Relugolix and Hydroquinidine: 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
Hydroquinidine
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.
Let's talk about taking Orgovyx (relugolix) together with hydroquinidine. Both of these medicines can affect the timing of your heartbeat, something doctors call the QT interval. When two medicines that do this are taken together, the effect can add up and, in rare cases, lead to an abnormal heart rhythm.
This is a theoretical concern, meaning it's based on how these drugs work rather than lots of reported cases, but it's still worth taking seriously. The good news is your care team can manage this well by checking your heart rhythm with an EKG and keeping an eye on your blood minerals like potassium and magnesium. Please don't stop either medicine on your own, just talk with your doctor or pharmacist about the best plan for you.
Effect: Additive QT interval prolongation when relugolix is combined with hydroquinidine, a Class Ia antiarrhythmic and known QT-prolonging agent.
Mechanism: Pharmacodynamic (additive), not pharmacokinetic. Androgen deprivation from relugolix (GnRH antagonist) may itself prolong QT, compounding hydroquinidine's direct potassium-channel effect on repolarization.
- Direction: Increased proarrhythmic risk (TdP)
- Evidence: Theoretical; severity rated major
- Management: Avoid concomitant use when possible. If required, correct and avoid hypokalemia/hypomagnesemia, and perform periodic ECG and electrolyte monitoring. Weigh benefits of ADT against risk in congenital long QT, CHF, or recurrent 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 may 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 outweigh the possible hazards1. Where feasible, refrain from using relugolix alongside QT prolonging agents. Should coadministration be necessary, steer clear of drugs that produce electrolyte disturbances (that is, hypokalemia or hypomagnesemia)2, correct any electrolyte abnormalities, and consider periodic monitoring of ECGs and electrolytes1.
Why it happens (mechanism)
Additive QT interval prolongation
How to manage this interaction
Both medicines can lengthen the QT interval, so combining them may add to that effect. Here is how a care team typically handles this:
- Keep taking both as prescribed unless your doctor tells you otherwise.
- Your team may check periodic EKGs and blood tests for potassium and magnesium.
- They will work to correct any low potassium or magnesium, since these raise the risk.
- In some cases they may consider an alternative medicine, especially if you have a heart condition or a history of electrolyte problems.
Tell your pharmacist or doctor if you feel faint, dizzy, or notice a fluttering or irregular heartbeat, and share your full medication list.
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%) tied to ADT arose without concurrent use of other agents known to raise TdP risk; nevertheless, use of 1 drug and of 2 or more drugs carrying conditional, possible, or known TdP risk was reported in a portion of aLQTS/TdP events (23% or 43%) and sudden death events (18% and 22%). 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. The patients had a median age of about 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 on ADT chiefly for prostate cancer, with some treated for prostatism and androgenic alopecia. Most patients received ADT monotherapy (83%); 17% were on ADT combination therapy 3.
Common questions
Can I take Relugolix and Hydroquinidine together?
Relugolix and hydroquinidine can both prolong the QT interval, so together they raise the risk of an abnormal heart rhythm. Avoid the combination when possible, and if used together, have your heart rhythm and blood minerals monitored by your care team. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Relugolix and Hydroquinidine 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 Hydroquinidine interaction managed?
Both medicines can lengthen the QT interval, so combining them may add to that effect. Here is how a care team typically handles this: Keep taking both as prescribed unless your doctor tells you otherwise. Your team may check periodic EKGs and blood tests for potassium and magnesium. They will work to correct any low potassium or magnesium, since these raise the risk. In some cases they may consid… 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 Hydroquinidine 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 Hydroquinidine
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