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.

The National Poisons Unit, London, carried out a pilot survey to investigate the frequency and severity of adverse effects/toxicity from exposure to traditional medicines and food supplements reported to the Unit. Enquiries related to suspected poisoning events were reviewed retrospectively from January 1983 to March 1989, and prospectively in 1991. Further information about cases identified by the prospective review was obtained, when appropriate, by follow-up questionnaire, clinical consultation by a consultant toxicologist, toxicological analyses of samples from patients and from products, and botanical identification of dried plant material. In total, 5536 enquiries were identified. Symptoms were reported in 657 (12%) of these. There was a large number of reports of accidental ingestion of vitamin preparations by children under 5 years. Appropriate assessment was possible in only relatively few cases, due to insufficient documentation, and poor labelling of certain products. A probable link between exposure and adverse effects was identified in 42 cases, and was highly probable in two. Heavy metal poisoning resulting from use of contaminated traditional remedies was confirmed in 5 cases. There was evidence that some patients took excessive doses of food supplements, without realising that this might result in toxic effects. The results of this pilot study suggest that there is a need for further surveillance to provide an appropriate risk assessment of food supplements and herbal remedies, improved quality control and labelling of these products, and increased awareness of their potential hazard.

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.

Most exposures are of little consequence. However, there are clear epidemiological differences between sex and age groups. These findings will help inform prevention strategies.

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