What the FDA labels say about taking them together
Pyrimethamine and sulfamethoxazole/trimethoprim
Sulfamethoxazole/trimethoprim's FDA label of December 30, 2024 names pyrimethamine in its drug interactions section; the pyrimethamine label PlainMeds reads does not name sulfamethoxazole/trimethoprim. The sulfamethoxazole/trimethoprim label: “Avoid concurrent use; Comments: Occasional reports suggest that patients receiving pyrimethamine as malaria prophylaxis in doses exceeding 25 mg weekly may develop megaloblastic anemia if BACTRIM is prescribed.”
Check it at the source: the pyrimethamine FDA label on DailyMed (effective December 7, 2023, TILDE Sciences LLC); the sulfamethoxazole/trimethoprim FDA label on DailyMed (effective December 30, 2024, Sun Pharmaceutical Industries, Inc).
What does the pyrimethamine label say about sulfamethoxazole/trimethoprim?
Pyrimethamine's label (effective December 7, 2023) does not name sulfamethoxazole/trimethoprim in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Daraprim), TILDE Sciences LLC, effective December 7, 2023 (SPL set f634f34b-0952-4dd3-9da3-f84b6ab823de), via openFDA; the full label on DailyMed
What does the sulfamethoxazole/trimethoprim label say about pyrimethamine?
Sulfamethoxazole/trimethoprim label, drug interactionsDrug (s): Pyrimethamine; Recommendation: Avoid concurrent use; Comments: Occasional reports suggest that patients receiving pyrimethamine as malaria prophylaxis in doses exceeding 25 mg weekly may develop megaloblastic anemia if BACTRIM is prescribed.
Sulfatrim label (Preferred Pharmaceuticals, Inc., September 2, 2026), drug interactionsOccasional reports suggest that patients receiving pyrimethamine as malaria prophylaxis in doses exceeding 25 mg weekly may develop megaloblastic anemia if sulfamethoxazole and trimethoprim is prescribed.
Source: FDA drug label (Sulfatrim, NDA018615), Preferred Pharmaceuticals, Inc., effective September 2, 2026 (SPL set cd4932ce-0856-4e99-8baf-70afce1d7ffd), via openFDA
Source: FDA drug label (Bactrim), Sun Pharmaceutical Industries, Inc, effective December 30, 2024 (SPL set f59d0c04-9c66-4d53-a0e1-cb55570deb62), 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
| Pyrimethamine | Sulfamethoxazole/trimethoprim | |
|---|---|---|
| Labeled for | n/a | Bacterial infections, Urinary tract infections, Diarrhea |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $137.01 per tablet 25 mg tablet | $0.0448 per tablet Sulfamethoxazole-tmp ds tablet |
| 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