Sertraline and Thioridazine: 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
Sertraline
No brand names on recordThioridazine
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.
These two medicines are not meant to be taken together. Sertraline is an antidepressant, and thioridazine is an older medicine used for certain mental health conditions. Both can affect the electrical timing of your heartbeat, something doctors call the QT interval. When taken together, that effect can add up and, in rare cases, lead to a dangerous irregular heartbeat.
Because of this, thioridazine's label lists this combination as one to avoid. The good news is that your care team has many safe options. Do not stop either medicine on your own, but please reach out to your pharmacist or doctor so they can review your medicines and find a safer plan for you.
Contraindicated combination. Both agents independently prolong the QT interval, so concurrent use produces additive QTc prolongation and raises the risk of torsades de pointes and serious ventricular arrhythmias.
- Mechanism: additive pharmacodynamic QT prolongation (both delay cardiac repolarization).
- Direction: increased combined QT effect; neither drug is a prodrug.
- Evidence: theoretical, but severity is rated contraindicated per thioridazine labeling.
- Management: avoid coadministration. If a QT-prolonging antidepressant is needed, select an alternative. If unavoidable, ECG and electrolyte (K+, Mg2+) monitoring is warranted, though avoidance is preferred.
What happens
An increased risk of QT interval prolongation
Interaction Deep Dive
Giving thioridazine together with agents that prolong the QT interval is contraindicated, since combining them can heighten the likelihood of QT prolongation and dangerous ventricular arrhythmias1.
Why it happens (mechanism)
Additive QT interval prolongation
How to manage this interaction
This pairing is flagged as one to avoid, so your care team will usually choose a different medicine rather than combine these two.
- Keep taking both medicines as prescribed until you have spoken with your prescriber or pharmacist. Do not stop on your own.
- Tell your care team about this combination as soon as possible so they can review it.
- Your team may switch one medicine to a safer alternative, or if both are truly needed, monitor your heart rhythm (ECG) and blood electrolytes more closely.
- Report symptoms like fainting, dizziness, palpitations, or a racing or irregular heartbeat right away.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Sertraline and Thioridazine together?
Sertraline and thioridazine both prolong the QT interval, and combining them is contraindicated because of the added risk of dangerous heart rhythms. Contact your pharmacist or doctor so they can choose a safer option, and do not stop either drug on your own. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Sertraline and Thioridazine 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 Sertraline and Thioridazine interaction managed?
This pairing is flagged as one to avoid, so your care team will usually choose a different medicine rather than combine these two. Keep taking both medicines as prescribed until you have spoken with your prescriber or pharmacist. Do not stop on your own. Tell your care team about this combination as soon as possible so they can review it. Your team may switch one medicine to a safer alternative, o… 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.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Sertraline or Thioridazine 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 Sertraline
Keep reading about Thioridazine
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist