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Overview: Colistimethate is an antibiotic that is used for infections caused by certain bacteria. Common side effects include dizziness and tingling or numbness in your arms or legs. Do not drive or use dangerous machinery while you are using this medicine. If you get diarrhea even up to two months after stopping colistimethate or are making less urine (pee), call your health care provider right away.

Uses

What is colistimethate used for?

Colistimethate is an antibiotic that is commonly used for infections caused by certain gram-negative bacteria.

Colistimethate may also be used for other conditions as determined by your health care provider.

Colistimethate may not be right for some infections, depending on which germs are causing the infection. Bacteria in some locations may have developed resistance to colistimethate, which will make it not work as well.

How does colistimethate work (mechanism of action)?

Colistimethate kills certain types of bacteria by damaging their cell membrane.

How is colistimethate supplied (dosage forms)?

Brands and other names

  • Coly-Mycin M

Dosage forms and strengths

Colistimethate is available in an injectable form that is given by a health care provider.

How should I store colistimethate?

Colistimethate is usually given by a health care provider in a hospital or clinic. If you will store colistimethate at home, follow the instructions given by your health care provider.

Side Effects

What are the most common side effects of colistimethate?

The most common side effect of colistimethate is nerve problems (see below). Tell your health care provider if you have any of these side effects that bother you.

There may be other side effects of colistimethate that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of colistimethate?

While less common, the most serious side effects of colistimethate are described below, along with what to do if they happen.

Severe Allergic Reactions. Colistimethate may cause allergic reactions, which can be serious. Stop using colistimethate and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives, which can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Nerve Problems. Colistimethate may cause nerve problems. Do not drive or do other activities that require alertness or coordination while you are using colistimethate. Tell your health care provider right away if you have any of the following symptoms.

  • Tingling, prickling, burning, numbness, or other unusual sensations in your arms or legs
  • Itching
  • Feeling off balance or dizziness
  • Slurring of speech

Kidney Damage. Kidney damage can happen when taking colistimethate. Call your health care provider right away if you have any of the following symptoms of kidney damage.

  • Reduced need to pee
  • Swelling in your feet, ankles, or legs
  • Weakness or unusual tiredness
  • Difficulty catching your breath or chest pain/pressure
  • Confusion
  • Nausea
  • Seizures

Muscle Weakness. Colistimethate may cause muscle weakness. In some cases, this may affect your breathing muscles, leading to breathing problems. Tell your health care provider right away if you get muscle weakness. Get emergency help if you have trouble breathing.

Antibiotic-Associated Diarrhea. An overgrowth of germs called Clostridioides difficile, or “C. diff,” can happen in your gut with many types of antibiotics, including colistimethate. This can cause a condition known as antibiotic-associated diarrhea, which can happen even up to two months after stopping the antibiotic. Call your health care provider right away if you have any of the following symptoms of this condition.

  • Watery diarrhea
  • Diarrhea that does not go away
  • Blood in your stool (poop)
  • Severe stomach cramps
  • Fever that starts after you start or finish the medicine

Warnings & Precautions

Who should not use colistimethate?

Allergies to Ingredients. People who are allergic to any of the following should not use colistimethate.

  • Colistimethate
  • Coly-Mycin M
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific colistimethate products they stock.

What should I know about colistimethate before using it?

Colistimethate is usually given by a health care provider in a hospital or clinic.

Colistimethate can affect your alertness or coordination. Do not drive or do other activities that require alertness or coordination while you are using this medicine.

What should I tell my health care provider before using colistimethate?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if colistimethate is right for you.

In particular, make sure that you discuss any of the following.

Other Medicines and Supplements. Colistimethate may interact with other medicines and supplements. Before using colistimethate, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Kidney Problems. People with kidney problems may be at a higher risk for certain side effects of colistimethate. Tell your health care provider if you have or have had any problems with your kidneys.

Pregnancy. It is not known if or how colistimethate could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant. Your health care provider will let you know if you should use colistimethate while you are pregnant or trying to get pregnant.

Breastfeeding. It is not known if colistimethate passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should use colistimethate while breastfeeding.

Interactions

Does colistimethate interact with foods or drinks?

There are no known interactions between colistimethate and foods or drinks.

It is unknown if drinking alcohol will affect colistimethate, but heavy drinking can slow your immune response and make it harder for your body to fight infection. Also, the risk of dizziness may increase if you drink alcohol while taking colistimethate.

Does colistimethate interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before using colistimethate.

  • An aminoglycoside antibiotic, such as amikacin or gentamicin, which is given by injection to treat certain infections
  • Polymyxin B, which is a medicine given by injection to treat certain infections

This may not be a complete list of medicines that can interact with colistimethate. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much colistimethate?

If you or someone else has used too much colistimethate, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of colistimethate?

Colistimethate is usually given by a health care provider in a hospital. Your health care provider will make sure you are receiving colistimethate as scheduled. If you miss an appointment to get your colistimethate dose, call to make another appointment as soon as possible.

It is important to complete your prescribed course of colistimethate, even if your symptoms get better or go away. This will reduce the risk that future infections are resistant to colistimethate or other similar medicines.