Relugolix and Quinine: 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
Quinine
No brand names on recordRelugolix
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.
Let's talk about taking quinine and relugolix (Orgovyx) together. Quinine can block a 'pump' in your body called P-gp that normally helps push relugolix out. When that pump is slowed, more relugolix can build up, which may raise your chance of side effects.
On top of that, both of these drugs can affect your heart's rhythm by lengthening something called the QT interval. Together that effect can add up, which is why doctors watch this combination closely. The good news is that this is theoretical and very manageable. Please don't stop either medicine on your own. Talk with your pharmacist or doctor so they can time your doses and monitor your heart.
Effect: Quinine may increase relugolix exposure and add to QT prolongation risk.
- Mechanism: Quinine inhibits P-gp, reducing efflux of the P-gp substrate relugolix, raising AUC/Cmax; additive QTc prolongation (both agents prolong QT).
- Direction: Increased relugolix effect and cardiac risk. Neither is a prodrug here.
- Evidence/Onset: Theoretical; onset unspecified. Severity major.
- Management: Avoid concomitant use. If unavoidable, give relugolix first, separate by at least 6 hours, monitor for adverse reactions. Relugolix may be interrupted up to 2 weeks for short P-gp inhibitor courses; if held greater than 7 days, restart with 360 mg loading dose then 120 mg daily. Correct electrolytes and consider periodic ECG/electrolyte monitoring.
What happens
Increased relugolix exposure and an increased risk of QT interval prolongation
Interaction Deep Dive
Do not use relugolix (a P-gp substrate) together with P-gp inhibitors, since this combination can raise relugolix exposure and thereby heighten the likelihood of adverse reactions. When coadministration cannot be avoided, give the relugolix-containing medication 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 up to 2 weeks to allow a brief course of a P-gp inhibitor, with relugolix resumed once the P-gp inhibitor has been stopped. Should relugolix be interrupted for more than 7 days, reintroduce it using a loading dose of 360 mg on day one, followed by 120 mg once daily thereafter1. When relugolix is combined with drugs that prolong the QT interval, additive effects on the QT interval may result. Weigh whether the benefits of androgen deprivation therapy such as relugolix justify the potential risks in patients who have congenital long QT syndrome, congestive heart failure, or recurrent electrolyte abnormalities, as well as in those receiving medications recognized to prolong the QT interval. Electrolyte disturbances should be corrected, and periodic monitoring of ECGs and electrolytes should be considered1.
Why it happens (mechanism)
Inhibition of P-gp-mediated efflux transport of relugolix; additive QT interval prolongation
How to manage this interaction
Your care team can handle this combination. Keep taking both medicines exactly as prescribed unless your prescriber tells you otherwise.
- Your team may prefer to avoid using them together when possible.
- If both are needed, they may have you take your relugolix first and separate the doses by at least 6 hours, and watch you more closely for side effects.
- Because both can affect heart rhythm, your team may check ECGs and blood electrolytes and correct any low levels.
- Tell your doctor if you have heart problems, a history of long QT, or take other heart-rhythm drugs.
Report any fainting, palpitations, or dizziness right away.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) When relugolix (a P-gp substrate) was given together with erythromycin (an inhibitor of P-gp and CYP3A), the AUC and Cmax of relugolix rose by 3.5-fold and 2.9-fold, respectively 1.
Common questions
Can I take Relugolix and Quinine together?
Quinine can raise relugolix levels and both can affect heart rhythm, so this combination is best avoided; if you take both, your care team will separate the doses and monitor your heart and electrolytes. 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 Quinine 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 Quinine interaction managed?
Your care team can handle this combination. Keep taking both medicines exactly as prescribed unless your prescriber tells you otherwise. Your team may prefer to avoid using them together when possible. If both are needed, they may have you take your relugolix first and separate the doses by at least 6 hours, and watch you more closely for side effects. Because both can affect heart rhythm, your te… 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 Quinine 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 Quinine
Keep reading about Relugolix
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