What the FDA labels say about taking them together
Gentamicin and polymyxin b
Polymyxin b's FDA label of May 9, 2025 names gentamicin in its boxed warning section; the gentamicin label PlainMeds reads does not name polymyxin b.
Check it at the source: the gentamicin FDA label on DailyMed (effective July 22, 2024, Bausch & Lomb Incorporated); the polymyxin b FDA label on DailyMed (effective May 9, 2025, Gland Pharma Limited).
What does the gentamicin label say about polymyxin b?
Gentamicin's label (effective July 22, 2024) does 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 (Gentamicin Sulfate), Bausch & Lomb Incorporated, effective July 22, 2024 (SPL set 41d01350-5c4b-42fc-be5f-986ceec02bd3), via openFDA; the full label on DailyMed
What does the polymyxin b label say about gentamicin?
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
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
| Gentamicin | Polymyxin b | |
|---|---|---|
| Labeled for | Bacterial infections | Bacterial infections, Urinary tract infections |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $1.30 per mL 80 mg/2 mL vial | 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