Colistin (Polymyxin E): veterinary dose and monograph

At a glance

Drug class

Antibiotic

Also known as

Polymyxin E, Colistin sulphate, Colistimethate sodium

Species with doses

Cattle, Pigs and Poultry

Routes

PO

Last reviewed

1 October 2026

Indications

• Enteric colibacillosis / Gram-negative enteritis (oral, local — where still legally permitted, individual animals)
• Last-resort therapy of multidrug-resistant Gram-negative systemic infection (parenteral, rare)

Colistin (Polymyxin E) dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• No reference dose for this species: Neither Papich 5e nor Plumb’s has a colistin (polymyxin E) monograph, and there is no companion-animal label dose. Colistin is a WHO highest-priority critically important antimicrobial — reserve use.

Cats

• No reference dose for this species: Neither Papich 5e nor Plumb’s has a colistin (polymyxin E) monograph, and there is no companion-animal label dose. Colistin is a WHO highest-priority critically important antimicrobial — reserve use.

Cattle

• Calf enteric infection (oral, restricted): IU/kg. Label-sourced — neither Papich 5e nor Plumb’s has a colistin monograph. Individual animal therapy only, where permitted. Follow the local label withdrawal.

Pigs

• Enteric colibacillosis (oral, individual treatment where permitted): IU/kg. Product-label dose — neither Papich 5e nor Plumb’s has a colistin monograph. Individual therapy only where permitted; not for prophylaxis or growth promotion (banned for these uses in India). Follow the local label withdrawal.

Poultry

• Colibacillosis (oral, restricted): IU/kg. Label-sourced — neither Papich 5e nor Plumb’s has a colistin monograph. Therapeutic use only where permitted; not for prophylaxis or growth promotion (banned for these uses in India). Follow the local label withdrawal.

Buffalo

No buffalo-specific doses are on file, so buffalo are dosed as cattle.

• Calf enteric infection (oral, restricted): IU/kg. Label-sourced — neither Papich 5e nor Plumb’s has a colistin monograph. Individual animal therapy only, where permitted. Follow the local label withdrawal.

Contraindications

Renal impairment (systemic forms). Prohibited as a growth promoter / routine prophylactic in food animals in India and many countries. Avoid systemic use except as a documented last-resort against multidrug-resistant Gram-negatives. Concurrent nephrotoxins/neuromuscular blockers.

Species-specific warnings

Cattle: Mass medication / metaphylaxis is banned in India. Permit only individual-animal therapeutic use with withdrawal observed.

Birds: Flock/feed use prohibited — major source of transferable mcr resistance entering the food chain.

Adverse effects

• Nephrotoxicity (dose-related, systemic use)
• Neurotoxicity — paraesthesia, neuromuscular blockade, apnoea (systemic)
• Disruption of gut flora (oral)
• Selection of mcr-mediated transferable resistance — public-health hazard

Drug interactions

• Aminoglycosides, amphotericin B, NSAIDs: additive nephrotoxicity
• Neuromuscular blockers / anaesthetics: potentiated, dangerous neuromuscular blockade (systemic)
• Other neurotoxins: additive neurotoxicity

Pregnancy and lactation

Safety data limited; oral use gives minimal systemic exposure. Avoid systemic colistin in pregnancy unless no alternative for a resistant infection.

Monitoring

• Renal function closely during any systemic use
• Neurological status (weakness, respiratory effort)
• Strict justification and record-keeping — restricted antimicrobial
• Adherence to legal restrictions on food-animal use

Toxicity and overdose

Systemic colistin is dose-limited by nephrotoxicity (acute tubular injury) and neurotoxicity (paraesthesia, ataxia, respiratory muscle paralysis/apnoea). Oral use is locally tolerated but the dominant "toxicity" is ecological — driving spread of mobile colistin resistance that threatens human medicine.

Management: No specific antidote. Discontinue; supportive care. For neuromuscular blockade/apnoea provide assisted ventilation (anticholinesterases are unreliable for polymyxin blockade). IV fluids and renal support; haemodialysis is of limited benefit.

Clinical pearls

• Treat colistin as a last-resort drug, not a routine gut antibiotic — its human importance outweighs convenience
• India prohibits colistin in animal feed / as a growth promoter (2019 gazette) — only individual therapeutic use where legal
• Oral colistin is poorly absorbed and acts in the gut lumen; systemic (colistimethate) use is reserved for MDR human-style cases
• Always pair use with culture, justification, and stewardship documentation

Mechanism of action

Cationic polymyxin that binds the lipid-A component of lipopolysaccharide in the Gram-negative outer membrane, displacing divalent cations and disrupting membrane permeability — a detergent-like, concentration-dependent bactericidal effect that causes leakage of cell contents. Resistance arises by LPS modification, including the transferable mcr genes.

Formulations and products

• Oral powder/solution (gut, IU-based)
• Colistimethate 1 MIU vial (systemic, human)
• Colistin sulphate oral (Various (India, restricted)) — IU-based oral powder/solution, Oral powder / solution
• Xylistin — Colistimethate sodium 1 / 2 MIU vial, Injection (reconstitute) (human-label)
• Walamycin / Colistin — Colistin sulphate oral suspension, Oral suspension (human-label)

Storage

Oral powders: 15–30 °C, dry. Reconstituted colistimethate: refrigerate and use promptly per label.

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Other antibiotics

• Ciprofloxacin
• Clarithromycin
• Clindamycin
• Cloxacillin
• Danofloxacin
• Doxycycline
• Enrofloxacin
• Erythromycin

Frequently asked questions