What the FDA labels say about taking them together
Amantadine and sulfamethoxazole/trimethoprim
Sulfamethoxazole/trimethoprim's FDA label of December 30, 2024 names amantadine in its drug interactions section; the amantadine labels PlainMeds reads (2) do not name sulfamethoxazole/trimethoprim. The sulfamethoxazole/trimethoprim label: “Amantadine Avoid concurrent use In the literature, a single case of toxic delirium has been reported after concomitant intake of BACTRIM and amantadine (an OCT2 substrate).”
Check it at the source: the amantadine FDA label on DailyMed (effective January 30, 2026, Strides Pharma Inc.); the sulfamethoxazole/trimethoprim FDA label on DailyMed (effective December 30, 2024, Sun Pharmaceutical Industries, Inc).
What does the amantadine label say about sulfamethoxazole/trimethoprim?
Amantadine's label (effective January 30, 2026) 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 (Amantadine Hydrochloride), Strides Pharma Inc., effective January 30, 2026 (SPL set e4d8f36f-d668-4728-8dca-b1c22bd9aedb), via openFDA; the full label on DailyMed
What does the sulfamethoxazole/trimethoprim label say about amantadine?
Sulfamethoxazole/trimethoprim label, drug interactionsAmantadine Avoid concurrent use In the literature, a single case of toxic delirium has been reported after concomitant intake of BACTRIM and amantadine (an OCT2 substrate).
Sulfatrim label (Preferred Pharmaceuticals, Inc., September 2, 2026), drug interactionsIn the literature, a single case of toxic delirium has been reported after concomitant intake of sulfamethoxazole/trimethoprim and amantadine.
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
| Amantadine | Sulfamethoxazole/trimethoprim | |
|---|---|---|
| Labeled for | Influenza, Parkinson's disease | Bacterial infections, Urinary tract infections, Diarrhea |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.143 per capsule 100 mg capsule | $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