Relugolix and Osimertinib: 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
Osimertinib
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.
You've been prescribed osimertinib (Tagrisso) for cancer and relugolix (Orgovyx) for prostate cancer. Osimertinib can block a transporter called P-gp that normally helps push relugolix out of your body. When that pathway is slowed, more relugolix can build up, which may raise the chance of side effects.
On top of that, both medicines can affect your heart's rhythm by lengthening something called the QT interval. Together they may add up. The good news is your care team can manage this by watching you more closely, checking your heart with an ECG, and keeping your electrolytes (like potassium) in a healthy range. Never change either medicine on your own, talk with your doctor or pharmacist first.
Effect: Osimertinib may inhibit P-gp-mediated efflux of relugolix (a P-gp substrate), increasing relugolix exposure and adverse-reaction risk. Both agents can prolong the QT interval, producing additive PD effects.
- Direction: Increased relugolix exposure; additive QT prolongation.
- Evidence: Theoretical.
- Onset: Unspecified.
- Management: Avoid concurrent use if possible. If unavoidable, give relugolix first and separate dosing by at least 6 hours; monitor more frequently. Relugolix may be interrupted up to 2 weeks for short P-gp inhibitor courses (if held >7 days, restart with 360 mg loading dose, then 120 mg daily). Correct electrolytes; consider periodic ECG and electrolyte monitoring, especially with long QT syndrome, CHF, or electrolyte abnormalities.
What happens
Increased relugolix exposure and an increased risk of QT interval prolongation
Interaction Deep Dive
Do not combine relugolix (a P-gp substrate) with P-gp inhibitors, since doing so can raise relugolix exposure and thereby heighten the likelihood of adverse reactions. When coadministration cannot be avoided, give the relugolix-containing product first, allow a gap of at least 6 hours between doses, and increase the frequency of monitoring for adverse reactions12. Relugolix therapy may be paused for as long as 2 weeks to allow a brief course of a P-gp inhibitor. Once the P-gp inhibitor has been stopped, relugolix can be resumed. Should relugolix be interrupted for more than 7 days, reinitiate it using a 360 mg loading dose on day one, followed by 120 mg once daily thereafter1. Giving relugolix together with agents that prolong the QT interval can produce additive QT effects. In patients with congenital long QT syndrome, congestive heart failure, or recurrent electrolyte disturbances, as well as those receiving medications known to prolong the QT interval, weigh whether the benefits of androgen deprivation therapy such as relugolix outweigh the possible risks. Correct any electrolyte abnormalities and consider intermittent monitoring of ECGs and electrolytes1.
Why it happens (mechanism)
Inhibition of P-gp-mediated efflux transport of relugolix; additive QT interval prolongation
How to manage this interaction
Keep taking both exactly as prescribed unless your care team tells you otherwise. Your team may take steps such as:
- Separating your doses (typically taking relugolix first, then spacing by at least 6 hours) if both must be used together.
- Watching more closely for side effects.
- Checking your heart rhythm with periodic ECGs and keeping electrolytes like potassium and magnesium in range.
- In some cases, briefly pausing relugolix during a short course of the other drug, then restarting under their direction.
Tell your pharmacist or doctor if you have a history of heart rhythm problems, heart failure, or fainting. Any dose changes should be individualized by your care team.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) Giving relugolix (a P-gp substrate) together with erythromycin (a P-gp and CYP3A inhibitor) raised the AUC of relugolix by 3.5-fold and the Cmax by 2.9-fold 1.
Common questions
Can I take Relugolix and Osimertinib together?
Combining osimertinib and relugolix can raise relugolix levels and add to QT prolongation, so your care team may separate doses, monitor ECGs and electrolytes, and watch for side effects. Do not change either drug on your own. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Relugolix and Osimertinib 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 Osimertinib interaction managed?
Keep taking both exactly as prescribed unless your care team tells you otherwise. Your team may take steps such as: Separating your doses (typically taking relugolix first, then spacing by at least 6 hours) if both must be used together. Watching more closely for side effects. Checking your heart rhythm with periodic ECGs and keeping electrolytes like potassium and magnesium in range. In some case… 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 Osimertinib 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 (2)
- Product Information: ORGOVYX oral tablets, relugolix oral tablets. Sumitomo Pharma America, Inc (per FDA), Marlborough, MA, 2025. DailyMed
- Product Information: MYFEMBREE(R) oral tablets, relugolix, estradiol, norethindrone acetate oral tablets. Myovant Sciences Inc (per FDA), Brisbane, CA, 2021. DailyMed
Keep reading about Osimertinib
Keep reading about Relugolix
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