title: Tramadol and seizures: a surveillance study in a managed care population.
abstract: OBJECTIVE
  To investigate the occurrence of tramadol-associated seizures.
  
  
  METHODS
  Retrospective cohort and case-control studies.
  
  
  METHODS
  UnitedHealth Group-affiliated independent practice model health plans, from different regions of the United States, contracting with large networks of physicians.
  
  
  METHODS
  Analysis of administrative data from a large U.S. managed care population.
  
  
  METHODS
  A cohort of 9218 adult tramadol users and 37,232 concurrent nonusers.
  
  
  RESULTS
  Fewer than 1% of users (80) had a presumed incident seizure claim after the first tramadol prescription. Risk of seizure claim was increased 2- to 6-fold among users adjusted for selected comorbidities and concomitant drugs. Risk was highest among those aged 25-54 years, those with more than four tramadol prescriptions, and those with history of alcohol abuse, stroke, or head injury. A case-control study among users was conducted to validate incident seizure outcomes from medical records. Only eight cases were confirmed, and all had cofactors associated with increased seizure risk.
  
  
  CONCLUSIONS
  In a general population, risk of seizure may be associated with long-term therapy with tramadol or the presence of cofactors, or confined to a small sensitive population subset.
authors.affiliation: Department of Pharmacy, University of Washington, Seattle 98195, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Gardner
authors.forename: D
authors.initials: D
authors.lastname: Blough
authors.forename: C R
authors.initials: CR
authors.lastname: Drinkard
authors.forename: D
authors.initials: D
authors.lastname: Shatin
authors.forename: G
authors.initials: G
authors.lastname: Anderson
authors.forename: D
authors.initials: D
authors.lastname: Graham
authors.forename: R
authors.initials: R
authors.lastname: Alderfer
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000701:Analgesics, Opioid / Q000009:adverse effects*; D016022:Case-Control Studies; D015331:Cohort Studies; D004347:Drug Interactions; D005260:Female; D006801:Humans; D007345:Insurance Claim Review; D008137:Longitudinal Studies; D008297:Male; D008329:Managed Care Programs; D008499:Medical Records; D008875:Middle Aged; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012307:Risk Factors; D012640:Seizures / Q000139:chemically induced*; D014147:Tramadol / Q000009:adverse effects*
chemical_list: D000701:Analgesics, Opioid; D014147:Tramadol