Tricyclic antidepressants: plasma levels and clinical findings in overdose

Selective electrochemical detection of antidepressant drug imipramine in blood serum and urine samples using an antimony telluride-graphite nanofiber electrode

A high-performance imipramine (IMPR) sensor has been developed  based on metal chalcogenide-carbon composite materials. The antimony telluride-graphite nanofiber (Sb₂Te₃-GNF, hereafter SBT-GNF) composite was synthesized by the hydrothermal method and confirmed by X-ray powder diffraction (XRD) pattern. The morphology, crystalline lattice, and chemical states were characterized by HRTEM, SAED, and XPS analysis. The characterizations confirmed the formation of an effective composite, SBT-GNF. The SBT-GNF was fabricated as a disposable sensor electrode with a screen-printed carbon electrode (SPCE) and examined for the detection of IMPR by differential pulse voltammetry (DPV). The electroanalytical results of SBT-GNF are compared with the SBT and GNF, and the rational design of effective composite is discussed. SBT-GNF/SPCE showed a good linear range (0.01‑51.8 μM), sensitivity (1.35 ± 0.1 μA μM^-1 cm^-2), and low LOD (4 ± 2 nM). Moreover, the SBT-GNF/SPCE revealed high selectivity and high tolerance limit against potential interfering compounds in blood serum and urine samples. Therefore, this electrochemical sensor can be applicable for the detection of tricyclic antidepressant drug IMPR in clinical and pharmaceutical analysis.

Sonochemical preparation of bismuth oxide nanotiles decorated exfoliated graphite for the electrochemical detection of imipramine

This work described the sonohydrolysis of Bi(NO₃)₃ into Bi₂O₃ and simultaneous sonochemical exfoliation of graphite into graphene sheets in the alkaline environment and its electocatalytic performance towards the detection of anti-depression drug imipramine (IMPR). The ultrasound (37/80 kHz; 60 W) effectively hydrolyzed the Bi(NO₃)₃ into a single crystalline monoclinic phase of Bi₂O₃ nanotiles in the alkaline condition. And also, the sonochemical reaction condition can trigger the lamellar particles on the graphite bulk surface and allowed to exfoliated the graphite (EG) into graphene nanosheets as well. The material characterizations are done by XRD, Raman, FESEM, and HRTEM. It shows the α-Bi₂O₃ nanotiles along with EG nanosheets with high crystallinity and low defects. The (0 0 2) plane in XRD confirms the high crystalline nature of EG. The monoclinic stretching vibrations (90-600 cm^-1) confirms the Raman modes of Bi₂O₃. The prepared Bi₂O₃-EG composites are subjected to the electrochemical determination of IMPR which revealed appreciable analytical performances. The results showed that the Bi₂O₃-EG exhibits better results in the 3 h sonication process. Bi₂O₃-EG-3 exhibited a good linear range (0.02-82.3 µM) and an acceptable limit of detection (6 nM). And also Bi₂O₃-EG-3 exhibits the significant tolerance limit when compared to other potential interfering compounds.

Monitoring of tricyclic antidepressant plasma levels and clinical response: a review of the literature. Part II

Part II of this paper contains some general considerations on tricyclic antidepressant (TCA) monitoring. Long-term assessment of TCA plasma levels is advised by the few existent studies, although each of these focusses on different aspects. Cardiovascular and central nervous system toxicity is reviewed as well as pharmacokinetics and the importance of protein binding. Some consideration is also given to their use in elderly patients. The authors conclude that although available data support its usefulness in many situations, routine measurement of TCA levels is not warranted.

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.

Hemoperfusion in a child with amitriptyline intoxication

Tricyclic antidepressant overdose is one of the most common causes of serious drug poisoning in children and adults. We report a 17-month-old girl with severe amitriptyline intoxication. She was admitted to hospital because of lethargy and seizures. It was estimated that she took approximately 75 mg/kg of amitriptyline 2 h before admission. On examination she was comatose, had ventricular tachycardia and multifocal clonic seizures. Intravenous fluid, per oral activated charcoal, diazepam, lidocaine, and sodium bicarbonate infusion were given. However, there was no response to this therapy, and the patient remained in a deep coma with cardiac arrhythmias and seizures. Hemoperfusion (HP) was performed for 2 h. During this procedure, cardioversion was used six times due to ventricular fibrillation. She had a very good clinical response to HP and no complication was observed. We suggest that HP may be an effective treatment in children with severe amitriptyline intoxication.

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.

Estimating antemortem drug concentrations from postmortem blood samples: the influence of postmortem redistribution

AIMS

To compare blood drug concentrations during life with postmortem drug concentrations measured from a peripheral site and a central site.

METHODS

Coroner's cases from October 1990 to July 1997 were reviewed. Six cases had data on both antemortem and postmortem blood drug concentrations. The postmortem to antemortem ratio was compared with the postmortem central to peripheral ratio, using cardiac blood as a central site and femoral blood as a peripheral site.

RESULTS

Drugs that have a high postmortem central to peripheral ratio; that is, drugs that exhibit considerable postmortem redistribution, also have high postmortem to antemortem ratios.

CONCLUSIONS

A large degree of error can arise from attempting to estimate antemortem drug concentrations and the ingested dose from postmortem measurements. The chosen site and technique for postmortem blood sampling can greatly influence the concentration of drug measured.

Fatality caused by a combined trimipramine-citalopram intoxication

A 53-year-old woman who was diagnosed as suffering from depression was found dead in her bed. The autopsy revealed no morphological changes sufficient to explain death. Toxicological analysis was performed and the drugs trimipramine (2.33 mg/l), citalopram (4.81 mg/l) and zolpidem (0.07 mg/l) were identified in the femoral blood. A combined drug intoxication resulting in synergistic effects to cardiovascular disorders was proposed as the cause of death. An acute overdose and suicide was suggested by calculation of the parent drug to main metabolite ratios in femoral blood and liver tissue. The trimipramine to desmethyltrimipramine ratios were calculated to be 2.06 and 3.18, the citalopram to desmethylcitalopram ratios were 1.96 and 2.02.

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.

The cardiovascular effects of antidepressants

This monograph comprises a review of the cardiovascular effects of the various types of antidepressant drugs in clinical use. The frequency, severity and clinical importance of these effects are placed in perspective. Most antidepressants can cause changes in blood pressure. Both the tricyclic type (TCA) and the monoamine oxidase inhibitors (MAOIs) can produce postural hypotension which may be dose-limiting. In addition, the MAOIs may be associated with severe hypertension when amine-containing foods or medicines are ingested. It is unlikely that therapeutic doses of any available antidepressant drug could impair cardiac contractility. Typical TCAs can cause abnormalities of cardiac conduction and arrhythmias, but this affects less than 5% of patients, mostly to a clinically insignificant extent. Newer compounds such as lofepramine, mianserin, trazodone and viloxazine seem safer in this respect. Reports of an association between therapeutic use of TCAs and sudden death are far from convincing. Overdosage with the MAOIs, lithium and carbamazepine is dangerous but not common; overdose with a TCA is a major source of morbidity and mortality. Lofepramine, mianserin and trazodone are relatively safe in overdose. The use of various antidepressants in patients with hypertension, cardiac failure, angina pectoris, myocardial infarction, or cardiac arrhythmias is discussed and guidelines suggested for the selection and use of antidepressant medication.

Poisoning due to tricyclic antidepressant overdosage. Clinical presentation and treatment

Tricyclic antidepressants are among the commonest causes of both non-fatal and fatal drug poisoning in the world. Their toxicity is due to effects on the brain, the heart, the respiratory system and the parasympathetic nervous system. Symptoms usually appear within 4 hours of an overdose and all but the most seriously poisoned patients recover within 24 hours. The most common clinical features are dry mouth, blurred vision, dilated pupils, sinus tachycardia, pyramidal neurological signs, and drowsiness. In severe poisoning, there may be coma, convulsions, respiratory depression, hypotension and a wide range of electrocardiographic (ECG) abnormalities. The most frequent findings on the ECG are prolongation of the PR and QT intervals; the tracing may resemble bundle branch block or supraventricular or ventricular tachycardias. Treatment of poisoning due to the tricyclic antidepressants is essentially supportive, there being insufficient evidence at present to recommend the use of methods to increase elimination of the drug from the body. Gastric aspiration and lavage should be performed if more than 750 mg of drug have been taken. There must be regular monitoring for hypoxia, acidosis and hypokalaemia and these complications should be corrected enthusiastically. Convulsions should be treated with diazepam or chlormethiazole. Muscular paralysis and artificial ventilation should be employed if anticonvulsants are ineffective. Hypotension should be treated firstly by fluid replacement and then with sympathomimetic agents (dopamine or dobutamine). Antiarrhythmic drugs should only be employed if there is evidence of circulatory failure which fails to respond to correction of hypotension. Sodium bicarbonate infusions should be given to cardiotoxic patients who are acidotic and are worth trying even if the patient is not acidotic. Although physostigmine salicylate will reverse most of the features of tricyclic antidepressant poisoning, its effects are short-lived in serious toxicity and it can produce dangerous side effects; physostigmine should therefore be reserved for those patients who have complications of coma or who have resistant cardiotoxicity or convulsions. Drug screening and quantitative determination of tricyclic antidepressant serum concentrations are useful in a minority of patients who have severe, unusual or prolonged symptoms.

Tricyclic antidepressant poisoning. Management of arrhythmias

Deaths from tricyclic antidepressant (TCA) overdose are usually due to arrhythmias and/or hypotension. Tricyclic antidepressant toxicity is due mainly to the quinidine-like actions of these drugs on cardiac tissues. Slowing of phase 0 depolarisation of the action potential results in slowing of conduction through the His-Purkinje system and myocardium. Slowed impulse conduction is responsible for QRS prolongation and atrioventricular block, and contributes to ventricular arrhythmias and hypotension. Therapies that improve conduction, e.g. hypertonic sodium bicarbonate, are useful in treating these toxic effects. Other mechanisms contributing to arrhythmias include abnormal repolarisation, impaired automaticity, cholinergic blockade and inhibition of neuronal catecholamine uptake. Toxicity may be worsened by acidaemia, hypotension or hyperthermia. Sinus tachycardia is due to the anticholinergic effects of the tricyclic antidepressants as well as blockade of neuronal catecholamine reuptake. Sinus tachycardia is generally well-tolerated and requires no therapy. Sinus tachycardia with QRS prolongation may be difficult to distinguish from ventricular tachycardia. Electrocardiograms obtained using oesophageal or atrial electrodes may be useful in determining the relationship of atrial and ventricular activity. Although QRS prolongation alone is not compromising, it is a marker for patients at highest risk of developing seizures, arrhythmias or hypotension. Ventricular tachycardia (monomorphic) is a consequence of impaired myocardial depolarisation and impulse conduction. Hypertonic sodium bicarbonate may partially correct impaired conduction and be of benefit in treating ventricular tachycardia. Since hypertonic sodium bicarbonate appears to act by increasing the extracellular sodium concentration as well as by increasing extracellular pH, hyperventilation may be less effective. Hypertonic sodium bicarbonate is of particular benefit in patients who are acidotic, since acidosis aggravates cardiac toxicity. However, administration of hypertonic sodium bicarbonate is beneficial even when blood pH is normal. Lignocaine (lidocaine) may be useful in treating ventricular tachycardia but should be administered cautiously to avoid precipitating seizures. Ventricular bradyarrhythmias are due to impaired automaticity or depressed atrioventricular conduction and can be treated by placement of a temporary pacemaker, or with a chronotropic agent, e.g. isoprenaline (isoproterenol), with or without concomitant vasoconstrictors.(ABSTRACT TRUNCATED AT 400 WORDS)

Amitriptyline plasma protein binding: effect of plasma pH and relevance to clinical overdose

Reversing ventricular ectopy with plasma alkalinization following acute tricyclic antidepressant overdose is a recognized mode of therapy. The mechanism responsible for this effect is unclear. Changes in plasma protein binding of free drug, effects of the sodium ion on the myocardium, and alterations of plasma concentrations of alpha-1-acid glycoprotein may all interact to alter toxicity of tricyclics in overdose. An in vitro investigation using equilibrium dialysis was designed to examine the effect of altering plasma pH on percentage of free amitriptyline at clinical overdose plasma concentrations. A 1973 report on this effect lacked adequate controls and was faulty in experimental protocol. The current investigation used plasma concentrations typically present in amitriptyline overdose, a sensitive gas liquid chromatographic assay to detect total and free drug, and adequate control of plasma pH. The results of two separate experiments demonstrated a significant decrease in percentage of free amitriptyline of 20% over a pH range of 7.0-7.4 (P less than 0.05) and 42% over a pH range of 7.4-7.8 (P less than 0.05). The rate of change in slope in both experiments was not significantly different (P less than 0.01) indicating similar effects of pH change on plasma protein binding of amitriptyline within the two groups.

Value of the QRS duration versus the serum drug level in predicting seizures and ventricular arrhythmias after an acute overdose of tricyclic antidepressants

There is a need for a rapid predictor of potential clinical severity to guide therapy in patients with an acute overdose of tricyclic antidepressant drugs. We performed a prospective study of 49 such patients to observe the associations among serum drug levels, maximal limb-lead QRS duration, and the incidence of seizures and ventricular arrhythmias. Patients were divided into two groups on the basis of maximal limb-lead QRS duration. Group A (13 patients) had a duration of less than 0.10 second, and Group B (36 patients) had a QRS duration of 0.10 second or longer. No seizures or ventricular arrhythmias occurred in Group A. In Group B there was a 34 per cent incidence of seizures and a 14 per cent incidence of ventricular arrhythmias. All patients survived. Serum drug levels failed to predict the risk of seizures or ventricular arrhythmias accurately. Seizures occurred at any QRS duration of 0.10 second or longer (P less than 0.05), but ventricular arrhythmias were seen only with a QRS duration of 0.16 second or longer (P less than 0.0005). We conclude that determination of the maximal limb-lead QRS duration predicts the risk of seizures and ventricular arrhythmias in acute overdose with tricyclic antidepressants. Serum drug levels are not of predictive value.

Arterio-venous plasma concentration differences in amitriptyline overdose

The aim of this study was to determine whether femoral arterio-venous plasma concentration differences (AVD) of amitriptyline exist during acute intoxication in man. All patients studied were comatose and were divided into a control group who had two successive blood samples drawn from the same vessel and a study group who had samples drawn from the femoral artery and vein simultaneously. Serial plasma concentrations of amitriptyline were measured by gas liquid chromatography. In each group the differences were assessed by means of the Wilcoxon matched pairs test. In the control group (n = 13) there were no differences (T = 31, n = 12). In the study group (n = 24) the AVD were significantly different (T = 52, n = 23). For amitriptyline, the arterial or venous origin of blood samples for toxicological studies must be stated.

Cardiovascular changes and plasma drug levels after amitriptyline overdose

Electrocardiographic and blood pressure parameters in 17 patients after amitriptyline overdose were reviewed in a retrospective study. Seven patients for whom baseline electrocardiograms (EKGs) were available showed significant increases in heart rate and QRS duration after overdose. Ventricular arrhythmias were observed in only one case, the sole fatality, who demonstrated the highest amitriptyline plus nortriptyline plasma level. Most patients experienced sinus tachycardia (88%) and hypotension (53%). Widened PR and QRS after overdose also were common. For the total group, postoverdose TCAD levels correlated with PR (r = .66, p less than .01) and QRS (r = .55, p less than .05) values, and with lowest observed systolic (r = -.60, p = .01) and diastolic blood pressure (r = .50, p less than .05) but not QTc or heart rate. The difference between the mean TCAD levels of subjects with lowest systolic blood pressure less than 100 mmHg and those with higher readings was significant at the 0.05 level.

Overdosage of antidepressants: clinical and pharmacokinetic aspects

Twenty-nine cases of self-poisoning with antidepressants (amitriptyline, imipramine, clomipramine, maprotiline, doxepine, nortriptyline, opipramol) were examined by frequent observation of CNS effects, heart rate, blood pressure and standard ECG, 24h-ECG-monitoring, measurement of systolic time intervals, EEG recordings and frequent measurement of serum levels of antidepressants and primary metabolites. None of the patients died. Maximum total serum antidepressant level (parent compound + desmethyl metabolite) ranged from 20 to 2200 micrograms/l, with concentrations above 500 micrograms/l in 11 cases. The serum amitriptyline concentration remained high for 3-4 days in some of the severely intoxicated patients and the decay curves were compatible with partly saturated elimination. A degree of unconsciousness and the occurrence of excitation and hallucinations were generally seen in cases with total serum antidepressant levels above 500 micrograms/l. Grand mal seizures occurred more frequently at high antidepressant levels, but could not be predicted from the EEG recordings. Increased heart rate and prolonged QRS- and QTc-intervals were significantly correlated with the total serum antidepressant level. 24 h-ECG-monitoring revealed no serious arrhythmias or instances of heart block. Hypotension was only seen initially in few patients. Systolic time interval measurements showed changes suggesting impaired myocardial performance (elevated PEP/LVET ratio) at intermediate (60-500 micrograms/l) but not high (greater than 500 micrograms/l) total serum antidepressant levels. Measurement of serum concentration in antidepressant intoxication is important for identification of patients with high serum levels and the corresponding risk of developing toxic reactions, and to exclude patients with a low concentration who do not require intensive observation.

Pharmacokinetics of drug overdose

Pharmacokinetics of drugs taken in overdose may differ from those observed following therapeutic doses. Differences are due both to dose-dependent changes and to effects of drugs or pathophysiological consequences of the overdose on kinetics. Dose-dependent changes in rate and extent of absorption, bioavailability (saturation of first-pass metabolism), distribution (saturation of protein binding sites) and metabolism are discussed. Gastrointestinal motility is affected both by specific drug actions, such as delayed gastric emptying by anticholinergic drugs, and by general nervous system depression caused by many drugs. Drug-induced circulatory insufficiency may retard tissue distribution and reduce clearance. Disturbances in blood and urine pH may alter distribution and clearance of weak acids and bases. Drug-induced renal or hepatic failure can significantly decrease clearance. Hypothermia is a common complication of drug overdose and might retard distribution and also reduce clearance. The data concerning pharmacokinetics during overdose are usually incomplete and difficult to interpret. Doses and times of ingestion are uncertain, duration of blood and urine sampling is often inadequate to distinguish absorption from distribution and elimination phases, active metabolites are not measured, protein binding is not determined and clinical features of patients not adequately described. We have, however, reviewed available data for salicylate, paracetamol (acetaminophen), barbiturates, ethchlorvynol, glutethimide, chloral hydrate, tricyclic antidepressants, lithium, phenytoin, ethanol, theophylline, digoxin, amphetamine and phencyclidine.