What the FDA labels say about taking them together
Polymyxin b and tobramycin
Polymyxin b's FDA label of May 9, 2025 names tobramycin in its boxed warning section; the tobramycin labels PlainMeds reads (4) do not name polymyxin b.
Check it at the source: the polymyxin b FDA label on DailyMed (effective May 9, 2025, Gland Pharma Limited); the tobramycin FDA label on DailyMed (effective November 1, 2023, Bausch & Lomb Incorporated).
What does the polymyxin b label say about tobramycin?
Polymyxin b label, boxed warningTHE CONCURRENT OR SEQUENTIAL USE OF OTHER NEUROTOXIC AND/OR NEPHROTOXIC DRUGS WITH POLYMYXIN B SULFATE, PARTICULARLY BACITRACIN, STREPTOMYCIN, NEOMYCIN, KANAMYCIN, GENTAMICIN, TOBRAMYCIN, AMIKACIN, CEPHALORIDINE, PAROMOMYCIN, VIOMYCIN, AND COLISTIN SHOULD BE AVOIDED.
Source: FDA drug label (POLYMYXIN B), Gland Pharma Limited, effective May 9, 2025 (SPL set dc74dee2-1d0b-4fab-a29b-1755fdb5da75), via openFDA; the full label on DailyMed
What does the tobramycin label say about polymyxin b?
Tobramycin's label (effective November 1, 2023) and its 3 other brand-application labels do not name polymyxin b in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Tobramycin), Bausch & Lomb Incorporated, effective November 1, 2023 (SPL set a5693ec9-d2f7-4d45-90b0-a113c54840d7), 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
| Polymyxin b | Tobramycin | |
|---|---|---|
| Labeled for | Bacterial infections, Urinary tract infections | Bacterial infections, Urinary tract infections |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | n/a | $1.08 per mL 300 mg/5 mL ampule |
| Shortage now | No current entry | A presentation being discontinued |
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