title: Risk of non-fatal venous thromboembolism in women using oral contraceptives containing drospirenone compared with women using oral contraceptives containing levonorgestrel: case-control study using United States claims data.
abstract: OBJECTIVE
  To compare the risk of non-fatal venous thromboembolism in women receiving oral contraceptives containing drospirenone with that in women receiving oral contraceptives containing levonorgestrel.
  
  
  METHODS
  Nested case-control and cohort study.
  
  
  METHODS
  The study was based on information from PharMetrics, a United States based company that collects information on claims paid by managed care plans.
  
  
  METHODS
  The study encompassed all women aged 15 to 44 years who received an oral contraceptive containing either drospirenone or levonorgestrel after 1 January 2002. Cases were women with current use of a study oral contraceptive and a diagnosis of venous thromboembolism in the absence of identifiable clinical risk factors (idiopathic venous thromboembolism). Up to four controls were matched to each case by age and calendar time.
  
  
  METHODS
  Odds ratios comparing the risk of non-fatal venous thromboembolism in users of the two contraceptives; incidence rates and rate ratios of non-fatal venous thromboembolism for users of each of the study contraceptives.
  
  
  RESULTS
  186 newly diagnosed, idiopathic cases of venous thromboembolism were identified in the study population and matched with 681 controls. In the case-control analysis, the conditional odds ratio for venous thromboembolism comparing use of oral contraceptives containing drospirenone with use of those containing levonorgestrel was 2.3 (95% confidence interval 1.6 to 3.2). The incidence rates for venous thromboembolism in the study population were 30.8 (95% confidence interval 25.6 to 36.8) per 100,000 woman years among users of oral contraceptives containing drospirenone and 12.5 (9.61 to 15.9) per 100,000 woman years among users of oral contraceptives containing levonorgestrel. The age adjusted incidence rate ratio for venous thromboembolism for current use of oral contraceptives containing drospirenone compared with those containing levonorgestrel was 2.8 (2.1 to 3.8).
  
  
  CONCLUSIONS
  The risk of non-fatal venous thromboembolism among users of oral contraceptives containing drospirenone seems to be around twice that of users of oral contraceptives containing levonorgestrel, after the effects of potential confounders and prescribing biases have been taken into account.
authors.affiliation: Boston Collaborative Drug Surveillance Program, Boston University School of Medicine, Lexington, MA 02421, USA. sjick@bu.edu
authors.forename: Susan S
authors.initials: SS
authors.lastname: Jick
authors.forename: Rohini K
authors.initials: RK
authors.lastname: Hernandez
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000736:Androstenes / Q000009:adverse effects*; D016022:Case-Control Studies; D003277:Contraceptives, Oral, Combined / Q000009:adverse effects*; D005260:Female; D006801:Humans; D016912:Levonorgestrel / Q000009:adverse effects*; D012307:Risk Factors; D014481:United States; D054556:Venous Thromboembolism / Q000139:chemically induced*; D055815:Young Adult
chemical_list: D000736:Androstenes; D003277:Contraceptives, Oral, Combined; D016912:Levonorgestrel; C035144:drospirenone