Relugolix and Mobocertinib: 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
Mobocertinib
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 of your medicines, mobocertinib (Exkivity) and relugolix (Orgovyx), can affect the timing of your heartbeat. Doctors call this QT prolongation. When two medicines that do this are taken together, the effect can add up, which can slightly raise the chance of an abnormal heart rhythm.
The good news is this is a known, manageable issue. Your care team may check your heart rhythm with an EKG and keep an eye on blood minerals like potassium and magnesium. Please don't stop either medicine on your own. Talk with your pharmacist or doctor so they can watch you closely and keep both drugs working safely for you.
Effect: Additive QT-interval prolongation with combined mobocertinib and relugolix. Both agents independently carry QT-prolonging potential (relugolix via androgen deprivation; mobocertinib is a documented QT-prolonging TKI), so risk of QTc prolongation and torsades is increased. Neither is a prodrug relevant here; this is a pharmacodynamic, not metabolic, interaction.
- Severity/Evidence: Major; theoretical/additive mechanism.
- Onset: Unspecified.
- Management: Avoid concomitant use where possible. If required, correct and avoid causing hypokalemia/hypomagnesemia, and perform periodic ECG and electrolyte monitoring. Weigh benefit of therapy 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 or antagonists can lengthen the QT interval. In patients who have congenital long QT syndrome, congestive heart failure, or recurrent electrolyte disturbances, as well as those receiving medications recognized to prolong the QT interval, weigh whether the advantages of androgen deprivation therapy such as relugolix are greater than the possible hazards1. Where feasible, do not use relugolix alongside QT prolonging agents. Should coadministration be necessary, refrain from using medications that produce electrolyte disturbances (that is, hypokalemia or hypomagnesemia)2, correct any electrolyte disturbances, and consider periodic ECG and electrolyte monitoring1.
Why it happens (mechanism)
Additive QT interval prolongation
How to manage this interaction
Your care team can manage this by watching your heart and blood levels while you take both medicines.
- Keep taking both as prescribed unless your doctor tells you otherwise.
- Your team may order periodic EKGs and check potassium and magnesium levels, correcting them if low.
- They may avoid or limit other medicines that lower those minerals or prolong QT.
- Tell your doctor if you have a history of heart rhythm problems, heart failure, or long QT syndrome.
Report any fainting, dizziness, palpitations, or irregular heartbeat to your pharmacist or doctor right away.
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 identified 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 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 of 2 or more drugs carrying conditional, possible, or known TdP risk was documented in a portion of aLQTS/TdP events (23% or 43%) and sudden death events (18% and 22%). 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 mainly receiving ADT for prostate cancer, with some treated for prostatism and androgenic alopecia. Most patients were on ADT monotherapy (83%); 17% were on ADT combination therapy 3.
Common questions
Can I take Relugolix and Mobocertinib together?
Taking mobocertinib and relugolix together can add up their effects on your heart rhythm (QT prolongation), so your care team may monitor your EKG and electrolytes; keep taking both as prescribed and report any dizziness, fainting, or palpitations. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Relugolix and Mobocertinib 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 Mobocertinib interaction managed?
Your care team can manage this by watching your heart and blood levels while you take both medicines. Keep taking both as prescribed unless your doctor tells you otherwise. Your team may order periodic EKGs and check potassium and magnesium levels, correcting them if low. They may avoid or limit other medicines that lower those minerals or prolong QT. Tell your doctor if you have a history of hear… 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 Mobocertinib 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 Mobocertinib
Keep reading about Relugolix
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