Warfarin with Quetiapine Interaction Details
Brand Names Associated with Warfarin
- Coumadin®
- Jantoven®
- Warfarin
Brand Names Associated with Quetiapine
- Quetiapine
- Seroquel®
- Seroquel® XR
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Nov 08, 2023
Interaction Effect
Increased INR and risk for bleeding
Interaction Summary
Concomitant use of quetiapine together with warfarin may result in increased INR and risk of bleeding. Two case reports have described elevations in INR following addition of quetiapine in patients previously stable on warfarin, one of which included a patient who was diagnosed with warfarin-associated multiple intracerebral hemorrhages (ICH). Monitor INR when starting, stopping, or changing the dose of the concomitant drug in patients receiving warfarin therapy .
Severity
Moderate
Onset
Delayed
Evidence
Probable
How To Manage Interaction
Concomitant use of quetiapine together with warfarin may result in increased INR and risk of bleeding. Monitor INR when starting, stopping, or changing the dose of the concomitant drug in patients receiving warfarin therapy .
Mechanism Of Interaction
Unknown
Literature Reports
A) Increased INR and multiple intracerebral hemorrhages (ICH) was reported approximately 3 days after initiation of quetiapine in a 78-year-old man who had a stable INR for 1 year prior with warfarin. The patient, who had a history of coronary artery disease, hypertension, and dementia, was started on quetiapine 12.5 mg/day for agitation and delusions in the prior 2 months. Concomitant medications included atenolol 50 mg/day, lacidipine 4 mg/day, and donepezil 5 mg/day. Approximately 3 days after quetiapine initiation, the patient presented with an abrupt onset of varying levels of consciousness, dizziness, and headache. Laboratory evaluation revealed INR of 3.54, and a head CT revealed foci at the left posterolateral temporal lobe (34 mm), right lateral temporal (17.3 mm), left high parietal (14 mm) and deep left cerebellar hemisphere (25 mm); leading to a diagnosis of warfarin-associated multiple ICH. Quetiapine and warfarin were discontinued, and the INR fell to 1.04. No changes were identified in the recent dietary or bowel habits of the patient. Drug Interaction Probability Scale of 6 (0- to 11-point scale) indicated a probable interaction between quetiapine and warfarin .
B) A 71-year-old woman experienced enhanced anticoagulant effects from warfarin when quetiapine was added to her drug regimen. Her medications included phenytoin 300 mg daily with a serum concentration of 9.87 mg/L, warfarin 19.5 mg weekly with an INR of 2.6, benztropine 0.5 mg daily, and olanzapine 20 mg daily. Olanzapine was discontinued, and quetiapine therapy was initiated at 200 mg daily. Five days later, the INR was 2.7. After two weeks of quetiapine treatment, the INR increased to 9.2. Quetiapine was discontinued and two doses of vitamin K 10 mg were administered. The only clinical signs observed in the patient were a small amount of bleeding at the site of the vitamin K injection and a bruise on the hand. The INR decreased back to baseline with the discontinuation of quetiapine .
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.
Quetiapine Overview
-
Quetiapine tablets and extended-release (long-acting) tablets are used to treat the symptoms of schizophrenia (a mental illness that causes disturbed or unusual thinking, loss of interest in life, and strong or inappropriate emotions). Quetiapine tablets and extended-release tablets are also used alone or with other medications to treat episodes of mania (frenzied, abnormally excited or irritated mood) or depression in patients with bipolar disorder (manic depressive disorder; a disease that causes episodes of depression, episodes of mania, and other abnormal moods). In addition, quetiapine tablets and extended-release tablets are used with other medications to prevent episodes of mania or depression in patients with bipolar disorder. Quetiapine extended-release tablets are also used along with other medications to treat depression. Quetiapine tablets may be used as part of a treatment program to treat bipolar disorder and schizophrenia in children and teenagers. Quetiapine is in a class of medications called atypical antipsychotics. It works by changing the activity of certain natural substances in the brain.
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.