Relugolix and Sparfloxacin: 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
Sparfloxacin
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.
Both relugolix (Orgovyx) and sparfloxacin can affect the electrical rhythm of your heart in a similar way. Doctors call this QT prolongation, which is a slight change in how the heart resets between beats. When two drugs that do this are taken together, the effect can add up and raise the risk of a dangerous irregular heartbeat.
Because of this, using these two together is generally not recommended. The good news is this is easy to manage. Your care team can choose a different antibiotic that does not carry this risk. Please talk with your pharmacist or doctor before taking both, and never stop a prescribed medicine on your own.
Effect: Additive QT interval prolongation with increased risk of ventricular arrhythmias (including torsades de pointes).
Mechanism: Both agents independently prolong the QT interval; combined use produces additive PD effects on cardiac repolarization. Neither is a prodrug; this is a pharmacodynamic, not metabolic, interaction.
- Direction: Increased combined QT effect.
- Severity: Contraindicated per labeling.
- Evidence: Theoretical.
- Onset: Unspecified.
Management: Avoid concomitant use. Select a non-QT-prolonging antibiotic alternative. If unavoidable, ECG and electrolyte (K+, Mg2+) monitoring would be warranted, though avoidance is preferred given the contraindicated status.
What happens
An increased risk of QT interval prolongation
Interaction Deep Dive
Combining sparfloxacin with agents known to prolong the QT interval is contraindicated, since giving them together can heighten the likelihood of QT prolongation and serious ventricular arrhythmias1.
Why it happens (mechanism)
Additive QT interval prolongation
How to manage this interaction
Because both drugs can affect heart rhythm in the same direction, this combination is generally avoided.
- Keep taking your prescribed medicines and do not stop either one on your own.
- Let your pharmacist or prescriber know you take relugolix before starting any new antibiotic. Your team can usually choose a different antibiotic that does not affect heart rhythm.
- If both must be used, your team may monitor you more closely, including heart tracings (ECG) and blood minerals like potassium and magnesium.
Tell your doctor right away if you feel fainting, palpitations, or a fast or irregular heartbeat.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Relugolix and Sparfloxacin together?
Combining relugolix and sparfloxacin can add up to raise the risk of a dangerous heart rhythm, so this pairing is best avoided. Ask your pharmacist or doctor about a safer antibiotic choice. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Relugolix and Sparfloxacin interaction?
It is rated contraindicated. These should generally not be used together.
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 Sparfloxacin interaction managed?
Because both drugs can affect heart rhythm in the same direction, this combination is generally avoided. Keep taking your prescribed medicines and do not stop either one on your own. Let your pharmacist or prescriber know you take relugolix before starting any new antibiotic. Your team can usually choose a different antibiotic that does not affect heart rhythm. If both must be used, your team may… 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 Sparfloxacin 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 (1)
- Product Information: ZAGAM(R) oral tablets, sparfloxacin oral tablets. Bertek Pharmaceuticals,Inc. Collegeville, PA, 2003.
Keep reading about Relugolix
Keep reading about Sparfloxacin
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