Relugolix and Procainamide: 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
Procainamide
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. Procainamide is a heart-rhythm drug that can stretch out part of your heartbeat (called the QT interval). Relugolix (Orgovyx), used for prostate cancer, can also do this because lowering testosterone may affect the QT interval. Taking both together can add up, which in rare cases could lead to a dangerous irregular heartbeat.
Please don't stop either medicine on your own. This is something your care team knows how to handle. They may keep a closer eye on your heart tracing (ECG) and your blood minerals, and they can adjust things as needed. Just let them know you're taking both.
Effect: Additive QT interval prolongation with increased risk of torsades de pointes.
Mechanism: Both agents prolong the QT interval by independent pathways. Procainamide is a Class Ia antiarrhythmic with known QT-prolonging (and QRS-widening) effects; relugolix-induced androgen deprivation may also prolong QT. Effect is pharmacodynamic (additive), not metabolic. Neither is a prodrug relevant here.
Evidence: Theoretical; severity major; onset unspecified.
Management:
- Avoid concomitant use where possible; weigh benefits of ADT.
- Use caution in congenital long QT, CHF, or recurrent electrolyte disturbance.
- Correct and avoid hypokalemia/hypomagnesemia.
- Consider periodic ECG and electrolyte monitoring.
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. Androgen deprivation resulting from GnRH agonists or antagonists can itself lengthen the QT interval. In patients who have congenital long QT syndrome, congestive heart failure, or recurrent electrolyte abnormalities, as well as those receiving drugs recognized for prolonging the QT interval, weigh whether the benefits of androgen deprivation therapy such as relugolix are greater than the possible risks1. Where feasible, do not use relugolix at the same time as QT prolonging agents. When coadministration cannot be avoided, refrain from using medications that produce electrolyte abnormalities (that is, hypokalemia or hypomagnesemia) 2, correct any electrolyte abnormalities, and consider intermittent monitoring of ECGs and electrolytes 1.
Why it happens (mechanism)
Additive QT interval prolongation
How to manage this interaction
Both drugs can affect your heart's rhythm, so your care team may take steps to keep you safe. Keep taking both exactly as prescribed unless your prescriber tells you otherwise.
Your team may:
- Decide whether the benefit of relugolix outweighs the risk, especially if you have a heart-rhythm condition or heart failure.
- Check and correct your blood minerals (potassium and magnesium) and avoid drugs that lower them.
- Do periodic ECGs and blood tests to watch your heart.
Tell your pharmacist or doctor about all your medicines, and report any fainting, dizziness, or a fluttering or pounding heartbeat right away.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) A study assessed male patients undergoing androgen deprivation therapy (ADT) using individual case safety reports from VigiBase, the international pharmacovigilance database, and found 184 reports of acquired long-QT syndrome (aLQTS) and/or torsades de pointes (TdP; 11% of which were fatal), along with 99 reports 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 use 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 analyzed, 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 mainly receiving ADT for prostate cancer, with some treated for prostatism and androgenic alopecia. The majority of patients were on ADT monotherapy (83%); 17% were on ADT combination therapy 3.
Common questions
Can I take Relugolix and Procainamide together?
Taking relugolix and procainamide together can add up to prolong the QT interval and raise the risk of a serious irregular heartbeat, so your care team should watch you closely with ECGs and electrolyte checks. Don't stop either drug on your own; ask your pharmacist or doctor. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Relugolix and Procainamide 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 Procainamide interaction managed?
Both drugs can affect your heart's rhythm, so your care team may take steps to keep you safe. Keep taking both exactly as prescribed unless your prescriber tells you otherwise. Your team may: Decide whether the benefit of relugolix outweighs the risk, especially if you have a heart-rhythm condition or heart failure. Check and correct your blood minerals (potassium and magnesium) and avoid drugs th… 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 Procainamide 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 Procainamide
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