Thioridazine 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
Thioridazine
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.
These two medicines can each affect your heart's electrical timing, something doctors call the QT interval. Thioridazine is an older antipsychotic that is well known for this, and relugolix can add to that effect. When both are taken together, the timing can stretch out too far, which in rare cases can trigger a dangerous, irregular heartbeat.
Because of this, the two are generally not used together. The good news is your care team can manage this safely. Please don't stop either medicine on your own. Instead, reach out to your pharmacist or doctor so they can review your medicines and pick the safest plan for you.
Effect: Additive QT interval prolongation, increasing the risk of serious ventricular arrhythmias (including torsades de pointes).
- Mechanism: Pharmacodynamic additive effect; both agents can prolong cardiac repolarization. Not a prodrug or CYP-based interaction.
- Direction/magnitude: Additive QTc prolongation; magnitude not quantified.
- Evidence: Theoretical, but severity on file is contraindicated given thioridazine's known pronounced QT liability.
- Management: Avoid concomitant use. If unavoidable, an alternative agent is preferred; otherwise ECG and electrolyte monitoring (K+, Mg2+) with dose individualization by the care team.
What happens
An increased risk of QT interval prolongation
Interaction Deep Dive
Using thioridazine together with agents known to prolong the QT interval is contraindicated, since giving them together can heighten the likelihood of QT prolongation along with serious ventricular arrhythmias1.
Why it happens (mechanism)
Additive QT interval prolongation
How to manage this interaction
This combination is generally avoided because both drugs can lengthen the heart's QT interval.
- Keep taking both medicines as prescribed until you speak with your care team. Do not stop either one on your own.
- Your team may choose an alternative medicine, or if both are truly needed, they may monitor you more closely with ECGs and blood tests for electrolytes like potassium and magnesium.
- Tell your pharmacist or prescriber about all your medicines so they can tailor the safest plan for you.
- Seek urgent care if you feel fainting, dizziness, palpitations, or an irregular heartbeat.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Thioridazine and Relugolix together?
Thioridazine and relugolix together can add up to a dangerous heart rhythm risk and are generally not used at the same time; talk with your pharmacist or doctor before changing anything. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Thioridazine and Relugolix 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 Thioridazine and Relugolix interaction managed?
This combination is generally avoided because both drugs can lengthen the heart's QT interval. Keep taking both medicines as prescribed until you speak with your care team. Do not stop either one on your own. Your team may choose an alternative medicine, or if both are truly needed, they may monitor you more closely with ECGs and blood tests for electrolytes like potassium and magnesium. Tell your… 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 Thioridazine 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 (1)
- Product Information: thioridazine HCl oral tablets, thioridazine HCl oral tablets. Sun Pharmaceutical Industries, Inc. (per DailyMed), Cranbury, NJ, 2014.
Keep reading about Thioridazine
Keep reading about Relugolix
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