Value of initial ECG findings and plasma drug levels in cyclic antidepressant overdose

The role of QRS complex prolongation in predicting severe toxicity in single-xenobiotic overdose

OBJECTIVE

The QRS complex duration is commonly used to prognosticate severity, predict outcomes, and indicate treatment in overdose. However, literature to support this practice is mixed in tricyclic antidepressant overdoses and absent in non-tricyclic antidepressant overdoses. Our objective was to assess the validity of QRS complex duration as a prognostic marker in overdose.

METHODS

This was a secondary analysis of cases reported to the Toxicology Investigators Consortium between January 1, 2010, and December 31, 2022. Cases were assessed to determine the six xenobiotics most associated with QRS complex prolongation. All cases involving these six xenobiotics, regardless of QRS complex duration, constituted the study cohort. Inclusion criteria were cases of patients older than 12 years old with single-xenobiotic exposures. Clinical outcomes evaluated were seizure, ventricular dysrhythmia, metabolic acidosis, and death.

RESULTS

Of 94,939 total cases, diphenhydramine, amitriptyline, bupropion, quetiapine, nortriptyline, and cocaine were most associated with QRS complex prolongation. Inclusion criteria were met by 4,655 cases of exposure to these xenobiotics. QRS complex prolongation was associated with increased odds ratio of seizure in all included xenobiotics, of ventricular dysrhythmia in all included xenobiotics except nortriptyline, and of metabolic acidosis or death in all included xenobiotics except nortriptyline and quetiapine. A normal QRS complex duration had a negative predictive value of greater than or equal to 93.0 percent of developing metabolic acidosis and 98.0 percent of developing a ventricular dysrhythmia or death from the xenobiotics studied.

DISCUSSION

This study demonstrates that patients with QRS complex prolongation from all six xenobiotics studied had an increased prevalence and odds of developing severe outcomes. Furthermore, patients who did not develop QRS complex prolongation were unlikely to develop a ventricular dysrhythmia, metabolic acidosis, or death. These findings were noted in six xenobiotics that mechanistically can cause QRS complex prolongation through sodium channel or gap junction inhibition.

CONCLUSION

Identification of patients at risk for severe outcomes after overdose can be aided by measuring the QRS complex duration. If prospectively validated, these outcomes have implications on risk stratification, disposition level of care, and appropriateness of treatments.

Pharmacological effects and therapeutic potential of natural compounds in neuropsychiatric disorders: An update

Neuropsychiatric diseases are a group of disorders that cause significant morbidity and disability. The symptoms of psychiatric disorders include anxiety, depression, eating disorders, autism spectrum disorders (ASD), attention-deficit/hyperactivity disorder, and conduct disorder. Various medicinal plants are frequently used as therapeutics in traditional medicine in different parts of the world. Nowadays, using medicinal plants as an alternative medication has been considered due to their biological safety. Despite the wide range of medications, many patients are unable to tolerate the side effects and eventually lose their response. By considering the therapeutic advantages of medicinal plants in the case of side effects, patients may prefer to use them instead of chemical drugs. Today, the use of medicinal plants in traditional medicine is diverse and increasing, and these plants are a precious heritage for humanity. Investigation about traditional medicine continues, and several studies have indicated the basic pharmacology and clinical efficacy of herbal medicine. In this article, we discuss five of the most important and common psychiatric illnesses investigated in various studies along with conventional therapies and their pharmacological therapies. For this comprehensive review, data were obtained from electronic databases such as MedLine/PubMed, Science Direct, Web of Science, EMBASE, DynaMed Plus, ScienceDirect, and TRIP database. Preclinical pharmacology studies have confirmed that some bioactive compounds may have beneficial therapeutic effects in some common psychiatric disorders. The mechanisms of action of the analyzed biocompounds are presented in detail. The bioactive compounds analyzed in this review are promising phytochemicals for adjuvant and complementary drug candidates in the pharmacotherapy of neuropsychiatric diseases. Although comparative studies have been carefully reviewed in the preclinical pharmacology field, no clinical studies have been found to confirm the efficacy of herbal medicines compared to FDA-approved medicines for the treatment of mental disorders. Therefore, future clinical studies are needed to accelerate the potential use of natural compounds in the management of these diseases.

Cyclic Antidepressant Poisoning: A Review and Case Report

Although newer cyclic antidepressants have been introduced over the past several years, the tricyclic antidepressants (TCAs) continue to be the leading cause of morbidity from drug overdose in the United States. Overdose features depend on the particular cyclic antidepressant ingested and its pharmacological properties, and can include CNS depression, cardiac arrhythmias, hypotension, seizures, and anticholinergic symptomatology. Life-threatening symptomatology almost always begins within 2 hours, and certainly within 6 hours, after arrival to the emergency department. Plasma TCA levels are unreliable predictors of TCA toxicity and are not recommended. An ECG with a prolonged QRS complex more than 100 msec seems to be the best indicator of serious sequelae with TCAs. Management consists of stabilization of vital signs, gastrointestinal decontamination, intravenous sodium bicarbonate, and supportive care. Agents once thought to be useful for the treatment of cardiac dysrhythmias and seizures such as phenytoin and physostigmine should be avoided. The future of TCA antibody fragments in the treatment of TCA overdose seems promising. Newer and, to some degree, safer antidepressants in overdose have recently been introduced, and they include fluoxetine, trazodone, and sertraline. Amoxapine, bupropion, and maprotiline seem to be as toxic as the TCAs. A significant interaction between cyclic antidepressants and monoamine-oxidase inhibitors exists. Management includes supportive care and basic poison management. Prevention of poisoning seems to be the most logical and effective method of maintaining patient safety. TCAs should be avoided in children younger than 6 years old. All adults with suicidal ideations should receive no more than a 1-week supply (about 1 g) of drug. Finally consideration should be given to using one of the newer, safer antidepressants in all patients with suicidal ideations.

Amitriptyline overdose in emergency department of university hospital: evaluation of 250 patients

OBJECTIVE

The purpose of this study was to evaluate the patients with acute amitriptyline poisoning and investigate predictive factors for the development of life-threatening complications.

METHODS

Demographics, clinical, laboratory, and electrocardiographic (ECG) findings of 250 patients were evaluated retrospectively. Predictive parameters for the development of serious complications were studied.

RESULTS

Median age of patients was 14.6 years, of which, 70% of patients were female and 66% were in pediatric age group. The most common pathological clinical finding and laboratory abnormality were alteration of consciousness and hyponatremia. The rate of convulsive seizure, arrhythmia, and respiratory depression were 17 (6.8%), 16 (6.4%), and 11 (4.4%), respectively. These complications were more seen in pediatric patients than adults (15.8% and 1.2%). The incidence of hyponatremia was more in pediatric patients and severe poisoning groups (38.8 and 53.4%, respectively). The levels of amitriptyline and nortriptyline were significantly higher in the group with complications than the group without complications (p < 0.05). All adult patients were discharged with good prognosis. In pediatric age group, one patient was discharged with severe neurological sequelae and one patient died. QRS duration >100 ms, long corrected QT duration interval, and low Glasgow Coma Score (GCS) at admission were identified as independent risk factors for the development of life-threatening complications (odds ratio: 69.4, 1.9, and 1383, respectively; p < 0.05).

CONCLUSION

Amitriptyline poisoning may be associated with life-threatening complications, especially in pediatric age group and in patients with hyponatremia. Low GCS, presence of hyponatremia, high serum drug levels, and pathological ECG findings on admission may be helpful in predicting the development of complications and poor prognosis.

Antidepressant overdose-induced seizures

Treating patients with psychiatric problems can present numerous challenges for clinicians. The deliberate self-ingestion of antidepressants is one such challenge frequently encountered in hospitals throughout the United States. This review focuses on 1) the classes of antidepressants, their pharmacologic properties, and some of the proposed mechanism(s) for antidepressant overdose-induced seizures; 2) the evidence for seizures caused by antidepressants in overdose; 3) management strategies for patients who have intentionally or unintentionally overdosed on an antidepressant, or who have experienced an antidepressant overdose-induced seizure.

Antidepressant overdose-induced seizures

Antidepressants are the most commonly prescribed class of medications in the United States. The clinician should be mindful of the many antidepressants that can produce seizures following an accidental exposure or an overdose. A broader understanding of the seizure potential of antidepressants, combined with the ability to recognize individuals at risk for a seizure after an overdose, can aid clinicians in determining the need for inpatient monitoring, and help facilitate their treatment decisions.

Diagnosis and treatment of major depressive disorder

Major depressive disorder is a common illness, particularly in patients with medical and neurologic conditions. This article summarizes current data on the epidemiology, diagnosis, and treatment of major depression, with special emphasis on the diagnosis and treatment of depression in medical and neurologic patients. We reviewed the role of pharmacotherapies, psychotherapies, somatic treatments, and alternative remedies and we included practical advice for clinician regarding the timing and sequence of these treatments, the role of standardized depression scales, and the criteria for referrals to specialty consultants.

Tricyclic antidepressant poisoning: an evidence-based consensus guideline for out-of-hospital management

A review of U.S. poison center data for 2004 showed over 12,000 exposures to tricyclic antidepressants (TCAs). A guideline that determines the conditions for emergency department referral and prehospital care could potentially optimize patient outcome, avoid unnecessary emergency department visits, reduce healthcare costs, and reduce life disruption for patients and caregivers. An evidence-based expert consensus process was used to create the guideline. Relevant articles were abstracted by a trained physician researcher. The first draft of the guideline was created by the lead author. The entire panel discussed and refined the guideline before distribution to secondary reviewers for comment. The panel then made changes based on the secondary review comments. The objective of this guideline is to assist poison center personnel in the appropriate prehospital triage and management of patients with suspected ingestions of TCAs by 1) describing the manner in which an ingestion of a TCA might be managed, 2) identifying the key decision elements in managing cases of TCA ingestion, 3) providing clear and practical recommendations that reflect the current state of knowledge, and 4) identifying needs for research. This guideline applies to ingestion of TCAs alone. Co-ingestion of additional substances could require different referral and management recommendations depending on their combined toxicities. This guideline is based on the assessment of current scientific and clinical information. The panel recognizes that specific patient care decisions may be at variance with this guideline and are the prerogative of the patient and the health professionals providing care, considering all the circumstances involved. This guideline does not substitute for clinical judgment. Recommendations are in chronological order of likely clinical use. The grade of recommendation is in parentheses. 1) Patients with suspected self-harm or who are the victims of malicious administration of a TCA should be referred to an emergency department immediately (Grade D). 2) Patients with acute TCA ingestions who are less than 6 years of age and other patients without evidence of self-harm should have further evaluation including standard history taking and determination of the presence of co-ingestants (especially other psychopharmaceutical agents) and underlying exacerbating conditions, such as convulsions or cardiac arrhythmias. Ingestion of a TCA in combination with other drugs might warrant referral to an emergency department. The ingestion of a TCA by a patient with significant underlying cardiovascular or neurological disease should cause referral to an emergency department at a lower dose than for other individuals. Because of the potential severity of TCA poisoning, transportation by EMS, with close monitoring of clinical status and vital signs en route, should be considered (Grade D). 3) Patients who are symptomatic (e.g., weak, drowsy, dizzy, tremulous, palpitations) after a TCA ingestion should be referred to an emergency department (Grade B). 4) Ingestion of either of the following amounts (whichever is lower) would warrant consideration of referral to an emergency department: an amount that exceeds the usual maximum single therapeutic dose or an amount equal to or greater than the lowest reported toxic dose. For all TCAs except desipramine, nortriptyline, trimipramine, and protriptyline, this dose is >5 mg/kg. For despiramine it is >2.5 mg/kg; for nortriptyline it is >2.5 mg/kg; for trimipramine it is >2.5 mg/kg; and for protriptyline it is >1 mg/kg. This recommendation applies to both patients who are naïve to the specific TCA and to patients currently taking cyclic antidepressants who take extra doses, in which case the extra doses should be added to the daily dose taken and then compared to the threshold dose for referral to an emergency department (Grades B/C). 5) Do not induce emesis (Grade D). 6) The risk-to-benefit ratio of prehospital activated charcoal for gastrointestinal decontamination in TCA poisoning is unknown. Prehospital activated charcoal administration, if available, should only be carried out by health professionals and only if no contraindications are present. Do not delay transportation in order to administer activated charcoal (Grades B/D). 7) For unintentional poisonings, asymptomatic patients are unlikely to develop symptoms if the interval between the ingestion and the initial call to a poison center is greater than 6 hours. These patients do not need referral to an emergency department facility (Grade C). 8) Follow-up calls to determine the outcome for a TCA ingestions ideally should be made within 4 hours of the initial call to a poison center and then at appropriate intervals thereafter based on the clinical judgment of the poison center staff (Grade D). 9) An ECG or rhythm strip, if available, should be checked during the prehospital assessment of a TCA overdose patient. A wide-complex arrhythmia with a QRS duration longer than 100 msec is an indicator that the patient should be immediately stabilized, given sodium bicarbonate if there is a protocol for its use, and transported to an emergency department (Grade B). 10) Symptomatic patients with TCA poisoning might require prehospital interventions, such as intravenous fluids, cardiovascular agents, and respiratory support, in accordance with standard ACLS guidelines (Grade D). 11) Administration of sodium bicarbonate might be beneficial for patients with severe or life-threatening TCA toxicity if there is a prehospital protocol for its use (Grades B/D). 12) For TCA-associated convulsions, benzodiazepines are recommended (Grade D). 13) Flumazenil is not recommended for patients with TCA poisoning (Grade D).

Tricyclic antidepressant poisoning : cardiovascular toxicity

Tricyclic antidepressants remain a common cause of fatal drug poisoning as a result of their cardiovascular toxicity manifested by ECG abnormalities, arrhythmias and hypotension. Dosulepin and amitriptyline appear to be particularly toxic in overdose. The principal mechanism of toxicity is cardiac sodium channel blockade, which increases the duration of the cardiac action potential and refractory period and delays atrioventricular conduction. Electrocardiographic changes include prolongation of the PR, QRS and QT intervals, nonspecific ST segment and T wave changes, atrioventricular block, right axis deviation of the terminal 40 ms vector of the QRS complex in the frontal plane (T 40 ms axis) and the Brugada pattern (downsloping ST segment elevation in leads V1-V3 in association with right bundle branch block). Maximal changes in the QRS duration and the T 40 ms axis are usually present within 12 hours of ingestion but may take up to a week to resolve. Sinus tachycardia is the most common arrhythmia due to anticholinergic activity and inhibition of norepinephrine uptake by tricyclic antidepressants but bradyarrhythmias (due to atrioventricular block) and tachyarrhythmias (supraventricular and ventricular) may occur. Torsade de pointes occurs uncommonly. Hypotension results from a combination of reduced myocardial contractility and reduced systemic vascular resistance due to alpha-adrenergic blockade. Life-threatening arrhythmias and death due to tricyclic antidepressant poisoning usually occurs within 24 hours of ingestion. Rapid deterioration is common. Level of consciousness at presentation is the most sensitive clinical predictor of serious complications. Although a QRS duration >100 ms and a rightward T 40 ms axis appear to be better predictors of cardiovascular toxicity than the plasma tricyclic drug concentration, they have at best moderate sensitivity and specificity for predicting complications.

Excess fatality from desipramine and dosage recommendations

Higher case fatality rates (CFR) were previously reported from desipramine than for 3 other tricyclic antidepressants (TCAs): amitriptyline, nortriptyline, and imipramine. The database of the American Association of Poison Control Centers (AAPCC) Toxic Exposure Surveillance System (TESS) for the 20 years 1983-2002 was used to evaluate the CFR of desipramine and the other TCAs. The CFR of desipramine was 2.25-, 2.31-, and 2.62-fold the CFR for amitriptyline, nortriptyline, and imipramine, respectively (P < 0.001). Mechanisms of desipramine toxicity and its dosage recommendations are discussed. Desipramine and nortriptyline have higher distribution volumes and erythrocyte/plasma ratios than their parent compounds imipramine and amitriptyline. This implies lower therapeutic plasma levels and reduced doses for desipramine and nortriptyline compared with their parent compounds. Such adjustments have been done for nortriptyline, but not for desipramine. The authors suggest that the high CFR of desipramine might be reduced by lowering its dose, therapeutic plasma level, and maximal pill content.

A Meta‐Analysis of Prognostic Indicators to Predict Seizures, Arrhythmias or Death After Tricyclic Antidepressant Overdose

OBJECTIVES

To systematically review and summarize studies on the accuracy of ECG and tricyclic antidepressant (TCA) concentration as prognostic indicators of the risk of seizures, ventricular arrhythmia (VA) or death in patients with TCA overdose.

METHODS

Articles were identified with MedLine and Cochrane register of controlled clinical trials searches and review of medical toxicology textbooks. Quality of the included studies was assessed. Pooled estimates of sensitivity, specificity, likelihood ratios and Summary Receiver Operating Characteristics (SROC) curves were generated.

RESULTS

A total of 18 studies were included in the analysis. The pooled sensitivity (Se) and specificity (Sp) of the QRS for predicting seizures were 0.69 [95% CI 0.57-0.78] and 0.69 [95% CI 0.58-0.78] as compared to 0.75 [95% CI 0.61-0.85] and 0.72 [95% CI 0.61-0.81] for the TCA concentration. The Se and Sp of the QRS to predict VA were 0.79 [95% CI 0.58-0.91] and 0.46 [95% CI 0.35-0.59] compared to 0.78 [95% CI 0.56-0.90] and 0.57 [95% CI 0.46-0.67] for the TCA concentration. The Se and Sp of the QRS to predict death were 0.81 [95% CI 0.54-0.94] and 0.62 [95% CI 0.55-0.68] compared to 0.76 [95% CI 0.49-0.91] and 0.60 [95% CI 0.47-0.72] for the TCA concentration. Very few studies evaluated the accuracy of QTc, T 40 ms axis and the R/S ratio.

CONCLUSIONS

Overall, the studies suggested that the ECG and TCA concentration have similar but relatively poor performance for predicting complications, such as seizures, VA or death, associated with TCA overdose.

The toxicity of antidepressant poisoning: is it changing? A comparative study of cyclic and newer serotonin-specific antidepressants

AIM

To compare the clinical features of cyclic antidepressant and newer, non-cyclic, serotonin-specific antidepressant poisoning.

METHODS

Comparitive, descriptive study of all antidepressant overdose patients admitted to a hospital toxicology service from February 1997 to April 2001. Patient data were entered prospectively into a dedicated toxicology database for subsequent analysis.

RESULTS

There were 256 admissions for antidepressant poisoning (17.5% of all poisoning admissions). Cyclic antidepressant poisoning comprised 43% of antidepressant admissions. Statistically significant differences between the two groups included: cyclic antidepressant group had longer median length of stay (23.1 vs 15.9 h, P = 0.0008), greater need for endotracheal intubation (31%vs 4%, OR = 11.5, P < 0.0001) and higher incidence of seizures (7.2%vs 0.7%, OR = 10.4, P = 0.01), faster median pulse rate, longer QRS-interval on admission, and longer intensive care unit stays. However, non-cyclic, serotonin-specific antidepressant poisonings involved larger doses of antidepressants and were more likely to ingest other medications along with these. Serotonin syndrome was only seen in non-cyclic, serotonin-specific poisoning (10.3%, OR = 26.6, P = 0.0002). Patients with serotonin syndrome had a longer median hospital stay (46 vs 16 h, P < 0.0002) compared to other non-cyclic, serotonin-specific patients. There were no deaths during the study period.

CONCLUSIONS

Cyclic antidepressants still comprise a significant proportion of antidepressant poisoning and result in more significant morbidity than non-cyclic, serotonin-specific poisoning. Clinicians should also be aware that non-cyclic, serotonin-specific poisoning may result in the development of serotonin syndrome. This was the most significant toxic effect noted following non-cyclic, serotonin-specific poisoning in this study.

Effects of psychotropic drugs on seizure threshold

Psychotropic drugs, especially antidepressants and antipsychotics, may give rise to some concern in clinical practice because of their known ability to reduce seizure threshold and to provoke epileptic seizures. Although the phenomenon has been described with almost all the available compounds, neither its real magnitude nor the seizurogenic potential of individual drugs have been clearly established so far. In large investigations, seizure incidence rates have been reported to range from approximately 0.1 to approximately 1.5% in patients treated with therapeutic doses of most commonly used antidepressants and antipsychotics (incidence of the first unprovoked seizure in the general population is 0.07 to 0.09%). In patients who have taken an overdose, the seizure risk rises markedly, achieving values of approximately 4 to approximately 30%. This large variability, probably due to methodological differences among studies, makes data confusing and difficult to interpret. Agreement, however, converges on the following: seizures triggered by psychotropic drugs are a dose-dependent adverse effect; maprotiline and clomipramine among antidepressants and chlorpromazine and clozapine among antipsychotics that have a relatively high seizurogenic potential; phenelzine, tranylcypromine, fluoxetine, paroxetine, sertraline, venlafaxine and trazodone among antidepressants and fluphenazine, haloperidol, pimozide and risperidone among antipsychotics that exhibit a relatively low risk. Apart from drug-related factors, seizure precipitation during psychotropic drug medication is greatly influenced by the individual's inherited seizure threshold and, particularly, by the presence of seizurogenic conditions (such as history of epilepsy, brain damage, etc.). Pending identification of compounds with less or no effect on seizure threshold and formulation of definite therapeutic guidelines especially for patients at risk for seizures, the problem may be minimised through careful evaluation of the possible presence of seizurogenic conditions and simplification of the therapeutic scheme (low starting doses/slow dose escalation, maintenance of the minimal effective dose, avoidance of complex drug combinations, etc.). Although there is sufficient evidence that psychotropic drugs may lower seizure threshold, published literature data have also suggested that an appropriate psychotropic therapy may not only improve the mental state in patients with epilepsy, but also exert antiepileptic effects through a specific action. Further scientific research is warranted to clarify all aspects characterising the complex link between seizure threshold and psychotropic drugs.

Plasma alkalinization for tricyclic antidepressant toxicity: a systematic review

OBJECTIVE

To review the evidence that plasma alkalinization improves the outcome in tricyclic antidepressant toxicity.

METHODS

Medline search from 1966 to October 2000 (articles in all languages were included) and examination of bibliographies. Published papers including animal studies, in vitro studies, human case reports, case series and retrospective studies were reviewed.

RESULTS

Our search identified 115 publications, all of which were retrieved. Human studies included eight case reports, four case series, one controlled study and two retrospective chart reviews. No randomized controlled human trials were found. Twelve animal studies were identified that investigated pH manipulation or saline load and their effects on physiological parameters in tricyclic antidepressant toxicity.

CONCLUSIONS

The practice of alkalinization for tricyclic antidepressant toxicity is based on animal studies, case reports and opinion. The mechanism of action appears to be multifaceted and may vary between different tricyclic antidepressants. Significant interspecies variation makes extrapolation from animal studies to humans difficult. Alkalinization therapy appears reasonable in patients with compromising dysrhythmias and shock when supportive interventions have been ineffective; however, the available evidence does not support prophylactic alkalinization in the absence of life-threatening cardiovascular toxicity.

ECG abnormalities in tricyclic antidepressant ingestion

The tricyclic antidepressant (TCA) agents are recognized for their potentially lethal cardiovascular and neurological effects in poisoned patients. The 12-lead electrocardiogram (ECG) has emerged as a popular bedside tool in the evaluation of TCA toxicity. Although the history and physical examination play a key role in the assessment of the patient with potential TCA poisoning, the presence or absence of features of the TCA toxidrome are not sufficient to detect or exclude toxicity from this class of drugs. A variety of ECG findings occur with TCA toxicity. Aside from the sinus tachycardia due principally to anticholinergic effects, TCA-toxic changes seen on the ECG are attributable primarily to the sodium channel blockade caused by these agents. The majority of patients at significant risk for developing cardiac or neurological toxicity will have a QRS complex greater than 0.10 seconds or a rightward shift of the terminal 40 ms of the frontal plane QRS complex vector. The majority of these patients will also display these changes early in their emergency department stay. However, the appearance of these findings, either alone or in combination, does not mean the patient will develop significant cardiac or neurological toxicity. The ECG can neither unequivocally rule in nor rule out impending toxicity; recognizing these limitations, the emergency physician can use this bedside tool in combination with other clinical data during the assessment of the poisoned patient.

Antidepressant Poisoning and Treatment: A Review and Case Illustration

Although newer antidepressants have been introduced over the past several years, the tricyclic antidepressants (TCAs) continue to be a leading cause of morbidity from drug overdose in the United States. Overdose features depend on the particular cyclic antidepressant ingested and its pharmacological properties, and can include CNS depression, cardiac dysrhythmias, hypotension, seizures, and anticholinergic symptoms. Life-threatening events almost always begin within two hours, and certainly within six hours, after arrival to the emergency department. Plasma TCA levels are unreliable predictors of TCA toxicity and are therefore not recommended. An ECG with a prolonged QRS complex more than 100 msec seems to be the best indicator of serious sequelae with TCA overdose. Management consists of stabilization of vital signs, gastrointestinal decontamination, intravenous sodium bicarbonate, and supportive care. Agents once thought to be useful for the treatment of cardiac dysrhythmias and seizures such as phenytoin and physostigmine should be avoided. The future of TCA antibody fragments in the treatment of TCA overdose seems promising. Amoxapine, bupropion, and maprotiline seems to be as toxic as the TCAs. Overdose data is limited for venlafaxine, and mirtazapine, and preclude firm conclusions. A significant interaction between cyclic antidepressants and monoamine-oxidase inhibitors exists. Management includes supportive care and basic poison management. Prevention of poisoning seems to be the most logical and effective method of maintaining patient safety. TCAs should be avoided in children younger than 6 years old. All adults with suicidal ideations should receive no more than a one-week supply (less than 1 g) of drug. Newer and, to some degree, safer antidepressants in overdose have recently been introduced, and they include fluoxetine, sertraline, paroxetine, trazodone, and nefazodone. Finally, consideration should be given to using one of these newer, safer antidepressants in all patients with suicidal ideations.

Cyclic antidepressant toxicity in children and adolescents

We retrospectively evaluated the clinical and laboratory findings of all patients admitted to our facility during a 6.5-year period with a history of cyclic antidepressant ingestion (CAD). Outcome parameters [admission CAD concentration, arterial pH, and corrected QT (QTc) and QRS intervals] used in adult populations to predict morbidity after CAD ingestion were applied to our study population. During the study period, 45 patients (mean +/- SD age of 11.8 +/- 5.6 years) were admitted with CAD ingestion. Conduction delays were present in 17 patients, 9 of whom had QTc intervals greater than 0.43 seconds. Seven patients had generalized seizures; 7 required mechanical ventilation; 14 had Glasgow Coma Scores of 8 or lower on presentation; and one required pharmacologic support for hypotension. In our cohort, the mean admission serum CAD concentration was 461.5 +/- 477.4 ng/mL. Correlations were found between the arterial pH, the QRS interval, the QTc interval, and the admission CAD serum concentration. In an analysis of three subsets of patients (i.e., those with seizures, coma, and respiratory insufficiency), only patients who presented with seizures were found to have a significant prolongation in the QRS and QTc intervals. Pediatric patients who have ingested CADs and present with seizures would appear to be at increased risk for having conduction delays, cardiac dysrhythmias, and, presumably, attendant morbidity and mortality associated with an ingestion.

Comparison of three methods of gut decontamination in tricyclic antidepressant overdose

The purpose of this study was to prospectively compare the effectiveness of three different gut decontamination methods in 51 patients presenting to an emergency department with tricyclic antidepressant overdose. Patients were randomized to three treatments; Group 1 received activated charcoal, Group 2 received saline lavage followed by activated charcoal, and Group 3 received activated charcoal followed by saline lavage followed by activated charcoal. Baseline characteristics of the three groups did not differ, including Glasgow Coma Scores, age, and mean tricyclic antidepressant levels. Average length of stay in admitted patients was 93.3 hours in Group 1, 107.2 hours in Group 2, and 66.7 hours in Group 3. Of those admitted to an ICU, average ICU time was 66.9 hours in Group 1, 54.1 hours in Group 2, and 34.4 hours in Group 3. Average duration of sinus tachycardia was 20.8 hours in Group 1, 30.8 hours in Group 2, and 32.2 hours in Group 3. Of those requiring mechanical ventilation, average ventilator time was 43.4 hours in Group 1, 24.1 hours in Group 2, and 17.8 hours in Group 3. No statistically significant difference could be shown with respect to the clinical endpoints noted. There were no deaths in any of the groups. All three methods of gut decontamination had similar clinical outcomes.

Experimental amitriptyline poisoning: treatment of severe cardiovascular toxicity with cardiopulmonary bypass

STUDY OBJECTIVE

To compare cardiopulmonary bypass (CPB) with more conventional therapy in the treatment of severe amitriptyline poisoning.

DESIGN

Prospective, randomized, controlled, laboratory investigation.

INTERVENTIONS

Profound cardiovascular toxicity was induced in 20 anesthetized Yorkshire swine (72 +/- 8.3 kg) by amitriptyline infusion at 0.5 mg/kg/min. Ventilation was adjusted to keep arterial pH at 7.50 +/- 0.05 and the PCO2 at 35 mm Hg. The swine were randomized in a 1:1 ratio to one of two groups, CPB or control. Both groups received amitriptyline infusion until they experienced near-lethal toxicity, defined as a systolic blood pressure below 30 mm Hg for one minute. The control group was then given supportive treatment, including IV fluids, sodium bicarbonate, vasopressors, and standard pharmacologic (advanced cardiac life support) interventions. Control animals failing to respond to supportive measures after five minutes were given open-chest cardiac massage for 30 minutes or until the return of spontaneous circulation. The CPB group received only mechanical support by CPB for 90 to 120 minutes. No sodium bicarbonate, antiarrhythmics, or cardiotonic agents were provided to the CPB group during this resuscitation.

RESULTS

All 20 animals experienced cardiac conduction delays, dysrhythmias, and progressive hypotension within 30 minutes of receiving IV amitriptyline at 0.5 mg/kg/min. The ten swine receiving CPB as treatment for cardiovascular toxicity were able to completely correct the dysrhythmias, cardiac conduction abnormalities, and hypotension produced by the amitriptyline; however, only one of ten control animals could be resuscitated (P = .0001). Nine of ten swine treated with CPB were easily weaned off bypass without any pharmacologic intervention; however, one required norepinephrine to be weaned. All 11 resuscitated swine were able to be salvaged.

CONCLUSION

CPB improved survival in our swine model of severe amitriptyline poisoning.

Demographic and electrocardiographic factors associated with severe tricyclic antidepressant toxicity

This study was designed to evaluate a historic cohort of pure tricyclic antidepressant overdose patients for factors associated with severe toxicity. Hospitalized tricyclic antidepressant overdose patients were identified by computerized discharge diagnosis (ICD-9 codes). Patients with a serum drug screen positive for tricyclic antidepressants and an emergency department 12-lead electrocardiogram were included in the study. Multiple drug overdoses were excluded. Patients were divided into two groups: minor toxicity (n = 41 and major toxicity (n = 65). Criteria for inclusion in the major toxicity group were the occurrence of seizures, endotracheal intubation, coma, arrhythmias requiring treatment, hypotension, or death. The following were found to be associated with increased likelihood of major toxicity (p less than 0.05): ingestion of amitriptyline (odds ratio (OR) 2.57), age greater than or equal to 30 years (OR 2.56), heart rate greater than or equal to 120 bpm (OR 2.86), serum tricyclic antidepressant level greater than or equal to 800 ng/mL (OR 5.20), terminal 40 ms QRS axis (T40-ms axis) greater than or equal to 135 degrees (OR 2.73), QRS interval greater than or equal to 100 ms (OR 2.74), QRS axis greater than 90 degrees (OR 3.68), and QTc interval greater than 480 ms (OR 3.89). The mean T40-ms axis on the initial ECG was more rightward in the major toxicity group (174 +/- 84 vs 125 +/- 91 degrees, p = 0.006). We conclude that patients with severe tricyclic antidepressant toxicity tended to have a more rightward T40-ms axis than those with minor toxicity and that the presence of the above parameters was associated with an increased likelihood of severe toxicity.