Relugolix and Sodium Phosphate, Monobasic: 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
Sodium Phosphate, Monobasic
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.
You've been prescribed two medicines that can each affect your heart's rhythm. Relugolix (Orgovyx) lowers testosterone as part of prostate cancer treatment, and lowering testosterone can slightly change the heart's electrical timing (called the QT interval). Sodium phosphate is often used to clean out the bowel, and it can shift your body's minerals (like potassium and magnesium), which can also affect that same heart timing.
Together, they could add up. The good news is this is a possible risk, not a sure thing, and your care team can manage it easily by checking your minerals and, if needed, an EKG. Please keep taking both as prescribed and just talk with your pharmacist or doctor about your heart history.
Effect: Additive QT-interval prolongation (PD interaction, not metabolic). Androgen deprivation from relugolix can prolong QT; sodium phosphate bowel prep can cause electrolyte shifts (hypokalemia, hypomagnesemia) that further increase QT risk.
Direction: Increased proarrhythmic risk. Neither is a prodrug; the concern is pharmacodynamic plus electrolyte-mediated.
Evidence: Theoretical. Onset: unspecified.
Management:
- Weigh benefit vs risk in congenital long QT, CHF, or frequent electrolyte disturbances.
- Avoid concomitant use where possible.
- If required, correct and avoid worsening 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. The androgen deprivation produced by GnRH agonists and 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 risks 1. Whenever feasible, do not use relugolix alongside QT prolonging agents. Should combined administration be necessary, steer clear of drugs that produce electrolyte disturbances (that is, hypokalemia or hypomagnesemia) 2, correct any electrolyte disturbances, and think about periodic ECG and electrolyte monitoring 1.
Why it happens (mechanism)
Additive QT interval prolongation
How to manage this interaction
This risk is manageable, and your care team has clear ways to keep you safe.
- Keep taking both as prescribed unless your doctor or pharmacist tells you otherwise.
- Your team may check your potassium and magnesium levels and correct them if they are low, since low minerals raise heart-rhythm risk.
- They may order a periodic EKG to watch your heart's timing.
- Where possible, your team may choose to avoid using them together or adjust timing.
Tell your prescriber if you have a history of long QT syndrome, heart failure, or frequent electrolyte problems, and report any fainting, dizziness, or palpitations.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) A study looked at male patients undergoing androgen deprivation therapy (ADT) using individual case safety reports from VigiBase, the international pharmacovigilance database, and 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%) associated with ADT arose without exposure to other drugs known to elevate TdP risk; nevertheless, exposure to 1 drug and to 2 or more drugs carrying conditional, possible, or known TdP risk was reported in a portion of aLQTS/TdP (23% or 43%) and sudden death (18% and 22%) events. The drugs 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 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 taking ADT mainly for prostate cancer, with some treated for prostatism and androgenic alopecia. Most patients were on ADT monotherapy (83%); 17% were receiving ADT combination therapy 3.
Common questions
Can I take Relugolix and Sodium Phosphate, Monobasic together?
Combining relugolix with sodium phosphate can add up to a higher risk of heart-rhythm (QT) changes, mainly through mineral shifts. Keep taking both as prescribed and ask your care team about checking your electrolytes and an EKG, especially if you have any heart history. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Relugolix and Sodium Phosphate, Monobasic 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 Sodium Phosphate, Monobasic interaction managed?
This risk is manageable, and your care team has clear ways to keep you safe. Keep taking both as prescribed unless your doctor or pharmacist tells you otherwise. Your team may check your potassium and magnesium levels and correct them if they are low, since low minerals raise heart-rhythm risk. They may order a periodic EKG to watch your heart's timing. Where possible, your team may choose to avoi… 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 Sodium Phosphate, Monobasic 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
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