Incidence of first-time idiopathic seizures in users of tramadol

Study Objective. To assess the risk of idiopathic incident seizures among patients who ever took tramadol. Design. Nested case-control design. Setting. General Practice Research Database from November 1996-August 1998. Patients. Eleven thousand three hundred eighty-three patients. Intervention. Comparison of risks of idiopathic incident seizures during exposed and unexposed times among patients who had ever taken tramadol and other analgesics with 90-day follow-up. Measurements and Main Results. Among the 11,383 subjects we identified 21 cases of idiopathic seizures, 10 of which were categorized as definite cases and 11 categorized as possible cases. Three patients were exposed to tramadol alone in the previous 90 days, 10 to opiates, three to both tramadol and opiates, one to other analgesics, and four to no analgesics. Conclusion. The risk of idiopathic seizures was similarly elevated in each analgesic exposure category compared with nonusers, suggesting that the risk for patients taking tramadol was not increased compared with other analgesics.