Treatment of infections due to sensitive strains of certain gram-negative organisms including Enterobacter aerogenes, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa.

Colistin (polymyxin E) is a surface-active agent, which penetrates into and disrupts the bacterial cell membrane, changes its permeability. It has bactericidal activity against G(-) bacteria. Colistin has come into recent use for treating multidrug-resistant Acinetobacter infection, although resistant forms have been reported

Distribution:
1. CSF penetration: ~5%
2. Vd (of colistin active form):
(1) Healthy volunteer: 12.4 L
(2) Critically ill: 7.2-189 L
3. Protein binding: 50%
4. Dialyzable (~30%), administer after dialysis
Metabolism:
Colistimethate sodium (inactive prodrug) is hydrolyzed to colistin (active form). [Only ~30% is converted to colistin]
Half-life elimination:
1. Colistimethate: 2 to 3 hours
2. Colistin:
(1) Critically ill: 14.4 hours
(2) Cystic fibrosis: ~4 hours
(3) ESRD patients receiving CAPD: 13.2 hours
Time to peak:
1. Healthy volunteers: 2 hours (range: 1-4 hours)
2. Critically ill: ~7 hours
Excretion:
Primarily urine (as unchanged drug); most colistin recovered in the urine is from postexcretion hydrolysis of colistimethate sodium

Hypersensitivity to colistin or any components of the product

C
Adverse events have been observed in animal reproduction studies. Colistimethate crosses the placenta in humans.

Nephrotoxicity; neurotoxicity including circumoral paresthesias or numbness, tingling or formication of the extremities, generalized pruritus, vertigo, dizziness and slurring of speech.