What the FDA labels say about taking them together
Clozapine and procainamide
Clozapine's FDA label of June 6, 2025 names procainamide in its drug interactions section; the procainamide label PlainMeds reads does not name clozapine. The clozapine label: “Drugs that cause QT prolongation include: specific antipsychotics, specific antibiotics, Class 1A antiarrhythmics or Class III antiarrhythmics, and others.”
Check it at the source: the clozapine FDA label on DailyMed (effective June 6, 2025, HLS Therapeutics (USA), Inc.); the procainamide FDA label on DailyMed (effective February 17, 2025, Caplin Steriles Limited).
What does the clozapine label say about procainamide?
Clozapine label, drug interactionsDrugs 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 )].
Source: FDA drug label (Clozaril), NDA019758 (Heritage Life), as published by HLS Therapeutics (USA), Inc., effective June 6, 2025 (SPL set 90876802-0e3a-44c9-9ff7-1754dfbe736a), via openFDA; the full label on DailyMed
What does the procainamide label say about clozapine?
Procainamide's label (effective February 17, 2025) does not name clozapine in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Procainamide Hydrochloride), Caplin Steriles Limited, effective February 17, 2025 (SPL set fcaa5e9a-3c8a-4796-aa87-626268b6cf60), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Clozapine | Procainamide | |
|---|---|---|
| Labeled for | Schizophrenia | n/a |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.610 per tablet 100 mg tablet | n/a |
| Shortage now | No current entry | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once