Treatment of severe imipramine poisoning complicated by a negative history of drug ingestion

Seizures associated with poisoning in children: tricyclic antidepressant intoxication

BACKGROUND

The aim of this study was to examine the characteristics of seizure due to poisoning.

METHODS

This was a retrospective analysis, throughout 4 years of hospital admissions for poisoning. Data of patients with seizures due to poisoning were evaluated with respect to the causes, frequencies and complications of seizures.

RESULTS

Among the 1561 admissions due to intoxication during the review period, seizures developed in 26 cases (1.6%). Tricyclic antidepressant overdose (n = 11, 42%) was the leading cause of seizure due to poisoning. Generalized tonic-clonic seizures were observed in 24 patients. Status epilepticus developed in six patients (23%). Mechanical ventilation was applied in 12 (46%) patients. Cardiac complications were observed in 11 (42%) patients with seizures. Two patients who had cardiac arrest due to acepromazine maleate and imipramine intoxication died.

CONCLUSION

One of the causes of seizures in pediatric age group is intoxication. Seizures due to intoxications may cause serious clinical conditions. Intoxications should be thought when a patient is admitted with the diagnosis of afebrile seizure even if there is no history of drug intake.

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.

Alpha-adrenergic receptors mediate imipramine/alarm substance-induced reaction in rats

The mechanism of adverse imipramine-induced reactions (jitteriness, convulsions) was investigated by precipitating such reactions in rats with three injections (IP) of imipramine (5-40 mg/kg) at 24, 5, and 1 h before testing, and comparing their occurrence with comparable treatments using specific noradrenergic and serotonergic reuptake inhibitors [nortriptyline (10 or 30 mg/kg, IP), citalopram (0.5-5.0 mg/kg, IP)]. This initial study indicated that these reactions were mediated by imipramine's noradrenergic effects. Subsequent combinations of imipramine and an alpha 2 agonist (clonidine, 5 mg/kg) and antagonist (yohimbine, 2 mg/kg), and a beta-adrenergic antagonist (propranolol, 2 or 5 mg/kg) (all administered IP 0.5 h after the last injection of imipramine) suggested imipramine's adverse effects were mediated by alpha 2 receptors. The possible involvement of the locus ceruleus in these effects was considered.

Strain differences in convulsions induced by alarm substance

Rats exhibit considerable immobility in the forced swim test when tested in fresh water but almost no immobility when tested in soiled water, that is, water previously swum in by another rat. In this study, we examined the response of different strains of rats to soiled water after treatment with imipramine, which precipitates convulsions in rats tested in soiled water. Male Long-Evans, Sprague-Dawley, Wistar, or Fischer rats were injected with imipramine (20 or 30 mg/kg, IP) and subsequently tested in water soiled by either a Sprague-Dawley or Wistar rat. Significantly more animals convulsed when the soiled water was produced by a Sprague-Dawley rat than a Wistar. More rats also convulsed after receiving the 30-mg/kg dose. Different strains did not react differently to soiled water. This study corroborates and extends previous findings that alarm substances can induce convulsions in imipramine-treated rats and indicates that some strains produce a more potent alarm substance than others.

Alarm substance induces convulsions in imipramine-treated rats

Male rats were injected with imipramine (0-30 mg/kg) and subsequently tested in the forced-swim test in either fresh water or water soiled by other rats, which presumably contains an alarm substance. Imipramine did not affect the behavior of rats in fresh water. More than half the animals given the combination of imipramine (30 mg/kg) and stress from alarm substance had clonic convulsions. Adrenalectomy did not affect this relationship. This is the first study demonstrating the potential of an alarm substance for inducing convulsions.