Paroxetine with Warfarin Interaction Details

Brand Names Associated with Paroxetine

Brand Names Associated with Warfarin

Medical Content Editor Dr. Brian Staiger, PharmD
Last updated Nov 13, 2023

Interaction Effect

An increased risk of bleeding and an increased free concentration of PARoxetine or warfarin

Interaction Summary

A cohort study demonstrated that the combined use of SSRIs and anticoagulants has been associated with an increased risk of bleeding. Bleeding events reported have included epistaxis, ecchymosis, hematoma, petechiae, and life-threatening hemorrhages. Concomitant use of PARoxetine with warfarin (an anticoagulant) may potentiate the risk of bleeding; monitor patients for signs of increased bleeding. The INR should be monitored closely. Additionally, both PARoxetine and warfarin are highly bound to plasma proteins, which may lead to an increase in free concentrations of either drug. Monitor for adverse reactions and reduce dosage of PARoxetine or warfarin as indicated . Closely monitor for bleeding in patients receiving warfarin when paroxetine is initiated or discontinued .

Severity

Major

Onset

Delayed

Evidence

Theoretical

How To Manage Interaction

Concomitant use of PARoxetine with warfarin (an anticoagulant) may potentiate the risk of bleeding; monitor patients for signs of increased bleeding. The INR should be monitored closely. Additionally, both PARoxetine and warfarin are highly bound to plasma proteins, which may lead to an increase in free concentrations of either drug. Monitor for adverse reactions and reduce dosage of PARoxetine or warfarin as indicated. Closely monitor for bleeding in patients receiving warfarin when paroxetine is initiated or discontinued .

Mechanism Of Interaction

Release of serotonin by platelets; additive effects on hemostasis; highly bound to plasma protein

Literature Reports

A) According to a retrospective cohort study (n=234), there was an increased risk of clinically relevant bleeding (hospital admission due to bleeding) in patients receiving warfarin for atrial fibrillation during concomitant SSRI therapy or within 2 weeks following SSRI therapy termination. Patients with a mean age of 72 +/- 7 years receiving warfarin plus SSRI (n=117) were matched with randomly selected patients who received warfarin only (n=117). SSRI included FLUoxetine, citalopram, PARoxetine, sertraline, fluvoxaMINE, or escitalopram. Nine patients experienced 11 bleeding episodes during 213.9 treatment years in the warfarin plus SSRI group, and 10 patients experienced 14 bleedings during 586.4 treatment years in the warfarin-only group. The corresponding total incidences of bleedings were 51.4 and 23.9 per 1000 treatment years, respectively. The hazard ratio for first bleedings during treatment with warfarin plus SSRI was 3.49 (95% CI; 1.37 to 8.91, p=0.009) compared with warfarin only. The SSRI implicated in patients experiencing bleeding at the time of concomitant administration were sertraline or citalopram. The addition of an SSRI was not associated with a change in warfarin dose or INR (p=0.48 and p=0.31 respectively). The results of the study may be limited by earlier bleeding events, unknown patient adherence, and exclusion of clopidogrel, dipyridamol, corticosteroids and anticoagulants other than warfarin in the model .

B) Preliminary data suggest that there may be a pharmacodynamic interaction (that causes an increased bleeding diathesis with unaltered prothrombin time) between PARoxetine and warfarin. The concomitant use of PARoxetine and warfarin should be undertaken with caution .

C) In a multiple-dose study, several days of combined therapy with warfarin and PARoxetine resulted in mild but clinically significant bleeding in 5 of 27 subjects. This effect occurred in the absence of a significant enhancement in warfarin-induced hypoprothrombinemia or changes in either PARoxetine or warfarin disposition .

Paroxetine Overview

• Paroxetine tablets, suspension (liquid), and extended-release (long-acting) tablets are used to treat depression, panic disorder (sudden, unexpected attacks of extreme fear and worry about these attacks), and social anxiety disorder (extreme fear of interacting with others or performing in front of others that interferes with normal life). Paroxetine tablets and suspension are also used to treat obsessive-compulsive disorder (bothersome thoughts that won't go away and the need to perform certain actions over and over), generalized anxiety disorder (GAD; excessive worrying that is difficult to control), and posttraumatic stress disorder (disturbing psychological symptoms that develop after a frightening experience). Paroxetine extended-release tablets are also used to treat premenstrual dysphoric disorder (PMDD, physical and psychological symptoms that occur before the onset of the menstrual period each month). Paroxetine capsules (Brisdelle) are used to treat hot flashes (sudden feelings of warmth, especially in the face, neck, and chest) in women who are experiencing menopause (stage of life when menstrual periods become less frequent and stop and women may experience other symptoms and body changes). Paroxetine is in a class of medications called selective serotonin-reuptake inhibitors (SSRIs). It treats depression and other mental illnesses by increasing the amount of serotonin, a natural substance in the brain that helps maintain mental balance. There is not enough information available at this time to know how paroxetine works to treat hot flashes.

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.

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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:

• Gold Standard Drug Database
• Micromedex
• Lexicomp
• DrugBank

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.