Risk of thromboembolism in women taking ethinylestradiol/drospirenone and other oral contraceptives.
OBJECTIVE
The oral contraceptive ethinylestradiol 0.03 mg/drospirenone 3 mg contains a progestin component that differs from other oral contraceptives. Case reports and prescription event monitoring suggested that ethinylestradiol/drospirenone might be associated with an elevated risk of thromboembolism. We sought to estimate the association between ethinylestradiol/drospirenone and risk of thromboembolism relative to the association among other oral contraceptives.


METHODS
We identified ethinylestradiol/drospirenone initiators and a twofold larger group of other oral contraceptive initiators between June 2001 and June 2004 within a U.S. health insurer database. The comparison group was selected to have demographic and health care characteristics preceding oral contraceptive initiation that were similar to ethinylestradiol/drospirenone initiators. Thromboembolism during the follow-up of the cohorts was identified through claims for medical services, and only medical record-confirmed cases were included in analyses. The primary (as-matched) analysis used proportional hazards regression, whereas a secondary (as-treated) analysis accounted for changes in oral contraceptives during follow-up using Poisson regression.


RESULTS
The 22,429 ethinylestradiol/drospirenone initiators and 44,858 other oral contraceptive initiators were followed for an average of 7.6 months, and there were 18 cases of thromboembolism in ethinylestradiol/drospirenone initiators and 39 in the comparators (rate ratio 0.9, 95% confidence interval 0.5-1.6). More than 9,000 women would need to be prescribed oral contraceptives to observe a difference of one case of thromboembolism. Results of the as-treated analysis were similar to those of the as-matched analysis.


CONCLUSIONS
Ethinylestradiol/drospirenone initiators and initiators of other oral contraceptives are similarly likely to experience thromboembolism.


METHODS
II.
Seeger
John D
JD
i3 Drug Safety, Ingenix, Waltham, Massachusetts 02451, USA. jseeger@epidemiology.com
Loughlin
Jeanne
J
Eng
P Mona
PM
Clifford
C Robin
CR
Cutone
Jennifer
J
Walker
Alexander M
AM
D000293:Adolescent; D000328:Adult; D000736:Androstenes / Q000008:administration & dosage / Q000009:adverse effects*; D002648:Child; D015331:Cohort Studies; D003277:Contraceptives, Oral, Combined / Q000008:administration & dosage / Q000009:adverse effects*; D004997:Ethinyl Estradiol / Q000008:administration & dosage / Q000009:adverse effects*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D016016:Proportional Hazards Models; D018570:Risk Assessment; D012307:Risk Factors; D013923:Thromboembolism / Q000139:chemically induced* / Q000453:epidemiology
D000736:Androstenes; D003277:Contraceptives, Oral, Combined; D004997:Ethinyl Estradiol; C035144:drospirenone