Colistimethate (Injection)

Colistimethate is a medicine given intravenously (IV) or intramuscularly (IM) in the treatment of adults and children, including newborns, with different types of bacterial infections.


Colistimethate medicinal solution is injected into a vein (IV) or into a muscle (IM), usually on the buttocks or thigh, when treating patients with certain bacterial infections. In some cases, the medicine is given as a constant infusion through a vein, for a duration of time. It is usually given by a nurse or trained healthcare professional at a hospital or medical center.

The antibiotic works by killing and preventing further growth of the infectious bacteria. Like other antibiotics, Colistimethate works best when it is kept at the desired level in the body. Patients should take their treatment exactly as directed to prevent the condition from getting worse or becoming resistant to antibiotics.

One of the important benefits of this antibiotic medication is its safety and efficacy in treating neonatal infections caused by multidrug-resistant gram-negative bacteria.

The use of this injection is limited in patients with certain medical problems and who are using other medications that may cause an adverse interaction. Any decision to treat them should be done with due caution.

Colistimethate is available in the US under the brand names, Coly-Mycin M and Coly-Mycin M Parenteral. It is recommended for treating only certain bacterial infections and will not work if used to treat colds, flu or other viral infections.

Condition treated

  • Bacterial infections

Type of medicine

  • Cyclopeptide antibiotic

You should consider the potential benefits and risks of using Colistimethate. Your doctor may help you decide if it is safe for you.

Tell your doctor if you are allergic to the medicine, or have had an unusual reaction to it. Some patients may also be allergic to inactive ingredients in the medication. In discussing allergies, tell your doctor of any allergy you may have to foods, preservatives, dyes or animals.

Certain medications or medical conditions may affect the way the injection should work. Tell your doctor about all medications you are taking or plan to take. These include prescription and over-the-counter medicines (OTCs), vitamins, nutritional supplements, and herbal products.

Patients with kidney disease, severe liver disease, or diarrhea should not take this medication. If it cannot be avoided, then the medicine should be taken with caution, as determined by a doctor.

Side Effects

Serious side effects

Call your nurse or doctor right away if you experience any of the following symptoms. They may be signs of a serious side effect.

  • style="font-weight: 400;">decreased urination
  • tingling or numbness of the arms, hands, legs, feet or tongue
  • feeling a crawling sensation under the skin
  • itching
  • slow or slurred speech
  • muscle weakness
  • breathing that is slow or shallow (or temporarily stops)
  • diarrhea that is bloody or watery (severe) that occurs after treatment ends

The following other side effects may occur, but their incidence is not known. Call your doctor right away if you experience any of them.

Incidence unknown

  • drowsiness
  • bloodstained urine
  • decreased or increased urination or amount of urine
  • tightness in the chest
  • burning or prickling sensation of the skin
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  • excessive thirst
  • wheezing
  • nausea or vomiting
  • bluish lips or skin
  • swelling of the lower legs or feet
  • weakness
  • loss of appetite

Some side effects that occur go away on their own. They generally do not require medical attention. If they become worse, bothersome or do not go away, tell your doctor. Some of these effects include the following:

Incidence unknown

  • feeling as if you are spinning
  • feeling dizzy or lightheaded
  • feeling as if you or your surroundings are moving
  • itchiness
  • redness of the skin
  • diarrhea
  • pain or cramps in the stomach
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Other side effects not mentioned in this guide may occur. Talk to your doctor or healthcare professional if you experience any unusual symptom that becomes bothersome or gets worse. You may call the FDA at 1-800-FDA-1088 to report side effects.


Colistimethate injection is made from a powder that is mixed with a liquid to form a solution.
Patients allergic to this medicine should not be treated with it. Your doctor should immediately stop treating you with this drug if you develop an allergic reaction to it.

For treating bacterial infections

Your dose may be different from another patient. The strength of each dose, how often you take it, the time between each dose, and the entire duration of your treatment may be based on your age, type of infection being treated, the presence of other medical problems, and your body's response to the first dose.

Adults: The injection may not be prescribed for you to take at home. It is given into one of your veins or into a muscle by a nurse or healthcare professional, usually at a hospital or clinic. The medicine may also be given as a constant infusion through a vein.

Children: Dose will be determined by your doctor.

Geriatrics: The safety and efficacy of the drug are established for use in elderly patients. However, these patients are more likely to have age-related kidney problems when treated with this drug. Dose may vary based on age, as determined by your doctor.

Pregnant or breastfeeding women: Tell your doctor if you are pregnant or breastfeeding. To avoid any risk of harm to an unborn baby or breastfeeding infant, use and dose must be determined by your doctor.

Missed dose

If you miss a scheduled dose of the injection, speak with your doctor or healthcare professional immediately so you can set up a new dosing schedule.


Get emergency help right away if you experience any of the following symptoms of an overdose:

  • shaky or unsteady walk
  • mood or mental changes
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  • uncontrolled eye movements
  • lack of muscle coordination, such as trembling
  • feeling unusually drowsy, tired, weak, dull or sluggish


Other medicines

Certain drugs are not recommended to be used while taking Colistimethate. This is because they can adversely interact and increase the risk of certain side effects. In cases where it is necessary to use them, precaution must be taken by your doctor to ensure all your medications are taken safely.

The antibiotic injection is usually not recommended for use with the following medicines. If it necessary to use any of them during treatment for continued health, your doctor may change the dose or how often you use any of your medicines.

  • Capreomycin
  • Tobramycin
  • Gentamicin
  • Neomycin
  • Amikacin
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  • Paromomycin
  • Kanamycin
  • Streptomycin

There is a possibility for an increased risk of certain side effects if any of the following other drugs are used during your treatment. If their use during your antibiotic therapy is best for your health, your doctor may change the dose or how often you use any of your medications.

  • Rapacuronium
  • Alcuronium
  • Pipecuronium
  • Mivacurium
  • Doxacurium
  • Fazadinium
  • Vecuronium
  • Pancuronium
  • Metocurine
  • Atracurium
  • Rocuronium
  • Tubocurarine
  • Cisatracurium
  • Gallamine
  • Hexafluorenium

Other drugs that may cause adverse interaction are as follows. Your doctor should use them with caution while treating you for bacterial infection. This may include changing the dose or how often you use any of them.

  • Tobramycin
  • Amphotericin B
  • Polymyxin B
  • Vancomycin
  • Neomycin
  • Sodium Citrate (in Bicitra)

Food, alcohol, and tobacco

You may ask your doctor about restrictions on your use of certain foods, alcohol or tobacco during treatment. Foods and other substances may affect the way a drug is intended to work or can increase the risk of side effects. Additionally, certain medicines are required to be taken with or without food.

Other medical problems

The existence of other medical problems is known to cause interaction with Colistimethate. You must tell your doctor if you have any other medical conditions. The antibiotic may make the following conditions worse:

  • Lung disease (severe)

The medication should be used with caution in patients with the following condition. This is because it slows the removal of the medicine from the body and increases the chance for side effects.

  • Kidney disease

The benefit of prolonged treatment with this drug should be balanced against the potential risk of renal failure in patients with kidney disease.

Other medicines not mentioned here may also interact with the injection when used together during treatment.


  • Do not use this medicine if you are allergic to it.
  • Do not stop using the medicine until the treatment cycle is completed, even if you begin to feel better after a few days of using it.
  • Call your doctor, nurse or healthcare professional if your symptoms do not improve within a few days, or if they become worse.
  • This medication may make some patients dizzy. To avoid accident or injury, do not drive a car or operate machinery until you know how this medication affects you.
  • Avoid using alcohol as it can cause serious dizziness.
  • The medicine is known to cause diarrhea. Do not take any medicine to treat diarrhea, unless approved by your doctor.
  • Unless your doctor decides it is best for you, do not take the antibiotic if you are using other medicines or have a medical problem that may adversely interact with it.


This injectable solution is usually stored by a healthcare professional at a hospital or medical center.


Colistimethate injectable medicine is safe and effective for use in adults and children. It is even safe for use in newborn babies with neonatal infections caused by multidrug-resistant gram-negative bacteria.

For the drug to be fully effective, patients are required to take all their doses strictly as scheduled, until the treatment is complete. This ensures the infectious bacteria is killed and reduces the chance of the infection coming back.

Prolong use of the medicine in patients with kidney disease can lead to kidney failure. Therefore, the potential benefits should be carefully weighed against the potential risks of using it.

The known side effects caused by the medicine are not many when compared to other drugs. However, some of the side effects can be serious and may require medical attention. Despite the antibiotic may interact with other medicines or existing medical problems, it can be safely used as determined by a doctor.