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Polymyxin E (Generic Colistimethate Injection)

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Why is this medication prescribed?

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.

How should this medicine be used?

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.

You may receive colistimethate injection in a hospital or you may administer the medication at home. If you will be receiving colistimethate injection at home, your healthcare provider will show you how to use the medication. Be sure that you understand these directions, and ask your healthcare provider if you have any questions.

You should begin to feel better during the first few days of treatment with colistimethate injection. If your symptoms do not improve or get worse, call your doctor.

Use colistimethate injection until you finish the prescription, even if you feel better. If you stop using colistimethate injection too soon or skip doses, your infection may not be completely treated and the bacteria may become resistant to antibiotics.

Other uses for this medicine

Colistimethate injection is also sometimes inhaled by mouth using a nebulizer (machine that turns medication into a mist that can be inhaled) to treat certain serious lung infections. Talk to your doctor about the risks of using this medication for your condition.

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

What special precautions should I follow?

Before using colistimethate injection,

  • Tell your doctor and pharmacist if you are allergic to colistimethate, any other medications, or any of the ingredients in colistimethate injection. Ask your pharmacist for a list of the ingredients.
  • Tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: amikacin, amphotericin B (Abelcet, Ambisome), capreomycin (Capastat), gentamicin (Gentak, Genoptic), kanamycin, neomycin (Neo-Fradin), paromomycin, polymyxin B, sodium citrate (in Bicitra), streptomycin, tobramycin (Tobi, Tobrex), or vancomycin (Vancocin). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
  • Tell your doctor if you have or have ever had kidney disease.
  • Tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. If you become pregnant while receiving colistimethate injection, call your doctor.
  • If you are having surgery, including dental surgery, tell the doctor or dentist that you are receiving colistimethate injection.
  • You should know that colistimethate injection may make you dizzy or affect your coordination. Do not drive a car or operate machinery until you know how this medication affects you.

What special dietary instructions should I follow?

Unless your doctor tells you otherwise, continue your normal diet.

What side effects can this medication cause?

Colistimethate injection may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • Upset stomach
  • Hives
  • Rash

Some side effects can be serious. If you experience any of these symptoms, call your doctor immediately or get emergency medical treatment:

  • Numbness and tingling of the arms, legs, hands, feet, or tongue
  • Sensation of insects crawling under the skin
  • Itching
  • Slurred speech
  • Muscle weakness
  • Shallow, slowed, or temporarily stopped breathing
  • Decreased urination
  • Severe diarrhea (watery or bloody stools) with or without fever and stomach cramps that may occur up to 2 months or more after your treatment

Colistimethate injection may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online ( or by phone (1-800-332-1088).

In case of emergency/overdose

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services at 911.

Symptoms of overdose may include the following:

  • Numbness and tingling
  • Extreme tiredness
  • Confusion
  • Dizziness
  • Loss of balance and coordination
  • Rapid, uncontrolled eye movements
  • Difficulty speaking
  • Slow, shallow, or difficult breathing
  • Decreased urination

What other information should I know?

Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your body’s response to colistimethate injection.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

Brand names

  • Coly-Mycin M®
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