Colistin

Polymyxin·Infectious Diseases - Other Antibiotics

Life-threatening infections caused by MDR Gram-negatives (Pseudomonas, Acinetobacter, Klebsiella) resistant to all other antibiotics

POLYMYXINColymycinVials (Colistimethate sodium…S4TGA

Max Dose

Calculated in IU

Half-life

14 h

Nephrotoxicity

CRITICAL

Neurotoxicity

HIGH RISK

Rapid Summary

Overview

Polymyxin E. An ancient, highly toxic antibiotic resurrected as the absolute last line of defense against Multi-Drug Resistant (MDR) Gram-negative superbugs (e.g., Carbapenem-Resistant Enterobacteriaceae).

Maximum Dose

Calculated strictly in Millions of International Units (IU) based on renal function.

Clinical Focus

Devastates the kidneys and nervous system. Acts literally like a biological detergent, tearing apart the bacterial cell membrane.

Bottom Line

Colistin is a last-resort polymyxin for extensively drug-resistant gram-negative infections, but causes significant nephrotoxicity and neurotoxicity and is reserved for when no alternatives exist.

Formulation & Access

Brand Names

Colymycin

Parenteral

Vials (Colistimethate sodium, CMS) for IV infusion. CMS is an inactive prodrug that slowly converts to active colistin in the blood.

Prescribing & PBS

Hospital ICU/ID supply only. Strictly restricted.

Indications & Use

Primary

TGA

Life-threatening infections caused by MDR Gram-negatives (Pseudomonas, Acinetobacter, Klebsiella) resistant to all other antibiotics.

Clinical Place

The absolute last resort. Used only when the lab reports 'Resistant to Everything Except Colistin'.

Quick reference

Class & Role

Polymyxin — Polymyxin E.

Route / Formulation

Vials (Colistimethate sodium, CMS) for IV infusion. CMS is an inactive prodrug that slowly converts to active colistin in the blood. (Colymycin)

Usual Dose & Max

IV 9 Million IU STAT over 1-2 hours (Specialist critical care only). Calculated strictly in Millions of International Units (IU) based on renal function.

Key Indication Doses

MDR Sepsis (Loading): IV 9 Million IU STAT over 1-2 hours (Specialist critical care only). Maintenance: IV 4.5 Million IU BD (12-hourly). Inhaled (CF / Vent-Associated Pneumonia): Inhaled 1-2 Million IU via nebuliser BD or TDS. Renal Impairment: Massive dose reductions required if eGFR < 50. Handled by highly specialized nomograms.

Best Uses

Colistin is a last-resort polymyxin for extensively drug-resistant gram-negative infections, but causes significant nephrotoxicity and neurotoxicity and is reserved for when no alternatives exist.

Avoid / Cautions

Myasthenia Gravis (guaranteed respiratory paralysis). Pregnancy Category B3. (Used if maternal life is at immediate risk from MDR sepsis).

Key Risks

Renal: Acute Tubular Necrosis, severe AKI (occurs in up to 50% of patients treated systemically). Neurological: Perioral paresthesia, dizziness, confusion, ataxia. CRITICAL — Neuromuscular blockade leading to respiratory paralysis/apnoea. Respiratory: Severe bronchospasm (if given via nebuliser without prior bronchodilator).

Key Interactions

Neuromuscular blocking agents (Rocuronium) and Aminoglycosides. The combination causes prolonged, fatal respiratory muscle paralysis. Nephrotoxins (NSAIDs, Vancomycin). Synergistic kidney destruction.

Monitoring

Strict daily U&E and eGFR monitoring. Renal function often deteriorates rapidly during the course. Monitor RR and neuromuscular strength. If nebulising, give Salbutamol 15 mins prior to prevent severe airway spasm.

Clinical Pearl

Because it is administered as the inactive prodrug CMS, it takes hours for active colistin levels to rise in the blood. In fulminant septic shock, this delay is lethal, which is why a massive 9 Million IU Loading Dose is mandatory to try and saturate the blood quickly.

Access

Colymycin

Brand: Colymycin

Colistin

Polymyxin·Infectious Diseases - Other Antibiotics

Life-threatening infections caused by MDR Gram-negatives (Pseudomonas, Acinetobacter, Klebsiella) resistant to all other antibiotics

POLYMYXINColymycinVials (Colistimethate sodium…S4TGA

Max Dose

Calculated in IU

Half-life

14 h

Nephrotoxicity

CRITICAL

Neurotoxicity

HIGH RISK

Rapid Summary

Overview

Maximum Dose

Calculated strictly in Millions of International Units (IU) based on renal function.

Clinical Focus

Devastates the kidneys and nervous system. Acts literally like a biological detergent, tearing apart the bacterial cell membrane.

Bottom Line

Colistin is a last-resort polymyxin for extensively drug-resistant gram-negative infections, but causes significant nephrotoxicity and neurotoxicity and is reserved for when no alternatives exist.

Formulation & Access

Brand Names

Colymycin

Parenteral

Vials (Colistimethate sodium, CMS) for IV infusion. CMS is an inactive prodrug that slowly converts to active colistin in the blood.

Prescribing & PBS

Hospital ICU/ID supply only. Strictly restricted.

Indications & Use

Primary

TGA

Life-threatening infections caused by MDR Gram-negatives (Pseudomonas, Acinetobacter, Klebsiella) resistant to all other antibiotics.

Clinical Place

The absolute last resort. Used only when the lab reports 'Resistant to Everything Except Colistin'.

Quick reference

Class & Role

Polymyxin — Polymyxin E.

Route / Formulation

Vials (Colistimethate sodium, CMS) for IV infusion. CMS is an inactive prodrug that slowly converts to active colistin in the blood. (Colymycin)

Usual Dose & Max

IV 9 Million IU STAT over 1-2 hours (Specialist critical care only). Calculated strictly in Millions of International Units (IU) based on renal function.

Key Indication Doses

Best Uses

Colistin is a last-resort polymyxin for extensively drug-resistant gram-negative infections, but causes significant nephrotoxicity and neurotoxicity and is reserved for when no alternatives exist.

Avoid / Cautions

Myasthenia Gravis (guaranteed respiratory paralysis). Pregnancy Category B3. (Used if maternal life is at immediate risk from MDR sepsis).

Key Risks

Key Interactions

Monitoring

Clinical Pearl

Access

Colymycin

Brand: Colymycin