Relugolix and Isavuconazonium Sulfate: 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
Isavuconazonium Sulfate
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.
Here's what's going on. Relugolix (Orgovyx) is normally pumped out of your body by a kind of cellular 'gatekeeper' called P-gp. Isavuconazonium (Cresemba), the antifungal, can slow that gatekeeper down. When that happens, more relugolix stays in your body, so its levels go up. That can mean a higher chance of side effects like hot flashes, tiredness, or other relugolix-related reactions.
The good news is this is very manageable. Your care team may space the two medicines apart, watch you more closely, or adjust your plan. Please don't stop or change anything on your own, just let your pharmacist or doctor know you take both so they can guide you safely.
Mechanism: Isavuconazonium (isavuconazole) inhibits P-gp-mediated efflux of relugolix, a P-gp substrate. Neither is a prodrug in a way that reverses direction here; the net effect is increased relugolix exposure and greater risk of relugolix-associated adverse effects.
- Magnitude: A study with erythromycin (P-gp inhibitor) raised relugolix AUC 3.5-fold and Cmax 2.9-fold; expect a comparable-order effect.
- Evidence: Probable. Onset: unspecified.
- Management: Avoid concomitant use if possible. If unavoidable, give relugolix (or relugolix/estradiol/norethindrone) first, separate by at least 6 hours, and monitor closely. Relugolix may be interrupted up to 2 weeks for a short P-gp inhibitor course; if held >7 days, restart with 360 mg loading dose then 120 mg daily.
What happens
Increased relugolix exposure
Interaction Deep Dive
Do not use relugolix (a P-gp substrate) together with P-gp inhibitors, since doing so can raise relugolix exposure and thereby heighten the chance of adverse reactions linked to relugolix. When such coadministration cannot be avoided, give relugolix or relugolix/estradiol/norethindrone acetate first, space the doses by a minimum of 6 hours, and increase the frequency of monitoring for adverse reactions 12. Relugolix therapy may be paused for as long as 2 weeks to allow a brief course of treatment with certain P-gp inhibitors. Relugolix should be resumed once the P-gp inhibitor has been stopped. When relugolix has been interrupted for more than 7 days, it should be restarted using a loading dose of 360 mg on day one, followed by 120 mg once daily thereafter. A drug interaction study showed that giving relugolix (P-gp substrate) alongside erythromycin (P-gp inhibitor) raised relugolix AUC by 3.5-fold and Cmax by 2.9-fold 1.
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 two together when possible, or choose an alternative.
- If both are needed, take the relugolix dose first and separate it from the antifungal by at least 6 hours.
- Watch you more closely for relugolix side effects.
- For a short antifungal course, your team may briefly pause relugolix and restart it afterward (a loading dose may be used if the pause is longer than a week).
What you should do: Keep taking both exactly as prescribed unless your prescriber tells you otherwise, and let your pharmacist or doctor know you take both so they can tailor the timing and monitoring for you.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In a study examining drug interactions, giving relugolix (a P-gp substrate) together with erythromycin (a P-gp inhibitor) raised the AUC and Cmax of relugolix by 3.5-fold and 2.9-fold, respectively 1.
Common questions
Can I take Relugolix and Isavuconazonium Sulfate together?
Cresemba can raise relugolix levels and side effects by blocking a transporter that clears it; your care team will usually avoid the combination or manage it with spacing, monitoring, or a brief relugolix pause. Don't change your medicines on your own, talk with your pharmacist or doctor. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Relugolix and Isavuconazonium Sulfate 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 Isavuconazonium Sulfate interaction managed?
What your care team may do: Try to avoid using these two together when possible, or choose an alternative. If both are needed, take the relugolix dose first and separate it from the antifungal by at least 6 hours. Watch you more closely for relugolix side effects. For a short antifungal course, your team may briefly pause relugolix and restart it afterward (a loading dose may be used if the pause… 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 Isavuconazonium Sulfate 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
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