What the FDA labels say about taking them together
Leucovorin and sulfamethoxazole/trimethoprim
Sulfamethoxazole/trimethoprim's FDA label of December 30, 2024 names leucovorin in its warnings section; the leucovorin labels PlainMeds reads (2) do not name sulfamethoxazole/trimethoprim. The sulfamethoxazole/trimethoprim label: “Risk Associated with Concurrent Use of Leucovorin for Pneumocystis jirovecii Pneumonia Treatment failure and excess mortality were observed when BACTRIM was used concomitantly with leucovorin for the treatment of HIV …”
Check it at the source: the leucovorin FDA label on DailyMed (effective March 19, 2025, Meitheal Pharmaceuticals Inc.); the sulfamethoxazole/trimethoprim FDA label on DailyMed (effective December 30, 2024, Sun Pharmaceutical Industries, Inc).
What does the leucovorin label say about sulfamethoxazole/trimethoprim?
Leucovorin's label (effective March 19, 2025) and its 1 other brand-application label do 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 (leucovorin calcium), Meitheal Pharmaceuticals Inc., effective March 19, 2025 (SPL set 9df20901-6980-4d4e-89ec-40f3c1f91852), via openFDA; the full label on DailyMed
What does the sulfamethoxazole/trimethoprim label say about leucovorin?
Sulfamethoxazole/trimethoprim label, warningsRisk Associated with Concurrent Use of Leucovorin for Pneumocystis jirovecii Pneumonia Treatment failure and excess mortality were observed when BACTRIM was used concomitantly with leucovorin for the treatment of HIV positive patients with P. jirovecii pneumonia in a randomized placebo-controlled trial.
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
| Leucovorin | Sulfamethoxazole/trimethoprim | |
|---|---|---|
| Labeled for | Colorectal cancer | Bacterial infections, Urinary tract infections, Diarrhea |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.330 per tablet 5 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