Relationship between clinical features of tricyclic antidepressant poisoning and plasma concentrations in children.

Clinical features and drug plasma concentrations were studied in 13 children admitted to hospital with tricyclic antidepressant poisoning. Patients with plasma concentrations below 500 microgram/l had anticholinergic signs and increased reflexes but did not have convulsions or cardiac arrhythmias. Four patients with plasma concentrations above 1000 microgram/l suffered convulsions, cardiac arrhythmias, or prolonged coma. The diagnosis of poisoning in 2 of these cases was made only by toxicological analysis. Quantitative estimation of tricyclic antidepressants is useful in atypical or severe poisoning both to reach the diagnosis and to give an idea of the likely duration of symptoms.