The toxicity of antidepressant poisoning: is it changing? A comparative study of cyclic and newer serotonin-specific antidepressants.

AIM: To compare the clinical features of cyclic antidepressant and newer, non-cyclic, serotonin-specific antidepressant poisoning. METHODS: Comparitive, descriptive study of all antidepressant overdose patients admitted to a hospital toxicology service from February 1997 to April 2001. Patient data were entered prospectively into a dedicated toxicology database for subsequent analysis. RESULTS: There were 256 admissions for antidepressant poisoning (17.5% of all poisoning admissions). Cyclic antidepressant poisoning comprised 43% of antidepressant admissions. Statistically significant differences between the two groups included: cyclic antidepressant group had longer median length of stay (23.1 vs 15.9 h, P = 0.0008), greater need for endotracheal intubation (31%vs 4%, OR = 11.5, P < 0.0001) and higher incidence of seizures (7.2%vs 0.7%, OR = 10.4, P = 0.01), faster median pulse rate, longer QRS-interval on admission, and longer intensive care unit stays. However, non-cyclic, serotonin-specific antidepressant poisonings involved larger doses of antidepressants and were more likely to ingest other medications along with these. Serotonin syndrome was only seen in non-cyclic, serotonin-specific poisoning (10.3%, OR = 26.6, P = 0.0002). Patients with serotonin syndrome had a longer median hospital stay (46 vs 16 h, P < 0.0002) compared to other non-cyclic, serotonin-specific patients. There were no deaths during the study period. CONCLUSIONS: Cyclic antidepressants still comprise a significant proportion of antidepressant poisoning and result in more significant morbidity than non-cyclic, serotonin-specific poisoning. Clinicians should also be aware that non-cyclic, serotonin-specific poisoning may result in the development of serotonin syndrome. This was the most significant toxic effect noted following non-cyclic, serotonin-specific poisoning in this study.