdosage is often deliberate, patients may attempt suicide by other means during the recovery phase. Deaths by deliberate or accidental overdosage have occured with this class of drugs.
Physostigmine has been useful in treatment of convulsions, cardiac arrhythmias and hallucinations. Not recommended for routine use or to reverse coma. Administer i.v. over 2 minutes to avoid seizures. Adult dose: 2mg; pediatric dose: 0.5 mg. Repeat as required. Have atropine on hand to counteract excessive cholinergic effects