PURLs

Prescribe This Combined OC With CV Safety in Mind

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WHAT’S NEW?

Low-dose estrogen + levonorgestrel confer lowest risk

Prior studies have shown that COCs increase the risk for PE and may also increase the risks for ischemic stroke and MI.3,11 Studies have also suggested that a higher dose of estrogen in COCs is associated with an increased risk for VTE.11,12 This study shows that 20 µg of estrogen combined with levonorgestrel is associated with the lowest risks for PE, MI, and ischemic stroke.

CAVEATS

Cohort study, no start date, incomplete tobacco use data

This is an observational cohort study, so it is subject to confounding factors and biases. It does, however, include a very large population, which improves validity. The study did not account for COC start date, which may be confounding because the risk for VTE is highest in the first three months to one year of COC use.12 Data on tobacco use, a significant independent risk factor for arterial but not venous thromboembolism, was incomplete; however, in other studies, it has only marginally affected outcomes.3,13

CHALLENGES TO IMPLEMENTATION

Increased vaginal spotting

One potential challenge to implementing this practice changer may be the increased rate of vaginal spotting associated with low-dose estrogen. COCs containing 20 µg of estrogen are associated with spotting in approximately two-thirds of menstrual cycles over the course of a year.14 That said, women may prefer to endure the spotting in light of the improved safety profile of a lower-dose estrogen pill.

ACKNOWLEDGEMENT

The PURLs Surveillance System was supported in part by Grant Number UL1RR024999 from the National Center For Research Resources, a Clinical Translational Science Award to the University of Chicago. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Center For Research Resources or the National Institutes of Health.

Copyright © 2017. The Family Physicians Inquiries Network. All rights reserved.

Reprinted with permission from the Family Physicians Inquiries Network and The Journal of Family Practice (2017;66[7]:454-456).

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