Do New Birth Control Pills Increase Risk for Venous Thromboembolism?
BACKGROUND AND PURPOSE:
The traditional ‘cyclic’ regimen for combined oral contraceptives (COCs) is 21 days on and 7 days off
Current low-dose estrogen COC use (≤35 µg ethinyl estradiol) is associated with a 2- to 3-fold higher risk for venous thromboembolism (VTE)
This risk represents a small absolute excess risk which is much less than risk levels seen in pregnancy or postpartum
Li et al. (JAMA Internal Medicine, 2018) sought to determine the risk for venous thromboembolism (VTE) when COCs are used with continuous (365/0 days) or extended (84/7 days) regimens
Retrospective cohort study
US population identified from Sentinel Distributed Database
Administrative medical and prescription drug insurance claims and demographic data
18 to 50 years old at time of initiating use of COC
Excluded women with medical condition that could impact risk for VTE (e.g., prior VTE or malignancy)
Exposure was either
Traditional cyclic COCs
Initiators defined as
No use of the study COCs that were used to define each cohort during a 6-month lookback period
Medication contained ethinyl estradiol or levonorgestrel of any dose
Follow-up was index date until
Earliest occurrence of VTE hospitalization | Health plan disenrollment | Cessation of initiated COC | Initiation of a product of the other COC regimen in comparison or a nonstudy hormone contraceptive | Death | Pregnancy or live birth delivery | End of study period
Primary outcome: First VTE hospitalization that occurred during the study follow-up
Covariates were assessed for confounding including other drug use or medical conditions using propensity scoring
Compared to cyclic COCs, continuous/extended cyclic users had
Higher baseline cardiovascular and metabolic conditions (7.2% vs 4.7%)
More gynecological conditions (39.7% vs 32.3%)
Slightly higher health services utilization
Adjusting for confounding, there was a higher risk for VTE in the continuous/extended group (progestogen type levonorgestrel)
Hazard ratio 1.32 (95% CI, 1.07-1.64)
Adjusting for confounding, the absolute risk difference and the incidence rate difference between the 2 cohorts was low
Absolute risk difference: 0.27 per 1000 persons
Incidence rate difference: 0.35 cases per 1000 person-years
1.44 vs 1.09 cases per 1000 person-years
Continuous/extended COCs lead to slightly elevated VTE risk, compared to cyclic COCs
Authors consider the absolute risk to be small and likely not clinically significant and state
Accordingly, we do not recommend selective prescribing of COCs based on the cyclic and continuous/extended type. Clinicians should prescribe COCs based on patients’ individual risk factors and preferences.
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This educational activity may contain discussion of published and/or investigational uses of agents that are not indicated by the FDA. The planners of this activity do not recommend the use of any agent outside of the labeled indications.
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presented in this activity is not meant to serve as a guideline for patient management. Any procedures, medications, or other courses of diagnosis or treatment discussed or suggested in this activity should not be used by clinicians without evaluation of their patient’s conditions and possible contraindications and/or dangers in use, review of any applicable manufacturer’s product information, and comparison with recommendations of other authorities.
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