Epidemiology of fatal tricyclic antidepressant ingestion: implications for management

Late death in tricyclic antidepressant overdose revisited

We report a late death following the ingestion of amitriptyline. A 46-year-old woman presented to the emergency department with coma, hypotension, tachycardia, and a prolonged QRS interval after the ingestion of a large quantity of Elavil. She was managed with aggressive supportive care, multiple doses of oral charcoal, and charcoal hemoperfusion. The patient's ECG and hemodynamic status returned to normal within 24 hours. Despite an apparent total recovery, she suddenly sustained a cardiorespiratory arrest and died 33 hours after ECG normalization (at 57 hours after admission). This case brings into question the feasibility of ceasing ECG monitoring in tricyclic antidepressant overdoses once the ECG has stabilized, especially in patients with a history of chronic usage. A possible explanation for late sequelae is the myocardial cell binding and depressant effect of preexisting therapeutic TCA medication.

Tricyclic antidepressant overdose: emergency department findings as predictors of clinical course

There is controversy regarding the appropriate utilization of health care resources in the management of tricyclic antidepressant overdosage. Antidepressant overdose patients presenting to the emergency department (ED) are routinely admitted to intensive care units, but only a small proportion develop cardiac arrhythmias or other complications requiring such an environment. The authors reviewed the findings in 165 patients presenting to an ED with antidepressant overdose. They found that major manifestations of toxicity on ED evaluation (altered mental status, seizures, arrhythmias, and conduction defects) were commonly associated with a complicated hospital course. Patients with the isolated findings of sinus tachycardia or QTc prolongation had no complications. No patient experienced a serious toxic event without major evidence of toxicity on ED evaluation and continued evidence of toxicity during the hospital course. These data support the concept that proper ED evaluation can identify a large body of patients with trivial ingestions who may not require hospital observation.

Management of poisoning associated with "newer" antidepressant agents

Overdose of tricyclic antidepressants remains one of the most difficult poisonings to manage optimally in the emergency department, primarily due to the extremely rapid onset of life-threatening symptomatology. The continued high incidence of such overdoses has ensured that morbidity and mortality rates also remain unacceptably high. The development of the "second-generation antidepressants," with apparently different pharmacology and toxicity after overdose, has been an attempt to address this serious medical problem. This report reviews the published literature on the overdose toxicology of the newer cyclic antidepressants currently available in the United States--amoxapine, maprotiline, and trazodone. Nomifensine, released by the FDA in 1984, recently has been voluntarily withdrawn from the world market. Bupropion, released in 1985, also has been voluntarily withdrawn by the manufacturer three months after its release.

Phenytoin: does it reverse tricyclic-antidepressant-induced cardiac conduction abnormalities?

Case reports have appeared describing a beneficial effect of phenytoin in reversing cardiac conduction abnormalities induced by tricyclic antidepressant (TCA) overdose. Controlled studies have not been published. The following questions were addressed using intravenous amitriptyline and phenytoin in a rabbit model: Can prophylaxis with phenytoin before amitriptyline poisoning forestall the onset of cardiac abnormalities? Would such prophylactic phenytoin administration allow a higher dose of amitriptyline before death occurs? Would phenytoin reverse the cardiotoxic effects of amitriptyline once in progress? Animals were used in repeated trials with one-week "washout" intervals and served as their own controls in all but the final trial. Prophylactic phenytoin did not change the potency of amitriptyline in inducing abnormal cardiac performance, nor did it allow the animals to be titrated to a higher dose of amitriptyline before death occurred. In 12 animals, phenytoin "rescue" at the point of a widened QRS or arrhythmia was attempted. Two showed improvement; the remainder did not. Because this portion of the experiment was neither blinded nor controlled, nor were respirations or blood pressure monitored, these results must be viewed cautiously. Although our results suggest that prophylactic phenytoin is not useful, its role in therapy of occasional cases requires further investigation.

Membrane stabilising activity: a major cause of fatal poisoning

Many of the agents held responsible for fatal poisoning in England and Wales--particularly dextropropoxyphene, tricyclic antidepressants, beta-adrenergic antagonists, and chlorpromazine--possess membrane stabilising activity (MSA). This pharmacological property, although regarded as being of little importance in therapeutic use, may be responsible for death in more than 30% of fatal poisonings. Awareness of this possibility may lead to greater care in the prescribing of drugs with this property, to the development of safer alternatives, and to more rational therapy of the poisoned patient.

Tricyclic antidepressant overdose

Overdose of a tricyclic antidepressant is a serious and all-too-frequent occurrence. The diagnosis must be considered in known or suspected overdoses, and signs such as a dry axilla, tachycardia, and wide QRS must be specifically sought. Management depends upon support of vital functions and a thorough understanding of the pharmacology of the drug. Emptying the gastrointestinal tract with ipecac or lavage and hastening elimination with activated charcoal and a cathartic are extremely important measures. Cardiac arrhythmias generally respond to sodium bicarbonate, and seizures respond to intravenous diazepam. Neither physostigmine nor dialysis are considered to be treatments of choice. As in other overdoses, counseling to prevent ingestions is more than worth "a pound of the cure."

Improvement of cardiac conduction after hyperventilation in tricyclic antidepressant overdose

Three patients wtih severe cardiotoxicity secondary to tricyclic antidepressant (TCA) overdosage were treated with induced mechanical hyperventilation. All three demonstrated marked QRS narrowing, reflecting improved intracardiac conduction, after hyperventilation therapy. Such therapy may help to prevent or abolish ventricular dysrhythmias, often a feature of life-threatening TCA overdoses.