Colistin

Class: Polymyxin antibiotic

Mechanism of Action: Disrupts bacterial cell membrane of Gram-negative bacteria, causing leakage of cellular contents and bacterial death.

Indications

• Multidrug-resistant Gram-negative infections (Pseudomonas, Acinetobacter, Klebsiella)
• Severe urinary tract infections
• Sepsis due to resistant Gram-negative bacteria
• Respiratory infections (ventilator-associated pneumonia, cystic fibrosis)

Dosage

• Adults (IV): Loading dose: 9 million IU, then 4.5 million IU every 12 hours (adjust for renal function)
• Children: 75,000–150,000 IU/kg/day IV divided every 12–24 hours
• Dosage should always be individualized based on renal function and infection severity

Maximum Dose

Depends on renal function; typically not exceeding 9–10.5 million IU/day IV in adults

Major Side Effects

• Nephrotoxicity (most common)
• Neurotoxicity (paresthesia, dizziness, ataxia, neuromuscular blockade)
• Allergic reactions (rash, fever)
• GI disturbances (nausea, vomiting)

Contraindications

• Hypersensitivity to colistin or polymyxin
• Use with caution in patients with pre-existing renal impairment

Compatible Fluids

• 0.9% Sodium Chloride
• 5% Dextrose

Route of Administration

• Intravenous (IV) infusion
• Inhalation (nebulization for respiratory infections)
• Topical (limited use in wound infections)

Type of Administration

• IV: slow infusion over 30–60 minutes
• Inhalation: nebulized as per respiratory infection protocol
• Topical: apply to affected area as directed

Special Precautions

• Monitor renal function daily during therapy
• Adjust dose in renal impairment
• Monitor for signs of neurotoxicity
• Use cautiously in elderly and critically ill patients
• Avoid concomitant nephrotoxic drugs if possible