Thioridazine and Clozapine Interaction
Drug interaction information between Thioridazine and Clozapine.
Thioridazine and Clozapine have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Thioridazine and Clozapine. This page displays the available source-record category and label text. The category is not an individual risk estimate or medication-combination direction.
How They Interact
Both drugs can cause the heart's electrical cycle to take longer than normal to reset. This combination makes it more likely that you will experience a life-threatening heart rhythm.
FDA Label Information
Drugs that cause QT prolongation include: specific antipsychotics (e.g., ziprasidone, iloperidone, chlorpromazine, thioridazine, mesoridazine, droperidol, and pimozide), specific antibiotics (e.g., erythromycin, gatifloxacin, moxifloxacin, sparfloxacin), Class 1A antiarrhythmics (e.g., quinidine, procainamide) or Class III antiarrhythmics (e.g., amiodarone, sotalol), and others (e.g., pentamidine, levomethadyl acetate, methadone, halofantrine, mefloquine, dolasetron mesylate, probucol or tacrolimus) [see Warnings and Precautions (5.9) ] .
Thioridazine Also Interacts With
- Fluoxetine major
- Paroxetine major
- Rolapitant major
- Abiraterone moderate
- Darifenacin moderate
Clozapine Also Interacts With
- Cyclobenzaprine moderate
- Diphenhydramine moderate
- Fluoxetine moderate
- Sertraline minor
- Escitalopram minor
Frequently Asked Questions
What SPL severity band is on file for Thioridazine + Clozapine?
Compiled FDA labeling labels this pair minor. That is a source-record field, not an individual medication-combination decision.
Which drug in this pair has the larger labeled-interaction portfolio?
Clozapine has 42 labeled pairs on file vs Thioridazine's 17. In the minor band specifically: Thioridazine has 11 (also Propranolol, Pindolol, Bupropion, Carbamazepine); Clozapine has 39 (also Sertraline, Escitalopram, Bupropion, Duloxetine).
What mechanism field is on file for Thioridazine and Clozapine?
Both drugs can cause the heart's electrical cycle to take longer than normal to reset. This combination makes it more likely that you will experience a life-threatening heart rhythm.
Thioridazine carries more major-labeled pairs than Clozapine
SPL source-record counts only. This page's band is minor · classes on file: Thioridazine (Typical Antipsychotic (Phenothiazine)); Clozapine (Atypical Antipsychotic).
Thioridazine has 3 major-labeled pairs vs Clozapine's 0. This page itself is in the minor band, not the major band.
3 major · 3 moderate · 11 minor · 17 total
- Other minor peers for Thioridazine
- Propranolol
- Pindolol
- Bupropion
- Carbamazepine
0 major · 3 moderate · 39 minor · 42 total
- Other minor peers for Clozapine
- Sertraline
- Escitalopram
- Bupropion
- Duloxetine
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. This registry does not provide individual medication-combination directions.
Read our methodology - how this data is sourced, computed, and verified.