Colomycin injection (Colistin)

How does it work?

Colomycin injection contains the active ingredient colistimethate sodium, which is a type of medicine known as a polymyxin antibiotic. It is used to treat infections with bacteria. (Colistimethate sodium is also sometimes called colistin sulfomethate sodium.)

Colistimethate works by binding to the cell membrane of bacteria cells. The cell membranes of bacteria are vital for their survival. They keep unwanted substances from entering their cells and stop the contents of their cells from leaking out. Colistimethate damages the cell membrane and allows holes to appear in the cell walls. This kills the bacteria.

Colistimethate sodium is not absorbed from the gut so can't be taken by mouth to treat systemic infections. It is given by injection into a vein to treat serious infections caused by Gram-negative bacteria, including Pseudomonas aeruginosa, Acinetobacter baumanii and Klebsiella pneumoniae. Colistimethate is only used when other antibiotics are ineffective because the bacteria causing the infection are resistant to other antibiotics.

Colistimethate is given by inhalation to treat Pseudomonas aeruginosa infection of the lungs in people with the lung condition cystic fibrosis. In this case the injection solution is inhaled into the lungs from a machine called a nebuliser. This machine converts the liquid medicine into tiny particles that can be breathed into the lungs. This allows the antibiotic to penetrate the lung secretions and act directly in the area of infection.

What is it used for?

  • Colomycin is given by injection to treat serious infections caused by Gram-negative bacteria, including chest infections and urinary tract infections, that have not responded to treatment with other antibiotics.
  • Colomycin injection solution is inhaled via a nebuliser to treat Pseudomonas aeruginosa lung infection in people with cystic fibrosis.

How is this treatment given?

  • Colomycin may be given by injection or drip (infusion) into a vein. It can also be given through a nebuliser for inhalation.
  • The dose needed depends on the age, weight and kidney function of the patient and the severity of the infection. A drip of colistimethate is usually given over 30 minutes. This is repeated three times a day.
  • If colistimethate is given by inhalation it is usually given twice a day.


  • During treatment with this medicine you will need to have regular blood tests to monitor the level of the medicine in your blood. This is to make sure that your dose is not too high to cause side effects, or too low to be effective against the infection.
  • Antibiotics can sometimes cause inflammation of the bowel (colitis). For this reason, if you get diarrhoea that becomes severe or persistent or contains blood or mucus, either during or after treatment with this medicine, you should consult your doctor immediately.

Use with caution in

  • People with decreased kidney function.
  • Hereditary blood disorders called porphyrias.

Not to be used in

  • People who are allergic to the antibiotic polymyxin B.
  • People with abnormal muscle weakness (myasthenia gravis).

This medicine should not be used if you are allergic to any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

  • The safety of this medicine for use during pregnancy has not been established. It is not recommended for use during pregnancy, unless the expected benefit to the mother is greater than any possible risk to the developing baby. Seek medical advice from your doctor.
  • This medicine passes into breast milk in small amounts. It should be used with caution in breastfeeding mothers and only if the expected benefit to the mother is greater than any possible risk to the nursing infant. Seek medical advice from your doctor.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.

When given by infusion or injection

  • Breathing difficulties. Tell your doctor straight away if you experience this.
  • Reaction at the site of injection or infusion.
  • Pins and needles sensations (paraesthesia).
  • Dizziness.
  • Spinning sensation (vertigo).
  • Fainting.
  • Flushing.
  • Visual disturbances.
  • Slurred speech.
  • Confusion.
  • Kidney problems.

When given by inhalation

  • Cough.
  • Sore throat.
  • Sore mouth.
  • Thrush infections of the mouth or throat.
  • Narrowing of the airways that causes difficulty in breathing (bronchospasm).

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.

For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while being treated with this one, to make sure that the combination is safe.

There may be an increased risk of side effects on the kidneys if this medicine is used in combination with other medicines that can affect kidney function, such as the following:

  • aminoglycoside antibiotics such as gentamicin, tobramycin and amikacin
  • amphotericin
  • capreomycin
  • cephalosporin antibiotics, eg cephaloridine
  • ciclosporin
  • cisplatin
  • polymixin
  • tacrolimus
  • teicoplanin
  • vancomycin.

Colistimethate sodium may oppose the effects of neostigmine and pyridostigmine used to treat the muscular condition myasthenia gravis.

Oral typhoid vaccine (Vivotif) should not be taken until at least three days after you have finished a course of this antibiotic, because the antibiotic could make this vaccine less effective.

Other medicines containing the same active ingredient

  • Colomycin tablets
  • Promixin.

Colistimethate injection is also available generically (ie without a brand name).