Relugolix and Ribociclib: 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
Ribociclib
Relugolix
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 ribociclib (Kisqali) and relugolix (Orgovyx) can affect your heart's electrical rhythm in the same way. Each one can stretch out a part of your heartbeat called the QT interval. When you take them together, that effect can add up, which in rare cases could lead to an irregular heartbeat.
This concern is based mostly on how these drugs work, not on lots of reported cases, so try not to worry. Your care team can manage it by keeping an eye on your heart with an ECG and checking your blood levels of potassium and magnesium. Please don't stop either medicine on your own. Just talk with your doctor or pharmacist, especially if you feel dizzy, faint, or have a fluttering heartbeat.
Effect: Additive QT interval prolongation from concurrent ribociclib and relugolix. Both agents are independently associated with QTc prolongation (ribociclib is a known QT-prolonging CDK4/6 inhibitor; androgen deprivation from GnRH antagonists like relugolix may also prolong QT).
- Mechanism: Pharmacodynamic (additive), not a metabolic/prodrug interaction.
- Evidence: Theoretical; severity rated major.
- Onset: Unspecified.
- Management: Avoid combination when possible. If required, correct and avoid hypokalemia/hypomagnesemia, and perform periodic ECG and electrolyte monitoring. Use added caution 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 or antagonists can itself lengthen the QT interval. In patients who have congenital long QT syndrome, congestive heart failure, or recurrent electrolyte disturbances, as well as those receiving drugs recognized to prolong the QT interval, weigh whether the advantages of androgen deprivation therapy such as relugolix are greater than the possible hazards 1. Where feasible, do not use relugolix concurrently with QT prolonging agents. Should coadministration be necessary, refrain from using drugs that produce electrolyte disturbances (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
Keep taking both medications exactly as prescribed unless your care team tells you otherwise. Because both can lengthen the QT interval, your team may take steps to keep this safe.
- Your prescriber may weigh the benefits of relugolix against the risk, especially if you have a heart rhythm condition, heart failure, or frequent electrolyte problems.
- They may order periodic ECGs and check potassium and magnesium levels, correcting any that are low.
- Where possible, the team may avoid other drugs that lower electrolytes.
Tell your pharmacist or doctor right away if you feel fainting, dizziness, or an irregular or pounding heartbeat.
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 VigiBase, the international pharmacovigilance database, investigators found 184 cases of acquired long-QT syndrome (aLQTS) and/or torsades de pointes (TdP; 11% of which were fatal), along with 99 cases of sudden death linked to ADT. The majority of aLQTS/TdP (62%) and sudden death (88%) cases connected to 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 some 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 approved for prostate cancer, and 5-alpha-reductase inhibitors approved 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. 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 taking ADT chiefly for prostate cancer, with some treated for prostatism and androgenic alopecia. The majority of patients were on ADT monotherapy (83%); 17% were receiving ADT combination therapy 3.
Common questions
Can I take Relugolix and Ribociclib together?
Taking ribociclib and relugolix together can add up their effects on your heart rhythm (QT prolongation), so your care team may monitor ECGs and electrolytes and use caution; keep taking both as prescribed and report any fainting or irregular heartbeat. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Relugolix and Ribociclib 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 Relugolix and Ribociclib interaction managed?
Keep taking both medications exactly as prescribed unless your care team tells you otherwise. Because both can lengthen the QT interval, your team may take steps to keep this safe. Your prescriber may weigh the benefits of relugolix against the risk, especially if you have a heart rhythm condition, heart failure, or frequent electrolyte problems. They may order periodic ECGs and check potassium an… 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 Relugolix or Ribociclib 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 Ribociclib
Keep reading about Relugolix
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Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
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