Further results on the risk of nonfatal venous thromboembolism in users of the contraceptive transdermal patch compared to users of oral contraceptives containing norgestimate and 35 microg of ethinyl estradiol

Abstract

Context: In 2006, we published a study that indicated that the new transdermal contraceptive patch containing ethinyl estradiol (EE) and the progestin norelgestromin did not increase the risk for venous thromboembolism (VTE) compared to oral contraceptive containing norgestimate and 35 microg of EE.

Objective: This report updates information on the risk of nonfatal VTE in women using the contraceptive patch in comparison to women using oral contraceptives containing norgestimate (either monophasic or triphasic) and 35 microg of EE (norgestimate-35) using an additional 17 months of data.

Design, setting and participants: Nested case-control design based on information from PharMetrics, a US-based company that collects and organizes information on claims paid by managed care plans. The study was nested among all women, aged 15 to 44 years, who started either the contraceptive patch or norgestimate-35 after April 1, 2002. Cases were women with current use of one of these two study drugs and a documented diagnosis of VTE in the absence of identifiable clinical risk factors (idiopathic VTE) who were not in the earlier study. Up to four controls were matched to each case by age and calendar time.

Main outcome measures: Odds ratios (ORs) comparing the risk of nonfatal VTE in new users of the two contraceptives.

Results: We identified 56 new cases of newly diagnosed, idiopathic VTE in the updated study population. The OR comparing the contraceptive patch to norgestimate-35 was 1.1 (95% CI 0.6-2.1).

Conclusions: After evaluating an additional 17 months of data, the results indicate that the risk of nonfatal VTE for the contraceptive patch is closely similar to the risk for oral contraceptives containing 35 mug of EE and norgestimate.