Colistimethate injection is used to treat certain infections caused by bacteria. Colistimethate injection is in a class of medications called antibiotics. It works by killing bacteria.

Antibiotics such as colistimethate injection will not work for colds, flu, or other viral infections. Using antibiotics when they are not needed increases your risk of getting an infection later that resists antibiotic treatment.

Colistimethate injection comes as a powder to be mixed with a liquid and injected intravenously (into a vein) over a period of 3 to 5 minutes. Colistimethate injection may also be injected into the muscles of the buttocks or thighs. It is usually given every 6 to 12 hours. Colistimethate injection may also be given as a constant intravenous infusion over 22 to 23 hours. The length of your treatment depends on your general health, the type of infection that you have, and how well you respond to the medication.