Relugolix and Formoterol: 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
Formoterol
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 electrical rhythm. Relugolix (Orgovyx) is a hormone-lowering medicine, and lowering testosterone can slightly stretch out a part of the heartbeat called the QT interval. Formoterol (Perforomist), a breathing medicine, can do the same thing. Taken together, those small effects can add up and, rarely, lead to an irregular heartbeat.
This is a theoretical concern, not something proven to happen often, so please don't worry. Keep taking both as prescribed, and let your care team know if you feel fainting, dizziness, or a fluttering heartbeat. They can watch this closely and keep you safe.
Effect: Additive QT-interval prolongation with combined relugolix and formoterol.
- Mechanism: Pharmacodynamic (additive), not metabolic. Androgen deprivation from GnRH antagonists can prolong QT; beta-agonists like formoterol contribute via their own QT effect and potential hypokalemia.
- Direction: Increased torsadogenic risk (neither drug is a prodrug; no PK interaction).
- Evidence: Theoretical. Severity: major. Onset: unspecified.
- Management: Assess baseline risk (congenital long QT, CHF, electrolyte disturbance). Avoid combination when feasible; if required, correct and maintain K+/Mg2+, avoid other hypokalemia-inducing agents, and 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 or antagonists can lengthen the QT interval. In patients with 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 benefits of androgen deprivation therapy such as relugolix are greater than the possible risks1. Whenever 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 abnormalities, and think about periodic monitoring of ECGs and electrolytes1.
Why it happens (mechanism)
Additive QT interval prolongation
How to manage this interaction
Both drugs can nudge your heart rhythm in the same direction, so your care team's goal is to keep that in check. Here is what they typically do:
- Weigh whether you have added risk factors (personal or family history of long QT, heart failure, or electrolyte problems).
- Keep potassium and magnesium in a healthy range, since low levels raise the risk.
- Consider occasional ECG and blood tests to monitor you.
What you can do: keep taking both exactly as prescribed, and ask your pharmacist or doctor before adding any new medicine. Report fainting, palpitations, or dizziness right away. Do not stop either drug on your own.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) A study assessing male patients on androgen deprivation therapy (ADT) using individual case safety reports from VigiBase, the international pharmacovigilance database, 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 concurrent use of other agents known to elevate 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 classified as ADTs comprised abiraterone, gonadotropin-releasing hormone agonists and antagonists, nonsteroidal androgen receptor inhibitors approved for prostate cancer, and 5-alpha-reductase inhibitors approved 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 roughly 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 Formoterol together?
Relugolix and formoterol can each prolong the QT interval, and together the effect may add up, so your care team may keep your electrolytes in range and monitor your ECG. Keep taking both as prescribed and report any fainting or palpitations. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Relugolix and Formoterol 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 Formoterol interaction managed?
Both drugs can nudge your heart rhythm in the same direction, so your care team's goal is to keep that in check. Here is what they typically do: Weigh whether you have added risk factors (personal or family history of long QT, heart failure, or electrolyte problems). Keep potassium and magnesium in a healthy range, since low levels raise the risk. Consider occasional ECG and blood tests to monitor… 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 Formoterol 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 Formoterol
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