Arsenic Trioxide and Relugolix: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Relugolix
Arsenic Trioxide
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 two medicines that can each affect your heart's rhythm. Relugolix (Orgovyx) lowers testosterone as part of cancer treatment, and lowering it can slightly stretch out a part of your heartbeat called the QT interval. Arsenic trioxide (Trisenox) is also known to stretch that same interval. Taken together, the effects can add up, which in rare cases can lead to an irregular heartbeat.
This concern is based on how the drugs work rather than reports of it actually happening in people. The good news is your care team can manage this easily by checking your heart tracing (ECG) and blood minerals, and keeping them in a healthy range.
Additive QT prolongation is the concern with relugolix plus arsenic trioxide. Androgen deprivation from the GnRH antagonist relugolix can prolong the QT interval, and arsenic trioxide is an established QT-prolonging agent; combined pharmacodynamic effect increases torsades risk. Neither is a prodrug here; this is a PD interaction, not PK.
- Evidence: theoretical; severity: major; onset: unspecified.
- Management: avoid combination when feasible; weigh benefit of ADT in patients with congenital long QT, CHF, or electrolyte disturbances.
- If used together, correct and maintain K+ and Mg2+, avoid other agents causing hypokalemia/hypomagnesemia, and obtain periodic ECGs and electrolyte panels.
What happens
Increased risk of QT interval prolongation
Interaction Deep Dive
When relugolix is given together with agents 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 benefits of androgen deprivation therapy such as relugolix outweigh the possible risks3. Whenever feasible, do not use relugolix alongside QT prolonging agents. Should coadministration be necessary, refrain from using drugs that produce electrolyte disturbances (that is, hypokalemia or hypomagnesemia)1, correct any electrolyte abnormalities, and think about periodic monitoring of ECGs and electrolytes3.
Why it happens (mechanism)
Additive QT interval prolongation
How to manage this interaction
Both drugs can lengthen the QT interval, so your care team will watch your heart and blood minerals closely. Here is what typically happens and what you can do:
- Keep taking both exactly as prescribed unless your doctor tells you otherwise.
- Your team may order periodic ECGs (heart tracings) and blood tests to check potassium and magnesium, and correct them if low.
- They will consider whether the benefit of treatment outweighs the risk, especially if you have long QT syndrome, heart failure, or frequent electrolyte problems.
Tell your pharmacist or doctor about any fainting, dizziness, or a fluttering or racing heartbeat, and share a full list of your other medicines.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In an analysis of male patients on androgen deprivation therapy (ADT) using individual case safety reports from the international pharmacovigilance database VigiBase, investigators 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%) related to ADT arose without concurrent use of other agents recognized to elevate 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 classified 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 demonstrated 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. The median patient age was approximately 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 receiving ADT for prostate cancer, with some treated for prostatism and androgenic alopecia. Most patients were on ADT monotherapy (83%); 17% were receiving ADT combination therapy 2.
Common questions
Can I take Arsenic Trioxide and Relugolix together?
Combining relugolix and arsenic trioxide can add up to prolong the QT interval, so your care team may avoid the pairing when possible or monitor your ECG and electrolytes closely if both are needed. Report any fainting or palpitations right away. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Arsenic Trioxide 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 Arsenic Trioxide and Relugolix interaction managed?
Both drugs can lengthen the QT interval, so your care team will watch your heart and blood minerals closely. Here is what typically happens and what you can do: Keep taking both exactly as prescribed unless your doctor tells you otherwise. Your team may order periodic ECGs (heart tracings) and blood tests to check potassium and magnesium, and correct them if low. They will consider whether the ben… 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.
Questions for your pharmacist
- Does my dose of Arsenic Trioxide 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)
- 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
- Product Information: ORGOVYX oral tablets, relugolix oral tablets. Sumitomo Pharma America, Inc (per FDA), Marlborough, MA, 2025. DailyMed
Keep reading about Relugolix
Keep reading about Arsenic Trioxide
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