Warfarin Institute of America

DEDICATED TO YOUR HEALTH SINCE 2000

Oral Contraceptive Use With Warfarin

Matt Thielbar, PharmD Candidate

University of Colorado School of Pharmacy Class of 2007

Oral birth control pills contain a combination of estrogen and progestin or progestin only.  There are concerns with both the estrogen and the some of the progestins in the pills.  The highest incidence of thromboembolism (venous blood clot resulting in a DVT or PE) occurs with combined oral contraceptives (COCs) with ≥ 50mcg of estrogen and “third generation” COCs containing the progestin desogestrel, gestodene, or norgestimate compared to other COCs.¹   Desogestrel carries a 2 to 5 times higher risk.3 Gestodene and norgestimate carry a 2 to 3 times higher risk.³ The progestin drosperinone is also thought to possess a greater risk of thrombosis than other COCs and some even believe that this has the highest risk.² 

COCs with greater risk of thromboembolism

References 1,2,3  

NuvaRing®

The NuvaRing is a progestin only vaginally inserted contraceptive.  The progestin contained in the ring is etonogestrel, which is the biologically active metabolite of desogestrel.⁴ This should be considered desogestrel and thus has a greater risk of thromboembolism compared to OCs with low estrogen and “safer” progestins.   

Ortho Evra®

OrthoEvra® is a transdermal system (“patch”) that delivers estrogen and progestin through the skin.  As the package insert states “You will be exposed to about 60% more estrogen if you use ORTHO EVRA than if you use a typical birth control pill containing 35 micrograms of estrogen.”⁵ The patch has a greater risk of thromboembolism compared to OCs with low estrogen and “safer” progestins. 

 COCs that have lower risk (i.e. have “safer” progestins in them”)

Necon® 1/35, Norinyl® 1 + 35, Nortrel® 1/35, Ortho-Novum® 1/35, Brevicon®, Modicon®, Necon® 0.5/35, Nortrel® 0.5/35, Ovcon-35®, Femcon Fe®, Balziva®, Demulen® 1/35, Kelnor® 1/35, Zovia® 1/35, Junel® 21 Day 1.5/30, Junel® Fe 1.5/30, Loestrin® 21 1.5/30, Loestrin® Fe 1.5/30, Microgestin® Fe 1.5/30, Cryselle® Lo/Ovral, Low-Ogestrel®, Jolessa®, Levlen®, Levora®, Nordette-28®, Portia®, Quasense®, Seasonale®, Alesse®, Aviane®, Lessina®, Levlite®, Lutera®, Sronyx®, Junel® 21 Day 1/20, Junel® Fe 1/20, Loestrin® 24 F, Loestrin® 21 1/20, Loestrin® Fe 1/20, Microgestin® Fe 1/20, Tri-Norinyl®, Aranelle®, Leena®, Necon® 7/7/7, Ortho-Novum®, 7/7/7®, Enpresse®, Tri-Levlen®, Triphasil®, Trivora®, Estrostep 21®, Estrostep Fe® 

Progestin only oral contraceptives

Progestin only oral contraceptives (“mini pill”) are safe to use with warfarin.  The minipills are not known to cause thromboembolisms.6  The progestin only oral contraceptives include; Camila®, Errin®, Jolivette®, Nor-QD®, Nora-BE®, Micronor®, Ovrette®.  A major problem with the mini pill is that you must take it at the same time everyday. If you take it 3 hours late it is considered a missed dose and you may not be protected from pregnancy.   

Thromboembolism

The rate of thromboembolism in healthy non-pregnant users for all OCs is; 4 cases in 100,000 woman-years (woman years means that if 100,000 women took OCs for one year; 4 would develop a thromboembolism), 10 – 15 cases in 100,000 woman-years in second generation (“safer”) OCs, and 20 – 30 cases in 100,000 woman-years for third generation OCs.³ The risk of a pregnant woman not using OCs is 60 cases in 100,000 woman years.³ 

Stroke

The relative risk (<1 = less risk, 1 = no difference, and >1 greater risk) of having a thrombotic (resulting from a clot) stroke while taking OCs ranges from 3 for normotensive (normal blood pressure) to 14 for severe hypertensive (high blood pressure) users.3 The relative risk of having a hemorrhagic stroke while taking OCs is 1.2 for nonsmokers, 7.6 for smokers, 1.8 for normotensives, 25.7 for severe hypertensives. For non-smokers who do not use OCs, the risk is 2.6.³ Note that if the relative risk is 8 that means that there is 8 times the risk compared to somebody not taking an OC.   

Oral Contraceptive Contraindications

“Thrombophlebitis; thromboembolic disorders (eg, valvular heart disease with thrombogenic complications); history of deep-vein thrombophlebitis; cerebral vascular disease; MI; coronary artery disease; known or suspected breast carcinoma or estrogen-dependent neoplasia; carcinoma of endometrium; hepatic adenomas/carcinomas(see Warnings); undiagnosed abnormal genital bleeding; known or suspected pregnancy (see Warnings); cholestatic jaundice of pregnancy/jaundice with prior pill use; hypersensitivity to any component of the product; acute liver disease; uncontrolled hypertension; headaches with focal neurological symptoms; diabetes with vascular complications; major surgery with prolonged immobility.”³ 

Alternatives to oral contraceptives

There are many alternative to oral contraceptives that are safe to use with warfarin such as; IUDs (copper (Paragard® - lasts 5 years) and also progestin (Mirena® - lasts 10 years), Depo Provera®, barrier methods (condom, cervical cap, diaphragm), and spermicidal jellies. Listed below is a table of pregnancy rates for various means of contraception for your information. 

Pregnancy Rates for Various Means of Contraception (%)*

* adapted from Facts and Comparisons

Conclusion

Any clotting disorder is considered a contraindication with the use of combined oral contraceptives. Ultimately this boils down to a risk vs benefit. In practice combined oral contraceptives are used in patients taking warfarin.  If you decided to use a COC, choosing one with less risk and discussion with your physician is recommended.  Progestin only oral contraceptives are a good alternative to COCs and do not have the risk of thromboembolism.  The other effective methods that could be used were listed and should be considered.  The rates of thromboembolism and stroke that were listed do not extrapolate to patients with previous history of clots. Patients with atrial fibrillation and mechanical heart valves are at risk for having a stroke.  The oral contraceptives have a much lower risk of causing a stroke that they do for causing a deep vein thrombosis or a pulmonary embolism.    

Measures should be taken to lower your risk of complication during hormonal contraceptive therapy such as controlling / preventing; high blood pressure, high cholesterol, obesity, and diabetes.  Smoking is a major risk factor and should not be done and especially if you are over the age of 35.  

References

1.         Clinical Pharmacology, (electronic version). Gold Standard, Tampa, FL, USA. Available at http://www.clinicalpharmacology.com (cited 12/5/06)

2.         Van Vliet HAAM, Winkel TA, Noort I, Rosing J, Rosendaal FR. Prothrombotic changes in users of combined oral contraceptives containing drospirenone and cyproterone acetate. J Thromb Haemost 2004; 2: 2060–2.

3.         Drug Facts and Comparisons [book online]. St. Louis (MO): Wolter Kluwer Health; v2006. Based on: Drug Facts and Comparisons 60^th edition. St. Louis (MO): Wolters Kluwer Health, 2007. Available at http://www.factsandcomparisons.com (cited 12/5/06)

4.         NuvaRing monograph. http://www.rxlist.com/cgi/generic4/nuvaring.htm

5.         OrthoEvra® [package insert]. Roseland NJ: Organon; 2006.

6.         Vasilakis C et al.: Risk of idiopathic venous thromboembolism in users of progestagens alone. Lancet 1999;354:1610-1611.

 ©2007 Matt Thielbar   Used by Permission

PLEASE ALSO LOOK AT FAMILY PLANNING WITH VENOUS THROMBOEMBOLISM

SEE A CATALOG OF PUBLICATIONS AVAILABLE FROM LODWICK CREATIONS, LLC.

LEARN HOW YOU CAN BECOME LISTED ON THE HONOR ROLL OF SUPPORTERS AND TAKE ADVANTAGE OF THE BENEFITS

REQUEST A MEDICATION CONSULTATION

DONATE USING PAYPAL

  Back to interactions list                        Home

© 2007 Lodwick Creations, LLC     

Contact Mr. Lodwick at: allodwick@earthlink.net

Last updated February 28, 2007