Tamoxifen and Relugolix: 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
Relugolix
Tamoxifen
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.
Both relugolix and tamoxifen can affect the timing of your heartbeat. Doctors call this QT prolongation, a small change in the heart's electrical rhythm. When two medicines that both do this are taken together, the effect can add up and, rarely, lead to an irregular heartbeat.
The good news is this concern is mostly theoretical, meaning it comes from how these drugs work rather than from lots of real-world problems. Your care team can manage it easily by checking things like an occasional heart tracing (ECG) and your blood minerals. Please keep taking both exactly as prescribed and talk with your pharmacist or doctor about any dizziness, fainting, or palpitations.
Effect: Additive QT interval prolongation. Both agents independently prolong the QT interval (androgen deprivation from relugolix; tamoxifen has documented QT effects), so combined use raises torsades risk theoretically.
- Mechanism: Pharmacodynamic additive QT prolongation (not a metabolic/PK interaction).
- Direction: Increased cardiac risk; neither is a relevant prodrug here.
- Evidence: Theoretical; severity major; onset unspecified.
- Management: Avoid concomitant use when possible. If required, correct and avoid hypokalemia/hypomagnesemia, and consider periodic ECG and electrolyte monitoring. Weigh benefit of ADT against risk in congenital long QT, CHF, or frequent electrolyte disturbances.
What happens
Increased risk of QT interval prolongation
Interaction Deep Dive
When relugolix is given together with medications that prolong the QT interval, the effects on the QT interval are additive. The androgen deprivation produced by GnRH agonists and antagonists can lengthen the QT interval. In patients who have congenital long QT syndrome, congestive heart failure, or recurrent electrolyte disturbances, as well as in those receiving drugs recognized to prolong the QT interval, weigh whether the advantages of androgen deprivation therapy such as relugolix outweigh the possible hazards1. Where feasible, do not use relugolix alongside QT prolonging agents. When coadministration cannot be avoided, refrain from using drugs that produce electrolyte abnormalities (that is, hypokalemia or hypomagnesemia) 2, correct any electrolyte abnormalities, and consider periodic monitoring of ECGs and electrolytes 1.
Why it happens (mechanism)
Additive QT interval prolongation
How to manage this interaction
Your care team can manage this combination safely with a few simple steps:
- Keep taking both as prescribed unless your doctor tells you otherwise.
- Your team may order periodic ECGs (heart tracings) and blood tests for electrolytes like potassium and magnesium.
- Low potassium or magnesium can raise the risk, so these are corrected if found.
- Your doctor may weigh whether an alternative is appropriate, especially if you have a history of heart rhythm problems, heart failure, or frequent electrolyte issues.
Call your pharmacist or prescriber promptly if you notice fainting, palpitations, or unusual dizziness.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) A study assessing male patients on androgen deprivation therapy (ADT) using individual case safety reports from the international pharmacovigilance database VigiBase identified 184 cases of acquired long-QT syndrome (aLQTS) and/or torsades de pointes (TdP; 11% fatal cases), along with 99 cases of sudden death linked to ADT. The majority of aLQTS/TdP cases (62%) and sudden death cases (88%) associated with ADT arose without concurrent use of other agents known to raise TdP risk; nevertheless, use of 1 drug and 2 or more drugs carrying conditional, possible, or known TdP risk was documented in a portion of aLQTS/TdP (23% or 43%) and sudden death (18% and 22%) events. The agents regarded as ADTs included abiraterone, gonadotropin-releasing hormone agonists and antagonists, nonsteroidal androgen receptor inhibitors indicated for prostate cancer, and 5-alpha-reductase inhibitors indicated for androgenic alopecia and prostatism. Among the 10 ADTs assessed, 7 showed a disproportional association (reporting odds ratio, 1.4 to 4.7) with aLQTS, TdP, or sudden death, namely leuprorelin, goserelin, triptorelin, degarelix, bicalutamide, finasteride, and dutasteride. Patients had a median age of roughly 76 years, and the median time to onset was 170 days (range, 7 to 4884 days) for aLQTS/TdP events and 92 days (range, 0.25 to 4984 days) for sudden death events. Patients were primarily taking ADT for prostate cancer, with some treated for prostatism and androgenic alopecia. The majority were on ADT monotherapy (83%); 17% were receiving ADT combination therapy 3.
Common questions
Can I take Tamoxifen and Relugolix together?
Relugolix and tamoxifen can both stretch the heart's QT interval, and together the effect may add up, so your care team may monitor your ECG and electrolytes. Keep taking both as prescribed and report any fainting or palpitations. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Tamoxifen and Relugolix interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Tamoxifen and Relugolix interaction managed?
Your care team can manage this combination safely with a few simple steps: Keep taking both as prescribed unless your doctor tells you otherwise. Your team may order periodic ECGs (heart tracings) and blood tests for electrolytes like potassium and magnesium. Low potassium or magnesium can raise the risk, so these are corrected if found. Your doctor may weigh whether an alternative is appropriate,… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Tamoxifen or Relugolix 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 (3)
- Product Information: ORGOVYX oral tablets, relugolix oral tablets. Sumitomo Pharma America, Inc (per FDA), Marlborough, MA, 2025. DailyMed
- Lyon AR, Lopez-Fernandez T, Couch LS, et al: 2022 ESC guidelines on cardio-oncology developed in collaboration with the European Hematology Association (EHA), the European Society for Therapeutic Radiology and Oncology (ESTRO) and the International Cardio-Oncology Society (IC-OS). Eur Heart J 2022; 43(41):4229-4361.
- Salem JE, Yang T, Moslehi JJ, et al: Androgenic effects on ventricular repolarization: a translational study from the international pharmacovigilance database to iPSC-cardiomyocytes. Circulation 2019; 140(13):1070-1080. PubMed
Keep reading about Relugolix
Keep reading about Tamoxifen
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist