Polymyxin B / bacitracin
Anti-infective · Rx
Trade namesPolysporin ophthalmic ointment
Drug classAntibiotic, combination (ointment)
StrengthPolymyxin B 10,000 U + bacitracin 500 U per g
AvailabilityRx
Mechanism of actionPolymyxin B (Gram-negative membrane) plus bacitracin (Gram-positive cell-wall synthesis inhibition).
Indication / reason for useBacterial conjunctivitis and blepharitis; overnight antibacterial lubrication.
Usual adult dosingRibbon into the lower fornix every 3-4 h (acute) or at bedtime.
PreservativePreservative-free ointment base , a preservative-free option exists
Contact lensesNo lens wear during infection.
Common / important adverse effectsBlur, contact dermatitis / hypersensitivity (bacitracin, neomycin cross-reactivity).
Contraindications & cautionsHypersensitivity.
Pregnancy / lactationLow risk.
Practice notesNeomycin-containing versions (Neosporin) cause more contact allergy, prefer the neomycin-free combination.
Chair-side reference only. Dosing, contraindications and pregnancy guidance here are not exhaustive. Confirm against the current prescribing information and the patient’s full history before prescribing or advising.