Relugolix and Isavuconazole: 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
Isavuconazole
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.
These two medicines can interact. Relugolix (Orgovyx) is moved out of your body with the help of a transporter called P-gp. Isavuconazole can slow that transporter down. When that happens, more relugolix stays in your body, so you may be more likely to have relugolix side effects like hot flashes, tiredness, or muscle and joint aches.
The good news is this is very manageable. Your care team can space the doses apart, watch you more closely, or adjust your plan. Please do not stop or change either medicine on your own. Just talk with your pharmacist or doctor so they can guide you.
Effect: Increased relugolix exposure via inhibition of P-gp-mediated efflux (relugolix is a P-gp substrate; isavuconazole is a P-gp inhibitor). Neither drug's activation is prodrug-dependent, so this reflects true accumulation and increased adverse-reaction risk.
- Magnitude: Reference P-gp inhibitor (erythromycin) raised relugolix AUC ~3.5-fold and Cmax ~2.9-fold.
- Evidence/onset: Probable; onset unspecified.
- Management: Avoid coadministration. If unavoidable, give relugolix first, separate by at least 6 hours, and monitor adverse reactions more frequently. Relugolix may be interrupted up to 2 weeks for short P-gp inhibitor courses; if held >7 days, restart with a 360 mg loading dose then 120 mg daily.
What happens
Increased relugolix exposure
Interaction Deep Dive
Concurrent administration of relugolix (a P-gp substrate) with P-gp inhibitors should be avoided, since it can raise relugolix exposure and thereby heighten the likelihood of relugolix-related adverse reactions. When coadministration cannot be avoided, give relugolix or relugolix/estradiol/norethindrone acetate 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 accommodate a brief course of certain P-gp inhibitors, resuming relugolix once the P-gp inhibitor has been stopped. Should relugolix be withheld for longer than 7 days, reinitiate it using a 360 mg loading dose on day one and then continue at 120 mg once daily. In a drug interaction study, giving relugolix (P-gp substrate) together with erythromycin (P-gp inhibitor) raised the AUC and Cmax of relugolix by 3.5-fold and 2.9-fold, respectively1.
Why it happens (mechanism)
Inhibition of P-gp-mediated efflux transport of relugolix
How to manage this interaction
What your care team may do:
- Try to avoid using these together when possible.
- If both are needed, take relugolix first and separate the doses by at least 6 hours.
- Watch you more closely for relugolix side effects.
- Sometimes pause relugolix during a short isavuconazole course, then resume it (with a loading dose if it was held more than 7 days) once isavuconazole is stopped.
What you should do: Keep taking both exactly as prescribed unless your prescriber tells you otherwise. Let your pharmacist or doctor know you are on both so they can tailor timing and monitoring for you.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) During a drug interaction study, giving relugolix (a P-gp substrate) together with erythromycin (a P-gp inhibitor) raised the AUC of relugolix by 3.5-fold and its Cmax by 2.9-fold 1.
Common questions
Can I take Relugolix and Isavuconazole together?
Isavuconazole can raise relugolix levels and side effects by blocking its P-gp transport, so your care team will usually avoid the combo or, if needed, dose relugolix first, separate doses by at least 6 hours, and monitor you closely. Do not change either medicine on your own. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Relugolix and Isavuconazole 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 Isavuconazole interaction managed?
What your care team may do: Try to avoid using these together when possible. If both are needed, take relugolix first and separate the doses by at least 6 hours. Watch you more closely for relugolix side effects. Sometimes pause relugolix during a short isavuconazole course, then resume it (with a loading dose if it was held more than 7 days) once isavuconazole is stopped. What you should do: Keep… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Relugolix or Isavuconazole 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 Relugolix
Keep reading about Isavuconazole
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