Polymyxin B
Polymyxin B is a polypeptide antibacterial and endotoxin-binding agent.
Group
Polypeptide antibacterial and endotoxin-binding agent
Mechanism of Action
Disrupts bacterial phospholipid membranes and binds endotoxin.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Bacterial infection | 15000–25000 IU/kg | IV | Every 12 h | Reported dilution: 500000 IU in 300-500 mL 5% dextrose for infusion. |
| Bacterial infection | 30000 IU/kg | IM | Every 24 h | Daily IM amount; reported dissolves 500000 IU in 2 mL suitable diluent. Painful injection. |
| Endotoxemia | 1 mg/kg | IV | Dilute in 10 mL saline and infuse. Milligram dose is polymyxin B base; 1 mg base equals 10000 IU. |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Bacterial infection | 15000–25000 IU/kg | IV | Every 12 h | Reported dilution: 500000 IU in 300-500 mL 5% dextrose for infusion. |
| Bacterial infection | 30000 IU/kg | IM | Every 24 h | Daily IM amount; reported dissolves 500000 IU in 2 mL suitable diluent. Painful injection. |
| Endotoxemia | 1 mg/kg | IV | Dilute in 10 mL saline and infuse. Milligram dose is polymyxin B base; 1 mg base equals 10000 IU. |
Horses
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Endotoxemia | 1000–10000 IU/kg | IV | Every 8 h | Usually 6000 IU/kg. Infuse in 1 L saline over 15 minutes; reported regimen describes five treatments. |
| Endotoxemia | 6000 IU/kg | IV | Every 8 h | Typical regimen; 15-minute infusion, five treatments described. |
Indications
- Resistant susceptible bacterial infections
- Equine endotoxemia
- Topical infection
Contraindications
- Renal disease: avoid or use with particular caution.
Interactions
- Nephrotoxins increase renal risk; neuromuscular blockers and other neurotoxic drugs increase respiratory risk.
- Calcium, magnesium, strong acids/alkalis and anionic detergents can be incompatible.
Adverse effects
- Nephrotoxicity, injection pain, allergy and respiratory depression at high systemic doses.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Polymyxin B 500000 IU vial | Injection | 500000 IU / vial | IV, IM |
| Terramycin oxytetracycline/polymyxin B ophthalmic ointment Sterile ocular ointment contains oxytetracycline HCl 5 mg and polymyxin B sulfate activity 10000 IU per gram; no single-component calculator opt-in. | Other | polymyxin b 10000 IU / g + oxytetracycline hydrochloride 5 mg / g | TOPICAL |
Monitoring and Administration
Maintain renal perfusion and hydration; monitor BUN, creatinine and electrolytes. Use microbiology to justify systemic antibacterial treatment.
Intrathecal meningitis instructions conflict with a simultaneous oral-route statement: 500000 IU in 10 mL saline, 20000 IU daily then 25000 IU every other day. This local procedure requires route clarification and is not represented as IV or oral dosing.
Ophthalmic polymyxin B provides gram-negative activity and is combined with other antibacterials for broader coverage. Local hypersensitivity is possible; no numeric ocular application schedule is specified here.