Cimetidine and Relugolix: 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
Cimetidine
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.
Cimetidine (Tagamet) can raise the level of relugolix (Orgovyx) in your body. Cimetidine blocks a kind of 'pump' in your gut that normally moves some relugolix back out, so more of it gets absorbed. When relugolix builds up, you may be more likely to notice its side effects, such as hot flashes, tiredness, or joint aches.
The good news is that this is very manageable. Please don't stop or change either medicine on your own. Instead, let your pharmacist or doctor know you take both, and they can adjust timing, watch you a little more closely, or suggest another option. A quick conversation is all it takes to keep you safe.
Effect: Increased relugolix exposure via inhibition of intestinal P-gp-mediated efflux (relugolix is a P-gp substrate; cimetidine is a P-gp inhibitor). Neither is a prodrug, so this raises active relugolix levels.
- Direction/magnitude: Increased AUC/Cmax; a study with erythromycin (P-gp inhibitor) showed 3.5-fold AUC and 2.9-fold Cmax increases.
- Severity/evidence: Major; probable. Onset unspecified.
- Management: Avoid coadministration if possible. If unavoidable, give relugolix first, separate by at least 6 hours, and monitor more frequently for adverse reactions. For short P-gp inhibitor courses, relugolix may be interrupted up to 2 weeks; if interrupted more than 7 days, restart with a 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, because doing so can raise relugolix exposure and thereby heighten the likelihood of relugolix-related adverse reactions. When such 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, with relugolix resumed once the P-gp inhibitor has been stopped. Should relugolix be interrupted for more than 7 days, restart it using a loading dose of 360 mg on day one, then continue at 120 mg once daily. In a drug interaction study, giving relugolix (P-gp substrate) alongside erythromycin (P-gp inhibitor) raised relugolix AUC and Cmax 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 cimetidine and relugolix together when possible, or choose an alternative for one of them.
- If both are needed, take relugolix first and separate the two doses by at least 6 hours.
- Monitor you more closely for relugolix side effects.
- For a short course of cimetidine, relugolix may be paused and then resumed, with dosing individualized by your team.
What you should do: Keep taking both exactly as prescribed unless told otherwise, and tell your pharmacist or prescriber that you take both so they can tailor timing, monitoring, or your dose.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In a study evaluating 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 Cimetidine and Relugolix together?
Cimetidine can significantly raise relugolix levels and its side effects, so tell your pharmacist or doctor you take both; they can separate the doses, monitor you, or adjust your plan. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Cimetidine and Relugolix 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 Cimetidine and Relugolix interaction managed?
What your care team may do: Try to avoid using cimetidine and relugolix together when possible, or choose an alternative for one of them. If both are needed, take relugolix first and separate the two doses by at least 6 hours. Monitor you more closely for relugolix side effects. For a short course of cimetidine, relugolix may be paused and then resumed, with dosing individualized by your team. Wha… 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 Cimetidine or Relugolix 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 Cimetidine
Keep reading about Relugolix
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