The management of tricyclic antidepressant poisoning : the role of gut decontamination, extracorporeal procedures and fab antibody fragments.

Although there have been descriptive, uncontrolled clinical reports of removal of tablet debris by gastric lavage, there have been no clinical studies that have demonstrated that this has any impact on outcome in patients with tricyclic antidepressant (TCA) poisoning. There is also the possibility that lavage may increase drug absorption by pushing tablets into the small intestine. Furthermore, gastric lavage in patients with TCA poisoning may induce hypoxia and a tachycardia potentially increasing the risk of severe complications such as arrhythmias and convulsions. In view of the paucity of evidence that gastric lavage removes a significant amount of drug and the risk of complications associated with the procedure, the routine use of gastric lavage in the management of patients with TCA poisoning is not appropriate. Volunteer studies have shown generally that activated charcoal is more likely to reduce drug absorption if it is administered within 1 hour of drug ingestion. In the one volunteer study that looked at later administration of activated charcoal, there was a 37% decrease in plasma concentration associated with administration of activated charcoal at 2 hours post-ingestion. There have been no clinical studies that enable an estimate of the effect of activated charcoal administration on outcome in the management of patients with TCA poisoning. Volunteer studies have shown that multiple-dose activated charcoal increases the elimination of therapeutic doses of amitriptyline and nortriptyline, but not of doxepin or imipramine; however, these studies cannot be directly extrapolated to the management of patients with TCA poisoning. There have been no well designed controlled studies that have assessed the impact of multiple-dose activated charcoal in the management of patients with TCA poisoning. Because of the large volume of distribution of TCAs, it would not be expected that their elimination would be significantly increased by multiple-dose activated charcoal.Haemoperfusion, haemodialysis and the combination of these procedures do not result in significant removal of TCAs and are not recommended in the management of patients with TCA poisoning.

Overdose profiles of new antipsychotic agents.

Although the more recently introduced antipsychotic drugs are increasing in popularity, the pattern of symptomatology when taken in overdose is not well defined. We monitored all enquiries to the National Poisons Information Service, London (NPIS, London) concerning antipsychotic drugs over a 9-month period in 1997 and report our findings concerning four drugs (olanzapine, clozapine, risperidone and sulpiride). All overdoses involving a single agent were followed up by a letter to the enquirer requesting details and outcome of the case. Although a total of 574 enquiries involving the selected antipsychotic drugs were received, only 45 of these cases involved overdose with a single agent. There were no fatalities or cases of convulsions in the series. Cardiac arrhythmias were only noted with sulpiride. Symptoms were most marked with clozapine, with a majority of patients experiencing agitation, dystonia, central nervous system (CNS) depression and tachycardia. Olanzapine and sulpiride produced a range of different symptoms, while most patients who had taken risperidone were asymptomatic. Monitoring poisons centre enquiries is a useful way of comparing overdose toxicities. We conclude that at least two of the novel antipsychotic agents, olanzapine and risperidone, appear to have a favourable overdose profile, which suggests that they are safer in overdose than the phenothiazines and butyrophenones.