The risk of seizures associated with tramadol.

We conducted a study of the risk of idiopathic incident seizures among users of tramadol derived from data present in the General Practice Research Database based in the United Kingdom for 1994-1996. We used a nested case-control study design, comparing risks of idiopathic incident seizures during exposed and unexposed times among patients who had ever taken tramadol using a 90-day follow-up. Among the 10,916 subjects, we identified 17 cases of idiopathic seizures, 11 of which were definite and 6 possible. None of the patients was exposed to tramadol alone in the prior 90 days. Eight patients were exposed to opiates, five to both tramadol and opiates, three to other analgesics, and one to no analgesics. We found no increased risk of idiopathic incident seizures associated with exposure to tramadol alone. Thus seizures seem rarely attributable to the agent.