What the FDA labels say about taking them together
Fosfomycin and tromethamine
Fosfomycin's FDA label of April 9, 2026 names tromethamine in its contraindications section; the tromethamine label PlainMeds reads does not name fosfomycin. The fosfomycin label: “CONTRAINDICATIONS Fosfomycin tromethamine granules for oral solution is contraindicated in patients with known hypersensitivity to the drug.”
Check it at the source: the fosfomycin FDA label on DailyMed (effective April 9, 2026, Aucta Pharmaceuticals, Inc.); the tromethamine FDA label on DailyMed (effective May 27, 2026, Hospira, Inc.).
What does the fosfomycin label say about tromethamine?
Fosfomycin label, contraindicationsCONTRAINDICATIONS Fosfomycin tromethamine granules for oral solution is contraindicated in patients with known hypersensitivity to the drug.
Fosfomycin label, drug interactionsDrug Interactions Metoclopramide: When coadministered with fosfomycin tromethamine, metoclopramide, a drug which increases gastrointestinal motility, lowers the serum concentration and urinary excretion of fosfomycin.
Fosfomycin label, warningsWARNINGS Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including fosfomycin tromethamine granules for oral solution, and may range in severity from mild diarrhea to fatal colitis.
Source: FDA drug label (Fosfomycin Tromethamine), Aucta Pharmaceuticals, Inc., effective April 9, 2026 (SPL set 4f206750-8126-99a3-e063-6294a90ade4c), via openFDA; the full label on DailyMed
What does the tromethamine label say about fosfomycin?
Tromethamine's label (effective May 27, 2026) does not name fosfomycin in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (THAM), Hospira, Inc., effective May 27, 2026 (SPL set 4af52118-c12b-4ad5-30bb-959848357e8a), 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
| Fosfomycin | Tromethamine | |
|---|---|---|
| Labeled for | Urinary tract infections | n/a |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $26.22 per unit 3 g sachet | 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