Seizure in venlafaxine overdose: a 10-year retrospective review of the California poison control system

Background: The optimal observation time period with respect to seizures after venlafaxine overdose is unclear. We conducted a 10-year retrospective review of calls to the California Poison Control System to describe the time of onset of seizures in adult and pediatric overdose of venlafaxine. Methods: Inclusion criteria included adult and pediatric patients with exposure to venlafaxine, who were admitted to a health care facility and who had at least one seizure. We did not exclude cases in which co-ingestions of other drugs were reported. Data extraction of a priori defined variables was recorded. Descriptive statistics were used to characterize the cohort of patients, including means, medians, and interquartile ranges. Results: The total number of cases included in the data analysis was 123 (12.9% of all venlafaxine ingestions). The longest time to last seizure was 24 h. Twenty-five percent of participants had a seizure from hour 7 to 24 h. This did not differ significantly between IR and XR formulations. Conclusions: Optimal observation time with respect to seizures after overdose of immediate-release formulation of venlafaxine is 18 h (24 h if ingested with other medications), and 21 h for patients who are poisoned with the sustained-release formulation.