Clinical aspects of tricyclic antidepressant poisoning

Self-poisoning with antidepressant drugs was studied retrospectively in 225 patients admitted to an intensive care unit. Amitriptyline accounted for the overwhelming majority of cases (70%); 106 patients (47%) had taken two or more drugs, in 81 patients (36%) ethanol was found in the blood. Four patients (2%) died. On admission, 111 patients (49%) were unconscious (grade III). A further 30 patients (13%) were in grade IV coma, and of these 27 had taken amitriptyline. Twenty-four hours after admission, 22 patients (10%) remained in coma. Thirty-six patients (16%) required assisted ventilation. Nineteen patients (8%) had convulsions and 6 (3%) aspired stomach contents. Sixty-one patients (27%) had a widened QRS interval exceeding 100 msec, 18 (30%) of them required assisted ventilation, 21 (34%) were in stage IV coma and 15 (25%) had convulsions. This relationship between a widened QRS interval and the severity of intoxication should be considered in the initial assessment of patients with tricyclic antidepressant poisoning.

Severe amitriptyline overdose: relationship between toxicokinetics and toxicodynamics

The clinical features and toxicokinetics of amitriptyline were studied in nine patients with severe amitriptyline poisoning. Amitriptyline and amitriptyline metabolites were studied in plasma, red blood cells, and cerebral spinal fluid. Eight patients were intubated and six required assisted ventilation. Two patients had ventricular arrhythmias, three patients convulsions and two were hypotensive. All complications developed within four hours of admission. Early in the course of the intoxication the QRS duration correlated with plasma, unbound and red blood cell nortriptyline concentration. The QRS duration also correlated with unbound but not the plasma amitriptyline concentration. The level of consciousness correlated with the plasma and unbound amitriptyline both in alpha and beta phase and with red blood cell amitriptyline in alpha phase. There was no correlation between nortriptyline concentration and level of consciousness. No correlation between coma grade or QRS duration and cerebral spinal fluid concentration of amitriptyline was found. There was no correlation between any hydroxymetabolite in blood or cerebral spinal fluid and QRS duration or coma grade. The beta half-life for amitriptyline was shorter for two patients with high concentrations of hydroxymetabolites. Although intubated, neither patient required assisted ventilation or developed complications. Because of the wide range of concentrations of amitriptyline and amitriptyline metabolites observed between individuals, it is not possible to predict outcome based on a single tricyclic antidepressant concentration.

Amitriptyline and amitriptyline metabolites in blood and cerebrospinal fluid following human overdose

The toxicokinetics of amitriptyline were studied in nine patients admitted to hospital in Matthew-Lawson Coma Scale grade III-IV after an estimated ingestion of 1-5 g amitriptyline. Gastric lavage was performed and 50 g activated charcoal were given orally. Venous blood samples were taken on admission and at 1, 2, 4, 8, and 24 h, and in some patients at 36 and 48 h after admission. Arterial blood samples were taken at 1, 4, 8, and 24 h after admission. Lumbar punctures were performed 1 h after admission in 8 patients and again 4 h later in 5 patients. A urine sample was screened for other drugs. The bound and unbound fraction of amitriptyline and its metabolites nortriptyline, E and Z forms of 10-OH-amitriptyline and nortriptyline were analyzed in plasma, whole blood, red blood cells, and cerebrospinal fluid using an HPLC technique. The T1/2 alpha and T1/2 beta for amitriptyline were 1.5 - 3.1 and 15 - 43 h respectively. The rate of elimination of amitriptyline was not dose-dependent. The arteriovenous differences in the total amitriptyline+nortriptyline concentration were maximal in patients admitted soon after intake of drugs. Amitriptyline concentrations in cerebrospinal fluid were quantitatively similar to the unbound amitriptyline concentration in blood. The highest cerebrospinal fluid amitriptyline concentration was 506 nmol/L. There were large individual differences in plasma, blood and cerebrospinal fluid concentrations between different individuals. Repeated quantitative analysis of amitriptyline and its metabolites is unlikely to contribute to the clinical management of most patients with amitriptyline overdose.

Predicting severity of tricyclic antidepressant overdose

The measurement of plasma concentration, a prolonged QRS interval, and level of consciousness have all been recommended as useful indicators of toxicity following tricyclic antidepressant overdose. The aims of this study were firstly, to determine the relative prognostic value of each of these indicators and secondly, to assess when a patient can be discharged safely from the intensive care unit. Data were evaluated on 67 patients with tricyclic antidepressant overdose from four centers. Plasma tricyclic antidepressant concentrations were measured, coma grade was evaluated using the Matthew-Lawson Coma Scale and a ECG was obtained from 23 patients on admission. Complications such as convulsions, hypotension, arrhythmias, and need for intubation and ventilation were recorded. Thirty patients developed complications and no patient died. Coma grade was the best predictor of outcome. The development of serious complications is unlikely in patients whose level of consciousness is grade II or less and who are admitted to hospital more than 6 h after overdose. Plasma tricyclic antidepressant concentration was of no additional value in predicting toxic complications or deciding when the patient could leave the intensive care unit. Our study suggests that an alert and orientated patient with a QRS duration less than 100 ms is the best indicator for safe transfer to a medical or psychiatric ward.

TCA poisoning treated in the intensive care unit

Intoxication with tricyclic antidepressants (TCA) is a common cause of admission to an intensive care unit and a major cause of death due to drug overdose. It is difficult to identify at an early stage those patients for whom toxic events are likely. There is a poor correlation between the plasma concentration of TCAs and the risk of developing toxic symptoms. A better predictor of complications following tricyclic overdose is the level of consciousness on admission to hospital. It has been claimed that "newer" antidepressant agents are less toxic then the classic antidepressants when taken in overdoses. In Sweden, two of these "newer" antidepressants, maprotiline and lofepramine, have been marketed. Of these, only lofepramine is less toxic than the classic TCAs. Maprotiline has the same cardiotoxicity as the TCAs, convulsions are seen more often and a longer plasma half-life leads to longer time spent on a ventilator and longer time in an ICU when it is taken in overdose.

Terbutaline concentrations in self-poisoning: a case report

A young female patient was admitted twice within two months, each time after an overdose of 500 mg terbutaline. Clinical features included nausea, tachycardia, tremor, hyperglycemia and hypokalemia. Although plasma concentrations of terbutaline were at least 50 times the normal therapeutic level, after potassium substitution the outcome was uneventful.

Does alcohol absorb to activated charcoal?

Activated charcoal seldom is used in pure-alcohol poisoning since it is absorbed rapidly from the gut. Furthermore in early reports activated charcoal was found to adsorb alcohol poorly. However, in 1981 North et al. [North, D. S., Thompson, J. D. & Peterson, C. D. (1981). Am. J. Hosp. Pharm., 38, 864-866] demonstrated in dogs that charcoal given at the same time as alcohol can reduce the blood alcohol concentration significantly. To study whether charcoal is of value in a clinical situation, a randomized cross-over study in two phases was conducted. Each person drank 88 g of alcohol and 30 min after either 20 g of activated charcoal was taken or the same volume of water was drunk. There were no significant differences in plasma alcohol concentrations with or without charcoal.