Relugolix and Isoflurane: 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
Isoflurane
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 these medicines can affect your heart's rhythm. Isoflurane is a gas used to keep you asleep during surgery. Relugolix (Orgovyx) is a pill used to treat prostate cancer by lowering testosterone. Each one can slightly stretch out a part of your heartbeat called the QT interval. When you have both together, that effect can add up, which in rare cases can lead to an abnormal heart rhythm.
The good news is that your care team knows about this. If you take relugolix and need surgery, your anesthesia and cancer teams can plan ahead, check your blood minerals, and watch your heart tracing. Always tell your surgical team about every medicine you take.
Additive QT prolongation. Both isoflurane (a volatile anesthetic with known QT-prolonging effect) and relugolix (a GnRH antagonist; androgen deprivation itself can prolong QT) can independently prolong the QT interval, producing an additive pharmacodynamic effect and increased torsades risk. Neither is a prodrug; this is a PD interaction, not metabolic.
- Evidence: theoretical; severity: major; onset: unspecified.
- Assess baseline risk: congenital long QT, CHF, electrolyte disturbances, other QT-prolonging agents.
- Avoid concomitant use when possible; if unavoidable, correct and maintain K+ and Mg2+, avoid agents causing hypokalemia/hypomagnesemia, and consider periodic ECG and electrolyte monitoring.
What happens
Increased risk of QT interval prolongation
Interaction Deep Dive
When relugolix is given together with agents 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 medications 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 alongside 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 your medicines as prescribed and make sure every provider (especially your surgical and anesthesia team) knows you take relugolix.
- Your team will weigh whether the benefit of relugolix outweighs the QT risk, especially if you have long QT syndrome, heart failure, or low potassium or magnesium.
- When possible, they may avoid combining relugolix with QT-prolonging drugs.
- If both are needed, they will correct any electrolyte imbalances and may check ECGs and blood electrolytes periodically.
Report symptoms like fainting, palpitations, or dizziness to your care team.
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) drawn from individual case safety reports in VigiBase, the international pharmacovigilance database, investigators identified 184 cases of acquired long-QT syndrome (aLQTS) and/or torsades de pointes (TdP; 11% of cases were fatal), 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 concurrent use of other agents recognized to raise TdP risk; nevertheless, use of 1 drug and of 2 or more drugs carrying conditional, possible, or known TdP risk was documented in a proportion 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 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 received ADT monotherapy (83%); 17% were on ADT combination therapy 3.
Common questions
Can I take Relugolix and Isoflurane together?
Isoflurane and relugolix can both prolong the QT interval, so combined use may add up and raise the risk of an abnormal heart rhythm; your care team can manage this by checking electrolytes and monitoring your heart. Make sure your surgical and anesthesia teams know you take relugolix. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Relugolix and Isoflurane 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 Isoflurane interaction managed?
Keep taking your medicines as prescribed and make sure every provider (especially your surgical and anesthesia team) knows you take relugolix. Your team will weigh whether the benefit of relugolix outweighs the QT risk, especially if you have long QT syndrome, heart failure, or low potassium or magnesium. When possible, they may avoid combining relugolix with QT-prolonging drugs. If both are neede… 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 Isoflurane 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 Isoflurane
Keep reading about Relugolix
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