Warfarin with Desogestrel Interaction Details
Brand Names Associated with Warfarin
- Coumadin®
- Jantoven®
- Warfarin
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Nov 07, 2023
Interaction Effect
Decreased or increased anticoagulant effectiveness
Interaction Summary
Concomitant use of a combination contraceptive and warfarin may result in enhanced or reduced anticoagulant efficacy of warfarin. One study of 12 patients demonstrated an enhanced response to anticoagulant therapy when given concurrently with oral contraceptive . In one case report, warfarin dose adjustments were required with the concomitant use of 3 different hormonal contraceptives within a 1-year period . In another case report, emergency contraception with progestogen only in a patient receiving warfarin resulted in an enhanced anticoagulant effect evident by an INR of 8.1 . Although the mechanism of this interaction has not been determined, ethinyl estradiol inhibition of CYP1A2- and CYP2C19-mediated warfarin metabolism is the postulated primary mechanism . Therefore, prothrombin time and INR should be closely monitored when hormonal contraceptive and anticoagulants are coadministered.
Severity
Moderate
Onset
Delayed
Evidence
Probable
How To Manage Interaction
Concurrent use of warfarin and a combination oral contraceptive has the potential for decreased or increased anticoagulant efficacy. If these drugs are used together, consider closely monitor prothrombin time or INR.
Mechanism Of Interaction
Unknown
Literature Reports
A) Oral contraceptives potentiated anticoagulant efficacy, as measured by prothrombin time ratio, in 12 women (mean age, 34.5 yr) when treated concomitantly with a combination contraceptive (11, oral; 1, parenteral depot) and an anticoagulant (nicoumalone) compared with an anticoagulant alone. Anticoagulation was being used for Bjork-Shiley valvular prosthesis (n=9) and embolic mitral valve disease (n=3). Patients were followed for a total of 374 patient-months of which 230 months and 144 months were concomitant use with a mean anticoagulant dose of 2.05 mg (phase A) and anticoagulant alone at a mean dose of 2.53 mg (phase B), respectively. Although the anticoagulant dose requirement was lower during phase A (p less than 0.01), prothrombin time ratio was higher at 1.67 during phase A compared with 1.5 during phase B (p less than 0.01). It is postulated that the estrogens in the oral contraceptives may inhibit hepatic cell microsome enzymes. This may enhance the anticoagulant effect due to slowed breakdown of the anticoagulant .
B) Warfarin dose requirements were altered when 3 different hormonal contraceptives were used by a 33-year-old woman initially maintained on warfarin 38.5 mg/wk (historical max dose, 42 mg/wk) for long-term anticoagulation after aortic valve replacement. Monophasic ethinyl estradiol 0.02 mg/norethindrone 1 mg/day was also being given. Because of increased thrombosis risk, her oral contraceptive was replaced with an etonogestrel subdermal implant which required a 55.8% warfarin dose increase (60 mg/wk) to obtain goal INR (range, 2.5 to 3.5). After 10 months, the implant was removed due to increased menstrual bleeding. Nine days later, her INR increased to 6.5. During the next 48 days, no systemic contraceptives were used and her warfarin dose was titrated to 55.5 mg/wk. Oral norethindrone 0.35 mg/day was initiated and the warfarin dose stabilized at 53.5 mg/wk; however, norethindrone was discontinued 39 days later. Subsequently, no further warfarin dose adjustments were needed and the patient decided to avoid hormonal contraception. Ethinyl estradiol inhibition of CYP1A2- and CYP2C19-mediated warfarin metabolism is the postulated primary mechanism of this drug interaction which is considered probable based on the Horn Interaction Probability Scale .
C) A case report describes an enhanced anticoagulant effect of warfarin after giving a 35-year-old woman levonorgestrel for emergency contraception. The patient had familial type I (quantitative) antithrombin deficiency and a history of deep venous thrombosis and pulmonary thromboembolism. She had been stable on warfarin 7 mg per day with an INR) of 2.1. Three days after receiving emergency contraception, her INR was reported to be 8.1. Warfarin treatment was discontinued for two days and the patient's INR dropped to 2.5. No hemorrhagic complications occurred .
Warfarin Overview
-
Warfarin is used to prevent blood clots from forming or growing larger in your blood and blood vessels. It is prescribed for people with certain types of irregular heartbeat, people with prosthetic (replacement or mechanical) heart valves, and people who have suffered a heart attack. Warfarin is also used to treat or prevent venous thrombosis (swelling and blood clot in a vein) and pulmonary embolism (a blood clot in the lung). Warfarin is in a class of medications called anticoagulants ('blood thinners'). It works by decreasing the clotting ability of the blood.
Return To Our Drug Interaction Homepage
Feedback, Question Or Comment About This Information?
Ask Dr. Brian Staiger, PharmD, our medical editor, directly! He's always more than happy to assist.
Definitions
Severity Categories
Contraindicated
These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.
Major
This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.
Moderate
This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.
Minor
While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.
Onset
Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.
Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.
Evidence
Level of documentation of the interaction.
Established: The interaction is documented and substantiated in peer-reviewed medical literature.
Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.
How To Manage The Interaction
Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.
It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.
Mechanism Of Interaction
The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.
Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.
Where Does Our Information Come From?
Information for our drug interactions is compiled from several drug compendia, including:
The prescribing information for each drug, as published on DailyMED, is also used.
Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.
The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.