Sertraline and Phenindione: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 2, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Sertraline
No brand names on recordPhenindione
No brand names on record
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
You've been prescribed sertraline (an antidepressant) along with phenindione (a blood thinner). Both can affect how easily you bleed. Sertraline changes how your platelets work, and phenindione slows down clotting, so putting them together can raise your chance of bleeding more than either one alone.
Watch for things like frequent nosebleeds, bruising more easily, tiny red spots on the skin, or bleeding that's hard to stop. Most people do fine, and your care team can manage this safely by keeping a closer eye on you. Please don't stop either medicine on your own. Just tell your pharmacist or doctor about any new or unusual bleeding.
Effect: Additive bleeding risk when sertraline is combined with phenindione (a vitamin K antagonist anticoagulant).
Mechanism: SSRIs deplete platelet serotonin, impairing platelet aggregation and primary hemostasis; this adds to phenindione's anticoagulant effect on secondary hemostasis. This is a pharmacodynamic interaction, not a prodrug or CYP-mediated one.
- Direction: increased anticoagulant/bleeding effect
- Onset: delayed
- Evidence: probable (case-control and cohort data)
- Severity: major
Management: Monitor for bleeding (epistaxis, ecchymosis, hematoma, petechiae, and serious hemorrhage). Anticoagulant dosing may need individualization; increase clinical vigilance during initiation and titration.
What happens
An increased risk of bleeding
Interaction Deep Dive
If sertraline is administered together with an anticoagulant, watch the patient for indications of heightened bleeding, and advise patients regarding this elevated bleeding risk 1. Platelet-mediated serotonin release plays a key role in preserving hemostasis. Studies using case-control and cohort designs have demonstrated that taking SSRIs (for example, sertraline) alongside anticoagulants carries an association with a greater bleeding risk 231. The simultaneous use of sertraline with an anticoagulant can heighten the likelihood of bleeding. Reported bleeding events have encompassed epistaxis, ecchymosis, hematoma, petechiae, and hemorrhages that are life-threatening 1.
Why it happens (mechanism)
Release of serotonin by platelets; additive effects on hemostasis
How to manage this interaction
The good news is your care team can manage this combination. Here is what usually happens and what you can do:
- Keep taking both exactly as prescribed unless your doctor or pharmacist tells you otherwise.
- Your team may monitor you more closely for bleeding, and your anticoagulant dose may need to be adjusted and individualized.
- Watch for and report nosebleeds, easy bruising, red skin spots, blood in urine or stool, or bleeding that won't stop.
- Get urgent help for severe or uncontrolled bleeding.
Bring up any new bleeding or bruising with your pharmacist or prescriber promptly.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
4 reports — tap to read
a) A retrospective cohort study (n=234) reported an elevated risk of clinically relevant bleeding (hospitalization due to bleeding) among patients taking warfarin for atrial fibrillation while also receiving SSRI therapy or within 2 weeks after stopping SSRI therapy. Patients with a mean age of 72 +/- 7 years who received warfarin plus SSRI (n=117) were matched with randomly chosen patients who received warfarin alone (n=117). The SSRIs included FLUoxetine, citalopram, PARoxetine, sertraline, fluvoxaMINE, or escitalopram. In the warfarin plus SSRI group, nine patients had 11 bleeding episodes over 213.9 treatment years, while in the warfarin-only group, 10 patients had 14 bleedings over 586.4 treatment years. The respective total bleeding incidences were 51.4 and 23.9 per 1000 treatment years. Compared with warfarin alone, the hazard ratio for first bleedings during warfarin plus SSRI treatment was 3.49 (95% CI; 1.37 to 8.91, p=0.009). The SSRIs involved in patients who bled during concurrent use were sertraline or citalopram. Adding an SSRI was not linked to any change in warfarin dose or INR (p=0.48 and p=0.31 respectively). The study findings may be constrained by prior bleeding events, uncertain patient adherence, and the omission of clopidogrel, dipyridamol, corticosteroids and anticoagulants other than warfarin from the model 2.
b) A population-based, case-controlled study of new coumarin users (acenocoumarol and phenprocoumon) taking selective serotonin reuptake inhibitors (SSRIs) at the same time found an increased risk of hospitalization from non-gastrointestinal bleeding. Drawing on national pharmacy and hospitalization records in the Netherlands, investigators identified 1848 cases admitted for abnormal bleeding and compared them with 5818 control subjects who were also using a coumarin. The median treatment duration in patients was 220 days (range, 1 to 4690 days). Patients receiving SSRIs had a higher risk of hospitalization for non-gastrointestinal bleeding (adjusted odds ratio (OR) 1.7, 95% confidence interval (CI), 1.1 to 2.5); however, the rate of gastrointestinal bleeding (adjusted OR 0.8, 95% CI, 0.4 to 1.5) did not differ significantly 3.
c) In a non-blinded, randomized, placebo-controlled trial with 12 healthy volunteers, the effect of sertraline on warfarin plasma protein binding was evaluated. On days and 32 of the study, all participants received warfarin 0.75 mg/kg. Starting on day 11, each volunteer was randomized to either the sertraline or placebo group; sertraline was increased gradually from 50 mg/day to 200 mg/day. Prothrombin time was measured before each warfarin dose and periodically afterward. The investigators concluded that sertraline did not enhance warfarin's anticoagulant effects to a clinically significant extent, even though sertraline was administered at a higher-than-usual dose 4.
d) Case reports and epidemiological studies (case-control and cohort studies) have shown an association between the use of drugs that interfere with serotonin reuptake and the occurrence of gastrointestinal bleeding. Based on data from published observational studies, exposure to SSRIs, especially in the month prior to delivery, has been associated with a less than 2-fold increase in the risk of postpartum hemorrhage. Bleeding events linked to SSRIs and SNRIs have ranged from ecchymosis, hematoma, epistaxis, and petechiae to life-threatening hemorrhages 1.
Common questions
Can I take Sertraline and Phenindione together?
Taking sertraline with phenindione raises your bleeding risk, so watch for bruising or bleeding and keep your care team informed; they can manage this with closer monitoring and dose adjustments. Do not stop either medicine on your own. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Sertraline and Phenindione interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How is the Sertraline and Phenindione interaction managed?
The good news is your care team can manage this combination. Here is what usually happens and what you can do: Keep taking both exactly as prescribed unless your doctor or pharmacist tells you otherwise. Your team may monitor you more closely for bleeding, and your anticoagulant dose may need to be adjusted and individualized. Watch for and report nosebleeds, easy bruising, red skin spots, blood i… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Sertraline or Phenindione need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (4)
- Product Information: ZOLOFT oral tablets, oral solution, sertraline hydrochloride oral tablets, oral solution. Viatris Specialty LLC (per FDA), Morgantown, WV, 2023. DailyMed
- Wallerstedt SM, Gleerup H, Sundstrom A, et al: Risk of clinically relevant bleeding in warfarin-treated patients-influence of SSRI treatment. Pharmacoepidemiol Drug Saf 2009; 18(5):412-416. DOI
- Schalekamp T, Klungel OH, Souverein PC, et al: Increased bleeding risk with concurrent use of selective serotonin reuptake inhibitors and coumarins. Arch Intern Med 2008; 168(2):180-185. PubMed
- Apseloff G, Wilner K, Gerber N, et al: Effect of sertraline on protien binding of warfarin. Clin Pharmacokinet 1997; 32 (suppl. 1):37-42.
Keep reading about Sertraline
Keep reading about Phenindione
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